MAX11800

19-4711; Rev 2; 3/10 Low-Power, Ultra-Small Resistive Touch-Screen Controllers with I2C/SPI Interface General Description The MAX11800–MAX11803 low-power touch-screen controllers operate from a single supply of 1.70V to 3.6V, targeting power-sensitive applications such as handheld equipment. The devices contain a 12-bit SAR ADC and a multiplexer to interface with a resistive touch-screen panel. A digital serial interface provides communications. The MAX11800–MAX11803 include digital preprocessing of the touch-screen measurements, reducing bus loading and application-processor resource requirements. The included smart interrupt function generator greatly reduces the frequency of interrupt servicing to the devices. The MAX11800–MAX11803 enter low-power modes automatically between conversions to save power, making the devices ideal for portable applications. The MAX11800/MAX11801 offer two modes of operation: direct and autonomous. Direct mode allows the application processor to control all touch-screen controller activity. Autonomous mode allows the MAX11800/MAX11801 to control touch-screen activity, thereby freeing the application processor to perform other functions. In autonomous mode, the devices periodically scan the touch screen for touch events without requiring hostprocessor intervention. This can be used to reduce system power consumption. An on-chip FIFO is used during autonomous mode to store results and increase effective data throughput and lower system power. The MAX11800–MAX11803 support data-tagging, which records the type of measurement performed; X, Y, Z1, or Z2, and the type of touch event; initial touch, continuing touch, or touch release. The MAX11800/MAX11802 support the SPI™ serial bus. The MAX11801/MAX11803 support the I2C serial bus. The MAX11800–MAX11803 are available in 12-pin TQFN and 12-pin WLP packages, and are specified over the -40°C to +85°C (extended) and -40°C to +105°C (automotive) temperature ranges. Features ♦ 4-Wire Touch-Screen Interface ♦ X/Y Coordinate and Touch Pressure Measurement ♦ Ratiometric Measurement ♦ ♦ ♦ ♦ 12-Bit SAR ADC Single 1.7V to 3.6V Supply Two Operating Modes—Direct and Autonomous Data Tagging Provides Measurement and Touch Event Information ♦ Data Filtering Provides Noise Reduction ♦ Aperture Mode† Provides Spatial Filtering ♦ Digital Processing Reduces Bus Activity and Interrupt Generation ♦ Programmable Touch-Detect Pullup Resistors ♦ Auto Power-Down Control for Low-Power Operation ♦ 25MHz SPI Interface (MAX11800/MAX11802) ♦ 400kHz I2C Interface (MAX11801/MAX11803) ♦ 1.6mm x 2.1mm, 12-Pin WLP and 4mm x 4mm, 12-Pin TQFN ♦ Low-Power Operation 343µW at VDD = 1.7V, 34.4ksps 888µW at VDD = 3.3V, 34.4ksps ♦ ESD Protection ±4kV HBM ±8kV HBM (X+, X-, Y+, Y-) ±1kV CDM ±200V MM MAX11800–MAX11803 Ordering Information PART MAX11800ETC+ MAX11800GTC/V+ MAX11800EWC+T MAX11801ETC+ MAX11801GTC/V+ MAX11801EWC+T MAX11802ETC MAX11802EWC+T MAX11803ETC MAX11803EWC+T TEMP RANGE -40°C to +85°C -40°C to +105°C -40°C to +85°C -40°C to +85°C -40°C to +105°C -40°C to +85°C -40°C to +85°C -40°C to +85°C -40°C to +85°C -40°C to +85°C PIN-PACKAGE 12 TQFN-EP* 12 TQFN-EP* 12 WLP 12 TQFN-EP* 12 TQFN-EP* 12 WLP 12 TQFN-EP* 12 WLP 12 TQFN-EP* 12 WLP Applications Mobile Communication Devices PDAs, GPS Receivers, Personal Navigation Devices, Media Players Portable Instruments Typical Operating Circuits and Pin Configurations appear at end of data sheet. SPI is a trademark of Motorola, Inc. †Patents pending. POS Terminals Handheld Games Automotive Center Consoles *EP = Exposed pad. +Denotes a lead(Pb)-free/RoHS-compliant package. /V denotes an automotive qualified part. 1 ________________________________________________________________ Maxim Integrated Products For pricing, delivery, and ordering information, please contact Maxim Direct at 1-888-629-4642, or visit Maxim’s website at www.maxim-ic.com. Low-Power, Ultra-Small Resistive Touch-Screen Controllers with I2C/SPI Interface MAX11800–MAX11803 TABLE OF CONTENTS Absolute Maximum Ratings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8 Electrical Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8 I2C Timing Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .9 SPI Timing Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .10 Typical Operating Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .12 Pin Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .14 Functional Diagrams . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .15 Detailed Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .16 Position Measurements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .16 Pressure Measurements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .19 Touch-Detect Modes and Options . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .20 PUR and PUF . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .21 Idle Modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .21 Features Common to the MAX11800–MAX11803 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .21 Averaging Modes and Options . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .21 Combined Commands . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .23 Data Tagging . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .23 Low-Power Modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .23 Panel Setup, Measurement, and Scan Commands . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .24 Direct Conversion Mode Operations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .24 Interrupt Modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .24 Panel Setup Commands . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .27 Panel Measurement Commands . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .27 Combined Commands . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .28 Auxiliary Measurement Command . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .28 Autonomous Conversion Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .31 Measurement Operations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .32 Combined Commands . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .32 Delayed Touch Detection During Mode Transitions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .33 FIFO Memory . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .33 Clearing FIFO . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .33 FIFO Data Block Readback Structure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .33 FIFO Data Word Structure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .34 Block Readback Operations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .34 Clearing Interrupt . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .34 Aperture Modes* and Options . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .34 Aperture Range Requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .34 FIFO Aperture Criteria . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .35 2 _______________________________________________________________________________________ Low-Power, Ultra-Small Resistive Touch-Screen Controllers with I2C/SPI Interface MAX11800–MAX11803 TABLE OF CONTENTS (continued) Applications Information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .35 Using Aperture Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .35 Examples of Using Aperture Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .36 SPI Communication Sequence (MAX11800/MAX11802) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .38 SPI Configuration Register Write (MAX11800/MAX11802) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .38 SPI Configuration or Result Register Read (MAX11800/MAX11802) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .39 SPI Conversion Command (MAX11800/MAX11802) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .40 I2C-Supported Sequence (MAX11801/MAX11803) . . . . . . . . . . . . . . . . . . . I2C Configuration Register Write (MAX11801/MAX11803) . . . . . . . . . . . I2C Configuration or Result Register Read (MAX11801/MAX11803) . . . I2C Conversion Command (MAX11801/MAX11803) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .40 . . . . . . . . . . . . . . . . . . . . . . . . . . . . .40 . . . . . . . . . . . . . . . . . . . . . . . . . . . . .41 . . . . . . . . . . . . . . . . . . . . . . . . . . . . .42 Command and Register Map . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .42 User-Accessible Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .42 Status and Configuration Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .43 Data Readback Commands . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .44 Autonomous Conversion Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .44 Direct Conversion Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .44 Panel Setup and Measurement Commands . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .46 User Configuration Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .47 General Status Register (0x00) (Read Only) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .47 General Configuration Register (0x01) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .48 Measurement Resolution Configuration Register (0x02) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .48 Measurement Averaging Configuration Register (0x03) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .49 ADC Sampling Time Configuration Register (0x04) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .49 Panel Setup Timing Configuration Register (0x05) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .50 Delayed Conversion Configuration Register (0x06) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .50 Touch-Detect Pullup Timing Configuration Register (0x07) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .51 Autonomous Mode Timing Configuration Register (0x08) (MAX11800/MAX11801) . . . . . . . . . . . . . . . . . . . . . . . .51 Aperture Configuration Register (0x09) (MAX11800/MAX11801) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .52 Auxiliary Measurement Configuration Register (0x0A) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .53 Operating Mode Configuration Register (0x0B) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .54 MAX11800/MAX11802 Typical Operating Circuit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .55 MAX11801/MAX11803 Typical Operating Circuit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .55 Pin Configurations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .56 Chip Information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .56 Package Information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .56 Revision History . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .57 _______________________________________________________________________________________ 3 Low-Power, Ultra-Small Resistive Touch-Screen Controllers with I2C/SPI Interface MAX11800–MAX11803 LIST OF FIGURES Figure 1. I2C Timing Diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .10 Figure 2. SPI Timing Diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11 Figure 3a. MAX11800/MAX11801 Operation Modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .17 Figure 3b. MAX11802/MAX11803 Operation Modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .18 Figure 4. Position Measurements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .19 Figure 5. Pressure Measurements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .19 Figure 6. Touch-Detection Circuitry . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .21 Figure 7. Touch-Detection Operations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .22 Figure 8. State Machine Transitions (Direct Conversion Mode) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .24 Figure 9. Continuous Interrupt Mode (Direct Conversion Mode) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .25 Figure 10. Edge Interrupt Mode (Direct Conversion Mode) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .26 Figure 11. Command and Measurement Flow (DCM) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .27 Figure 12. Panel Setup and Measurement Commands . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .29 Figure 13. Combined Commands . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .30 Figure 14. State Machine Transitions––Autonomous Conversion Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .31 Figure 15. Clear-on-Read Interrupt Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .32 Figure 16. Aperture Usage Example Waveforms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .36 Figure 17. SPI Single Configuration Register Write Sequence . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .38 Figure 18. SPI Multiple Configuration Register Write Sequence . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .38 Figure 19. SPI Single-Byte Register Read Sequence . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .39 Figure 20. SPI Multiple-Byte Register Read Sequence . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .40 Figure 21. SPI Conversion Command . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .40 Figure 22. I2C Single Register Write Sequence . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .40 Figure 23. I2C Multiple Register Write Sequence . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .40 Figure 24. I2C Multiple Register Read Sequence . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .41 Figure 25. I2C Streamlined Register Read Sequence . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .41 Figure 26. I2C Conversion Command . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .42 4 _______________________________________________________________________________________ Low-Power, Ultra-Small Resistive Touch-Screen Controllers with I2C/SPI Interface MAX11800–MAX11803 LIST OF TABLES Table 1. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6 Table 2. Operating Modes, Conditions, and Options . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .19 Table 3. Summary of Physical Panel Settings for Supported Measurement Types . . . . . . . . . . . . . . . . . . . . . . . . . . .20 Table 4. Median Averaging Operations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .23 Table 5. Data Word Structure (All Direct Conversion Modes) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .23 Table 6. Measurement and Event Tags (Continuous Interrupt Mode) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .25 Table 7. Measurement and Event Tags (Edge Interrupt Mode) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .26 Table 8. Panel Setup Command Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .27 Table 9. Panel Measurement Command Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .28 Table 10. FIFO Data Block Structure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .33 Table 11. FIFO Data Word Structure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .34 Table 12. FIFO Data Measurement Tags . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .34 Table 13. FIFO Event Tags . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .34 Table 14. Readback and FIFO Contents with Aperture Mode Enabled . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .37 Table 15. Readback and FIFO Contents with Aperture Mode Disabled . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .37 Table 16. SPI Command and Data Format: 8 Bits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .43 Table 17. I2C Command and Data Format: 8 Bits Plus ACK . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .43 Table 18. Status and Configuration Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .44 Table 19. FIFO Data Readback Command (Autonomous Mode Only––MAX11800/MAX11801) . . . . . . . . . . . . . . . .45 Table 20. Data Readback Commands (Direct Mode Only) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .45 Table 21. I2C Readback Register Settings Following Conversion Commands . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .45 Table 22. Measurement Commands . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .46 _______________________________________________________________________________________ 5 Low-Power, Ultra-Small Resistive Touch-Screen Controllers with I2C/SPI Interface MAX11800–MAX11803 Table 1. Terminology TERM Panel, Touch Screen, Touch Panel TSC X+ XY+ YRTOUCH Z1 Z2 AUX ADC AP A VG MAF SAF TDM DEFINITION Resistive Touch Sensor: Panel, or touch screen, or touch panel are used interchangeably to denote the resistive touch sensor. Touch-Screen Controller: Devices attached to a touch screen that provide the interface between an application processor (AP) and touch screen. X Position Positive I/O: Analog I/O from resistive touch screen. See Figure 4 for configuration and measurement details. X Position Negative I/O: Analog I/O from resistive touch screen. See Figure 4 for configuration and measurement details. Y Position Positive I/O: Analog I/O from resistive touch screen. See Figure 4 for configuration and measurement details. Y Position Negative I/O: Analog I/O from resistive touch screen. See Figure 4 for configuration and measurement details. Touch Resistance: Represents the resistance between the X and Y planes of a resistive touch screen during a touch event. Z1 Measurement: A resistive touch-screen measurement to determine the resistance between the two planes within the panel sensor during a touch event (RTOUCH). See Figure 5 for configuration and measurement details. Z2 Measurement: A resistive touch-screen measurement to determine the resistance between the two planes within the panel sensor during a touch event (RTOUCH). See Figure 5 for configuration and measurement details. Auxiliary Input: Analog input to the MAX11800–MAX11803 that can be used to monitor external conditions such as battery voltage or temperature. Analog-to-Digital Converter: Circuit used to transform analog information into a form suitable for digital operations. Application Processor: An external microcontroller or microprocessor that interfaces to and controls the general operation of the MAX11800–MAX11803. Averaging Mode: The ability to average consecutive measurement results to reduce noise from switch bounce, power-supply ripple, and incomplete settling. Median Averaging Filter: The MAF first removes the minimum and maximum samples before taking the average of the remaining sample set. Straight Averaging Filter: The SAF takes the average of an entire sample set. Touch-Detect Mode: An untimed mode that monitors the panel for a touch using a user-selectable panel pullup resistor of either 50k or 100k . Direct Conversion Mode: A mode of operation in which the AP requests individual panel setup and conversion operations or automated combinations of measurements (X and Y, X and Y and Z1, or X and Y and Z1 and Z2). The AP maintains control over the initiation of panel setup, measurements, and the sampling f Autonomous Conversion Mode: A mode of operation in which the MAX11800/MAX11801 idle in TDM until a touch event occurs. After a touch is detected, the MAX11800/MAX11801 begin an automated sequence of measurements determined by the user configuration registers. Panel Setup Command: U ser-programmable modes for the purpose of allowing the panel sufficient time to settle, prior to the start of measurements. PSU commands configure the on-chip multiplexer in preparation to perform either X, Y, Z1, or Z2 measurements. Durations can either be specified and managed by the MAX11800–MAX11803 (in ACM and DCM) or managed by the AP (in DCM). Panel Measurement Command: Individual measurements of X or Y position and Z1 or Z2 pressure measurements. Combined Measurement Command: Combinations of PMCs (X and Y, X and Y and Z1, or X and Y and Z1 and Z2) offered by the MAX11800–MAX11803 and executed in series to reduce AP bus and interrupt activity. DCM ACM P SU PMC CMC 6 _______________________________________________________________________________________ Low-Power, Ultra-Small Resistive Touch-Screen Controllers with I2C/SPI Interface MAX11800–MAX11803 Table 1. Terminology (continued) TERM FIFO DEFINITION First-In First-Out Memory: The MAX11800–MAX11803 contain a 1024-bit FIFO that is used to store conversion results when operating in autonomous conversion mode. FIFO depth indicates the number of words (16-bit quantity) in the FIFO. Scan: Generally, a single sequence of operations performed in DCM or ACM. The operations could include a panel setup operation, followed by a panel measurement operation, or a combined measurement operation. Scan Block: Generally, a sequence of multiple operations performed in DCM or ACM. The operations could include panel-setup operations, panel-measurement operations, or combined measurement operations. Timed Scan: A scan or scan block operation that uses the on-chip oscillator and timer. The timer is controlled through the configuration registers and represents an array of fixed (time) quantities that are user selectable (MAX11800/MAX11801). Data Tag: Information appended to the end of an ADC conversion result. Tags indicate the type of measurement and touch status associated with each panel observation. See the definitions for ETAG and MTAG (also in Table 1). Event Tag: Data tags indicating the panel touch status observed during a measurement. Measurement Tag: Data tag indicating the type of measurement read back by the AP (either X, Y, Z1, or Z2). Touch Interrupt Request: Active-low interrupt, indicating that a touch is present (CINT) or has been initiated (EINT) in DCM, or that new data is available in the FIFO in ACM. Edge Interrupt Mode: Indicates, through TIRQ, that a touch has been initiated (EINT) in DCM. The duration that TIRQ is low is user programmable. Continuous Interrupt Mode: Indicates, through TIRQ, that a touch is present (CINT) in DCM. TIRQ goes low to indicate the presence of a touch and stays low until the touch event ceases. Clear-on-Read Interrupt Mode: Used in ACM only. TIRQ goes low to indicate the presence of new FIFO data. The interrupt is cleared when the data is read by the AP (MAX11800/MAX11801). Aperture Mode: Available in ACM only. Reduces data writes to the FIFO by spatially filtering measurement data. Continuous Bit: An option in DCM to return the MAX11800–MAX11803 to a panel setup (wait) mode (PSU) after a conversion, rather than a return to TDM (recommended only for applications with very long panel settling times and request controlling their own averaging). The continuous bit resides in bit 0 (R0) of the PSU and PMC registers. Low-Power Mode: An idle mode used in DCM/EINT or ACM modes, when a touch is detected at the conclusion of the last measurement. This indicates a new measurement needs to be requested or scheduled (the touch-detect pullup is not engaged to save power). Pullup Rough: A fast pullup mode, which uses the main X+ switch in parallel with the on-chip resistive pullup (50kΩ/100kΩ) to quickly slew the touch panel capacitances. RPUR ≤ 10Ω typical. Pullup Fine: A slow (fine) pullup mode, which uses the on-chip resistive pullup to slew the touch-panel capacitances to their final values (RPUF = 50kΩ or 100kΩ) typical and is required for all applications. Successive Approximation Register ADC: An analog-to-digital converter that converts a continuous analog waveform into a discrete digital representation through a binary search through all possible quantization levels before finally converging upon a digital output for each conversion. Inter-Integrated Circuit: A multimaster serial computer bus that is used to attach low-speed peripherals to other components using two bidirectional open-drain lines, serial data (SDA) and serial clock (SCL), pulled up with resistors. Serial Peripheral Interface: A serial interface in which a master device supplies clock pulses to exchange data serially with a slave over two data wires (master-slave and slave-master). Scan Scan Block Timed Scan Untimed Scan Untimed Scan: A scan or scan block operation that is controlled by the AP. This only applies to DCM. TAG ETAG MTAG TIRQ EINT CINT CORINT APER CONT LPM PUR PUF SAR ADC I2C SPI _______________________________________________________________________________________ 7 Low-Power, Ultra-Small Resistive Touch-Screen Controllers with I2C/SPI Interface MAX11800–MAX11803 ABSOLUTE MAXIMUM RATINGS VDD to GND ...........................................................-0.3V to +4.0V X+, X-, Y+, Y-, AUX, TIRQ to GND ........................-0.3V to +4.0V SCL, CLK, SDA, DIN, A0, CS, A1, DOUT to GND.-0.3V to +4.0V Maximum Current into Any Pin .........................................±50mA Continuous Power Dissipation (TA = +70°C) 12-Pin TQFN (derate 24.4mW/°C above +70°C) ....1951.2mW 12-Pin WLP (derate 6.5mW/°C above +70°C) ..........518.8mW Operating Temperature Ranges MAX1180_E_ _..................................................-40°C to +85°C MAX1180_G_ _ ...............................................-40°C to +105°C Storage Temperature Range .............................-65°C to +150°C Junction Temperature ......................................................+150°C Soldering Temperature (reflow) .......................................+260°C Lead Temperature (soldering, 10s) .................................+300°C Note 1: All WLP devices are 100% production tested at TA = +25°C. Specifications over temperature limits are guaranteed by design and characterization. Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and functional operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability. ELECTRICAL CHARACTERISTICS (VDD = 1.7V to 3.6V, TA = -40°C to +85°C (MAX11800E–MAX11803E), TA = -40°C to +105°C (MAX11800G/MAX11801G), unless otherwise noted. Typical values are at TA = +25°C and VDD = 3.3V, unless otherwise noted.) PARAMETER ADC ADC Resolution Differential Nonlinearity Integral Nonlinearity Offset Error Gain Error Throughput TOUCH SENSORS (X+, X-, Y+, Y-, AUX) Switch On-Resistance Switch Driver Current Input Voltage Range POWER SUPPLY (VDD) Supply Voltage 0 VDD Power-down mode. All digital inputs static. TDM. All digital inputs static. Does not include panel currents when touched. Supply Current Timed LPM. All digital inputs static. Does not include panel currents when touched. AUX conversions at 34.4ksps equivalent rate, SPI AUX conversions at 34.4ksps equivalent rate, I2C AUX conversions at 34.4ksps equivalent rate, SPI AUX conversions at 34.4ksps equivalent rate, I2C 1.7V 3.6V 3.6V 1.7V 3.3V 1.7V 3.3V 1.7V 3.3V 1.7V 3.3V 1.7V 3.3V 9 16 216 273 202 269 367 901 343 888 1.7 VDD = 1.7V VDD = 3.3V 7 5 12 10 50 VDD 3.6 1 2 7 20 40 400 550 400 550 μA Ω mA V V 105 DNL INL No missing codes 12-bit resolution 12-bit resolution 10 11 ±1.5 ±1.5 ±2 ±4 Bits LSB LSB LSB LSB ksps SYMBOL CONDITIONS MIN TYP MAX UNITS Power Consumption μW 8 _______________________________________________________________________________________ Low-Power, Ultra-Small Resistive Touch-Screen Controllers with I2C/SPI Interface ELECTRICAL CHARACTERISTICS (continued) (VDD = 1.7V to 3.6V, TA = -40°C to +85°C (MAX11800E–MAX11803E), TA = -40°C to +105°C (MAX11800G/MAX11801G), unless otherwise noted. Typical values are at TA = +25°C and VDD = 3.3V, unless otherwise noted.) PARAMETER SYMBOL CONDITIONS MIN 0.7 x VDD 0.3 x VDD VIN = 0V or VDD -1 0.5 x VDD 6 0.9 x VDD 0.9 x VDD 0.4 0.4 125 +1 TYP MAX UNITS DIGITAL INPUTS (SDA, DIN, SCL, CLK, A0, CS, A1) Input Logic-High Voltage Input Logic-Low Voltage Input Leakage Current Input Hysteresis Input Capacitance DIGITAL OUTPUTS (SDA, DOUT, TIRQ) DOUT, ISOURCE = 1mA Output Logic-High VOH TIRQ, CMOS configuration, ISOURCE = 1mA Output Logic-Low—TIRQ, DOUT Output Logic-Low—SDA TIRQ Pullup Resistor VOL VOL ISINK = 1mA ISINK = 3mA VIH VIL IIN VHYS V V μA V pF MAX11800–MAX11803 V V V kΩ I2C TIMING CHARACTERISTICS (VDD = 1.7V to 3.6V, TA = -40°C to +85°C (MAX11801E and MAX11803E), TA = -40°C to +105°C (MAX11801G), unless otherwise noted. Typical values are at TA = +25°C and VDD = 3.3V, unless otherwise noted. See Figure 1.) PARAMETER Serial-Clock Frequency Bus Free Time Hold Time for START Condition SCL Pulse-Width Low SCL Pulse-Width High Setup Time for Repeated START (Sr) Condition Data Hold Time Data Setup Time SDA and SCL Rise/Fall Time SDA and SCL Fall Time Setup Time for STOP Condition Bus Capacitance Allowed Pulse Width of Suppressed Spike SYMBOL fSCL tBUF tHD;STA tLOW tHIGH tSU;STA tHD;DAT tSU;DAT tR, tF tTF tSU;STO CB tSP VDD = 1.7V to 2.7V VDD = 2.7V to 3.6V Receiving Transmitting Bus free time between STOP and START condition After this period, the first clock pulse is generated CONDITIONS MIN 0 1.3 0.6 1.3 0.6 0.6 0 100 20 + CB/10 20 + CB/10 0.6 10 10 100 400 50 300 250 900 TYP MAX 400 UNITS kHz μs μs μs μs μs ns ns ns ns μs pF ns _______________________________________________________________________________________ 9 Low-Power, Ultra-Small Resistive Touch-Screen Controllers with I2C/SPI Interface MAX11800–MAX11803 SPI TIMING CHARACTERISTICS (VDD = 1.7V to 3.6V, TA = -40°C to +85°C (MAX11800E and MAX11802E), TA = -40°C to +105°C (MAX11800G), unless otherwise noted. Typical values are at TA = +25°C and VDD = 3.3V, unless otherwise noted. See Figure 2.) PARAMETER CLK Frequency CLK Period CLK Pulse-Width High CLK Pulse-Width Low CS Low to 1st CLK Rise Setup CS Low After 0th CLK Rise Hold SYMBOL fCLK tCP tCH tCL tCSS0 tCSH0 To prevent a 0th CLK read from being taken as a 1st read in a free-running application To prevent a 17th CLK read from being recognized by the device in a free-running application 40 18 18 18 0 CONDITIONS MIN TYP MAX 25 UNITS MHz ns ns ns ns ns CS High to 17th CLK Setup CS High After 16th CLK Falling Edge Hold CS Pulse-Width High DIN to CLK Setup DIN Hold After CLK DOUT Transition Valid After CLK Rise DOUT Remains Valid After CLK Rise DOUT Valid Before CLK Rise CS Rise to DOUT Disable CLK Rise to DOUT Enable tCSS1 18 ns tCSH1 tCSW tDS tDH tDOT tDOH tDO1 tDOD tDOE Output transition time Output hold time tDO1 = tCP - tDOT CLOAD = 20pF CLOAD = 20pF. Minimum = hold time with regard to 8th CLK read. Maximum = transition time with regard to 8th CLK read. 0 18 25 0 25 3 10 40 3 25 ns ns ns ns ns ns ns ns ns tF SDA tBUF tR tLOW tSU;DAT tHIGH tHD;STA S tSU;STO Sr P S tSP tHD;STA SCL tHD;DAT tF tSU;STA Figure 1. I2C Timing Diagram 10 ______________________________________________________________________________________ Low-Power, Ultra-Small Resistive Touch-Screen Controllers with I2C/SPI Interface MAX11800–MAX11803 tDS tCSH0 tCSS0 CS tCL tCSS1 CLK 0 1 8 9 16 tDH tCH tCP tSCH1 tCSW DIN X HIGH-Z A6 A5 A4 A3 A2 A1 A0 W D7 D6 D5 D4 D3 D2 D1 D0 DOUT SPI WRITE OPERATION tDS tCSS0 CS tDH tCH tCL tDOE tDO1 tCP tDOH tDO0 CLK 1 8 9 16 DIN X HIGH-Z A6 A5 A4 A3 A2 A1 A0 R X X X X X X X X HIGH-Z DOUT D7 D6 D5 D4 D3 D2 D1 D0 SPI READ OPERATION Figure 2. SPI Timing Diagram ______________________________________________________________________________________ 11 Low-Power, Ultra-Small Resistive Touch-Screen Controllers with I2C/SPI Interface MAX11800–MAX11803 Typical Operating Characteristics (VDD = 1.8V at TA = -40°C to +85°C (TA = -40°C, TA = 0°C, TA = +25°C, and TA = +85°C), 12-bit mode, all measurements using noncontinuous AUX input. SPI = 10MHz and I2C = 400kHz, unless otherwise noted. Resistive touch-screen panel (X+ to X- = 608Ω, Y+ to Y- = 371Ω).) AVERAGE SUPPLY CURRENT vs. SAMPLING RATE 80 SUPPLY CURRENT (FA) 70 60 50 40 30 20 10 0 0 DATA TAKEN WITH RESISTIVE TOUCH SENSOR cps = COORDINATES PER SECOND AUTONOMOUS MODE MAX11800 toc01 AVERAGE SUPPLY CURRENT vs. SAMPLING RATE MAX11800 toc02 AVERAGE SUPPLY CURRENT vs. SAMPLING RATE DIRECT EDGE INTERRUPT MODE MAX11800 toc03 90 5 4 SUPPLY CURRENT (FA) 3 2 1 cps = COORDINATES PER SECOND 0 0 DIRECT CONTINUOUS INTERRUPT MODE 5 4 SUPPLY CURRENT (FA) 3 2 1 0 cps = COORDINATES PER SECOND 0 20 40 60 80 100 120 140 160 180 200 SAMPLING RATE (cps) 20 40 60 80 100 120 140 160 180 200 SAMPLING RATE (cps) 20 40 60 80 100 120 140 160 180 200 SAMPLING RATE (cps) SUPPLY CURRENT IN POWER-DOWN vs. TEMPERATURE MAX11800 toc04 SWITCH RESISTANCE vs. SUPPLY VOLTAGE MAX11800 toc05 SWITCH RESISTANCE vs. TEMPERATURE Y+ MAX11800 toc06 0.40 POWER-DOWN SUPPLY CURRENT (µA) 0.36 0.32 0.28 0.24 0.20 0.16 0.12 0.08 0.04 0 -40 -15 10 35 60 8 7 6 5 4 3 X+ Y+ 7 6 5 RON (I) 4 3 X- X+ Y- RON (I) Y- X- 2 1 85 1.6 2.0 2.4 2.8 3.2 3.6 -40 -15 10 35 60 85 TEMPERATURE (NC) VDD (V) TEMPERATURE (NC) CHANGE IN ADC GAIN vs. TEMPERATURE MAX11800 toc07 CHANGE IN ADC OFFSET vs. TEMPERATURE 3 DELTA FROM +25NC (LSB) 2 1 0 -1 -2 -3 MAX11800 toc08 4 3 DELTA FROM +25NC (LSB) 2 1 0 -1 -2 -3 -4 -40 -10 20 50 80 4 110 -4 -40 -10 20 50 80 110 TEMPERATURE (NC) TEMPERATURE (NC) 12 ______________________________________________________________________________________ Low-Power, Ultra-Small Resistive Touch-Screen Controllers with I2C/SPI Interface Typical Operating Characteristics (continued) (VDD = 1.8V at TA = -40°C to +85°C (TA = -40°C, TA = 0°C, TA = +25°C, and TA = +85°C), 12-bit mode, all measurements using noncontinuous AUX input. SPI = 10MHz and I2C = 400kHz, unless otherwise noted. Resistive touch-screen panel (X+ to X- = 608Ω, Y+ to Y- = 371Ω).) AVERAGE SUPPLY CURRENT INTERNAL OSCILLATOR CLOCK AVERAGE SUPPLY CURRENT vs. SAMPLING RATE FREQUENCY vs. TEMPERATURE vs. SAMPLING RATE INTERNAL OSCILLATOR CLOCK FREQUENCY (MHz) MAX11800 toc09 MAX11800 toc10 MAX11800–MAX11803 2.5 SUPPLY CURRENT (FA) 2.0 1.5 1.0 0.5 DIRECT CONVERSION MODE—AUXILIARY INPUT 100 SUPPLY CURRENT (FA) 80 60 40 20 AUXILIARY INPUT DATA SAMPLED AT 1ksps AND 2ksps WITH EIGHT AND 16 SAMPLES AVERAGING ENABLED 2.06 2.04 2.02 2.00 1.98 1.96 1.94 1.92 1.90 -40 -15 10 VDD = 1.8V VDD = 3.0V VDD = 3.6V sps = SAMPLES PER SECOND 0 0 20 40 60 80 100 120 140 160 180 200 SAMPLING RATE (sps) 0 8 ksps = KILO-SAMPLES PER SECOND 16 24 32 35 60 85 EQUIVALENT SAMPLING RATE (ksps) TEMPERATURE (NC) INTERNAL OSCILLATOR CLOCK FREQUENCY vs. SUPPLY VOLTAGE INTERNAL OSCILLATOR CLOCK FREQUENCY (MHz) MAX11800 toc12 POWER CONSUMPTION vs. SAMPLE RATE 140 POWER CONSUMPTION (FW) 120 100 80 60 40 20 DIRECT EDGE MODE 0 50 100 SAMPLE RATE (cps) 150 200 DIRECT CONTINUOUS MODE cps = COORDINATES PER SECOND DATA TAKEN WITH RESISTIVE TOUCH SENSOR AUTONOMOUS MODE MAX11800 toc13 2.08 2.06 2.04 2.02 2.00 1.98 1.96 1.94 1.92 1.90 1.8 2.4 VDD (V) 3.0 160 3.6 0 ______________________________________________________________________________________ 13 MAX11800 toc11 3.0 120 2.08 Low-Power, Ultra-Small Resistive Touch-Screen Controllers with I2C/SPI Interface MAX11800–MAX11803 Pin Description PIN MAX11800/MAX11802 TQFN 1 2 3 4 5 6 7 8 9 10 11 12 — — — — EP WLP A4 B4 B3 C4 C3 C2 C1 B1 A1 B2 A2 A3 — — — — — MAX11801/MAX11803 TQFN 1 2 3 4 5 6 — — — — 11 12 7 8 9 10 EP WLP A4 B4 B3 C4 C3 C2 —— — — A2 A3 C1 B1 A1 B2 — X+ VDD GND XYTIRQ DIN CLK CS DOUT AUX Y+ SDA SCL A0 A1 EP X+ Channel Input/Output Power Supply. Bypass VDD to GND with a 1μF capacitor. Ground X- Channel Input/Output Y- Channel Input/Output Active-Low Touch Interrupt Output SPI Serial Data Input SPI Serial Data Clock Input SPI Chip-Select Input SPI Data Output Auxiliary Input Y+ Channel Input/Output I2C Serial Data Bus Input/Output I2C Serial Data Clock Input I2C Address Input Bit 0 I2C Address Input Bit 1 Exposed Pad. Connected to ground. NAME FUNCTION 14 ______________________________________________________________________________________ Low-Power, Ultra-Small Resistive Touch-Screen Controllers with I2C/SPI Interface Functional Diagrams MAX11800–MAX11803 MAX11800/MAX11801 POWER AND BIAS VDD AUX DOUT (A1) X+ XY+ YTOUCHSCREEN INTERFACE MUX SAR ADC LOGIC CORE SERIAL INTERFACE PHYSICAL LAYER (ANALOG INTERFACE) SIF PHY AUTONOMOUS MODE ENGINE V DD INTERNAL CLOCK INTERRUPT GENERATION ENGINE GND FIFO TIRQ CS (A0) CLK (SCL) DIN (SDA) MAX11802/MAX11803 POWER AND BIAS VDD AUX DOUT (A1) X+ XY+ YTOUCHSCREEN INTERFACE MUX SAR ADC LOGIC CORE SERIAL INTERFACE PHYSICAL LAYER (ANALOG INTERFACE) SIF PHY CS (A0) CLK (SCL) V DD INTERNAL CLOCK INTERRUPT GENERATION ENGINE GND DIN (SDA) TIRQ ______________________________________________________________________________________ 15 Low-Power, Ultra-Small Resistive Touch-Screen Controllers with I2C/SPI Interface MAX11800–MAX11803 Detailed Description The MAX11800–MAX11803 contain standard features found in a typical resistive touch-screen controller as well as advanced features. Standard features included in the MAX11800–MAX11803 are: • 4-wire touch-screen interface • X/Y coordinate measurement • Touch pressure measurement • Direct conversion operation—requires direct AP involvement • Single commands—AP initiates all activity one command at a time • Ratiometric measurement • 12-bit SAR ADC • Single 1.8V to 3.3V supply • Programmable touch-detect pullup—50k Ω or 100kΩ • Auto power-down control for low-power operation • 400kHz I2C interface (MAX11801/MAX11803) Advanced features found in the MAX11800–MAX11803 include: • Autonomous conversion operation—minimal AP involvement (MAX11800/MAX11801) • On-chip FIFO—buffers up to 16 consecutive measurements (MAX11800/MAX11801) • Data tagging—records measurement and touchevent information • Filtering—reduces noise using straight or median averaging • Aperture mode—provides spatial filtering (MAX11800/MAX11801) • Combined commands—multiple operations performed with a single AP command • Digital processing to reduce serial bus activity • Digital processing to reduce interrupt generation • User-programmable acquisition modes • Programmable interrupt output drive • 25MHz SPI interface (MAX11800/MAX11802) The MAX11800–MAX11803 operate in one of two toplevel modes: direct conversion mode (DCM) or autonomous conversion mode (ACM). Direct conversion mode requires the AP to initiate all activity to and from the MAX11800–MAX11803. DCM is the operating mode that most standard resistive touch-screen controllers use. ACM allows the MAX11800/MAX11801 to perform measurements automatically and inform the AP when they are complete, reducing data transfers on the serial bus as well as generating fewer interrupt requests. The MAX11800/MAX11801 can operate in the standard mode that is familiar to users, or in the advanced features mode to provide additional flexibility. Both DCM and ACM support averaging, data tagging, and combined commands. Certain commands and operations are only available in DCM, while others are only available in ACM. See Figures 3a and 3b and Table 2 for details. Position Measurements Position measurements determine either the X or Y coordinates of the point of contact on the panel sensor. Allow adequate time for the panel to settle when switching between X and Y measurements. Figure 4 shows the physical setup of the panel when performing position measurements. The element RTOUCH represents the resistance between the X and Y planes of the panel sensor. RTOUCH does not contribute to the error when performing position measurements. R TOUCH a ffects the panel settling time required between each valid measurement. The panel end-to-end resistance in the direction of measurement determines the power applied across the panel. The panel dissipates power in the X elements when performing an X direction measurement and dissipates power in the Y elements when performing a Y direction measurement. 16 ______________________________________________________________________________________ Low-Power, Ultra-Small Resistive Touch-Screen Controllers with I2C/SPI Interface MAX11800–MAX11803 MAX11800 MAX11801 SETUP REGISTERS REGISTER 0x0B DIRECT CONVERSION (DCM) OPERATION MODES OPERATION MODE AUTONOMOUS CONVERSION (ACM) SETUP REGISTERS REGISTER 0x0B REGISTER 0x05 REGISTER 0x6x REGISTER 0x7x REGISTER 0x7x REGISTER 0x0A PANEL SETUP COMMANDS (PSU) PANEL MEASUREMENT COMMANDS (PMC) PANEL COMBINED COMMANDS (CMC) AUX MEASUREMENT COMMANDS (AMC) COMMANDS PANEL SETUP COMMANDS (PSU) PANEL MEASUREMENT COMMANDS (PMC) PANEL COMBINED COMMANDS (CMC) N/A REGISTER 0x05 REGISTER 0x6x* REGISTER 0x7x* REGISTER 0x7x* REGISTER 0x0B REGISTER 0x03 REGISTER 0x0B X, Y, Z1, Z2 MEASUREMENTS AVERAGING MEASUREMENTS MEASUREMENT TYPES X, Y, Z1, Z2 MEASUREMENTS AVERAGING MEASUREMENTS REGISTER 0x0B REGISTER 0x03 REGISTER 0x0B REGISTER 0x01 REGISTER 0x01 EDGE INTERRUPT MODE (EINT) CONTINUOUS INTERRUPT MODE (CINT) N/A INTERRUPT TYPES N/A N/A CLEAR-ON-READ INTERRUPT (CORINT) EVENT TAG (ETAG) (IF CONT = 1, NO FIFO) MEASUREMENT TAG (MTAG) (IF CONT = 1, NO FIFO) DATA TAGGING TYPES EVENT TAG (ETAG) (USES FIFO) MEASUREMENT TAG (MTAG) (USES FIFO) N/A APERTURE APERTURE SETTINGS REGISTER 0x09 REGISTER 0x01 TIRQ CONFIGURATION TIRQ TIRQ CONFIGURATION REGISTER 0x01 REGISTER 0x02 REGISTER 0x04 REGISTER 0x06 ADC RESOLUTION AND TIMING ADC ADC RESOLUTION AND TIMING REGISTER 0x02 REGISTER 0x04 REGISTER 0x06 REGISTER 0x07 PUR AND PUF TIMING TDM TIMING PUR AND PUF TIMING REGISTER 0x07 N/A AUTO TIMING TINIT AND SCANP TIMING REGISTER 0x08 *THESE REGISTERS CANNOT BE ALTERED WHEN AUTONOMOUS MODE IS ACTIVE. THEY SHOULD BE INITIALIZED BEFORE AUTONOMOUS MODE IS ACTIVATED. Figure 3a. MAX11800/MAX11801 Operation Modes ______________________________________________________________________________________ 17 Low-Power, Ultra-Small Resistive Touch-Screen Controllers with I2C/SPI Interface MAX11800–MAX11803 MAX11802 MAX11803 OPERATION MODES SETUP REGISTERS REGISTER 0x05 REGISTER 0x6x REGISTER 0x7x REGISTER 0x7x REGISTER 0x0A PANEL SETUP COMMANDS (PSU) PANEL MEASUREMENT COMMANDS (PMC) PANEL COMBINED COMMANDS (CMC) AUX MEASUREMENT COMMANDS (AMC) COMMANDS REGISTER 0x0B REGISTER 0x03 REGISTER 0x0B X, Y, Z1, Z2 MEASUREMENTS AVERAGING MEASUREMENTS MEASUREMENT TYPES REGISTER 0x01 REGISTER 0x01 EDGE INTERRUPT MODE (EINT) CONTINUOUS INTERRUPT MODE (CINT) INTERRUPT TYPES EVENT TAG (ETAG) MEASUREMENT TAG (MTAG) DATA TAGGING TYPES REGISTER 0x01 TIRQ CONFIGURATION TIRQ REGISTER 0x02 REGISTER 0x04 REGISTER 0x06 ADC RESOLUTION AND TIMING ADC REGISTER 0x07 PUR AND PUF TIMING TDM TIMING Figure 3b. MAX11802/MAX11803 Operation Modes 18 ______________________________________________________________________________________ Low-Power, Ultra-Small Resistive Touch-Screen Controllers with I2C/SPI Interface MAX11800–MAX11803 Table 2. Operating Modes, Conditions, and Options OPERATION PSU PMC CMC TDM LPM AVG MODE DCM MAX11800– MAX11803 ACM MAX11800/ MAX11801 AUX Yes Yes Yes Yes No Yes FIFO APER COR X, Y, PUR EINT CINT CONT MTAG ETAG INT Z1, Z2 PUF Yes Yes Yes 2 Yes 2 Yes Yes Yes No No No Yes 1 No Yes 1 Yes 1 Yes 3 No Yes No Yes — Yes Yes 3 Yes No Yes No Yes No No No Yes No Yes No Yes No No No No No Yes No 1In ACM, the choices are limited to X and Y scan, or X and Y and Z1 scan, or X and Y and Z1 and Z2 scan. 2In DCM, each ADC conversion is tagged with MTAG and ETAG only when the continuous bit is set (CONT = 1). DCM does not use the FIFO and, therefore, the AP should request the data at the end of the conversion cycle. 3A separate configuration register for delay time, sampling time, averaging, and ADC resolution settings configures the AUX input. Pressure Measurements Z1 and Z2 measurements determine the resistance between the two planes within the panel sensor during a touch (RTOUCH). Depending on the known physical properties of the panel, one of two equations extract the value of RTOUCH, providing information about the pressure and area of the touch applied to the panel. Allow adequate time for the panel to settle when switching between position and pressure measurements. Figure 5 shows the physical setup of the panel when performing pressure measurements. Z1 and Z2 measurements allow observation of the voltage on either side of the effective RTOUCH resistance. With both Z1 and Z2 measurements available, compute RTOUCH as follows: ⎛X ⎞ ⎛Z ⎞ RTOUCH = RXPLATE ⎜ POSITION ⎟ ⎜ 2 − 1⎟ ⎝ 2NBITX ⎠ ⎝ Z1 ⎠ If only a Z1 measurement is available, compute RTOUCH as follows: X ⎛R ⎞ RTOUCH = ⎜ XPLATE POSITION ⎟ ⎝ ⎠ 2NBITX Y ⎛ ⎞ ⎛ 2NBITZ ⎞ − 1⎟ − RYPLATE ⎜ 1 − POSITION ⎟ ⎜ ⎝ ⎝ Z1 ⎠ 2NBITY ⎠ The power applied across the panel during pressure measurements is greatly dependent on RTOUCH and the physical position of the touch. The maximum power dissipation in the panel during a pressure measurement is approximately PZ = VDD2/RTOUCH. This maximum power dissipation condition is observed when the point of contact is in the top left corner of the panel sensor. PANEL RTOUCH Y+ ADC INPUT PANEL RTOUCH Y+ VDD PANEL RTOUCH Y+ VDD PANEL RTOUCH Y+ VDD X- X+ Y- X- X+ ADC INPUT YXX+ ADC INPUT Z1 PRESSURE MEASUREMENT Y- X- X+ Y- ADC INPUT VDD X POSITION MEASUREMENT Y POSITION MEASUREMENT Z2 PRESSURE MEASUREMENT Figure 4. Position Measurements Figure 5. Pressure Measurements 19 ______________________________________________________________________________________ Low-Power, Ultra-Small Resistive Touch-Screen Controllers with I2C/SPI Interface MAX11800–MAX11803 The planar end-to-end resistance included in the current path is minimal at this location. Keep the averaging and panel settling durations to the minimum required by the application when pressure measurements are required. Table 3 summarizes the physical panel settings for supported measurement types. a touch is detected. The YMSW and TSW transistors are on, and the XPSW and PSW transistors are off. With no touch present, the Y- input of the TSC is at ground and the X+ input is at VDD - V TN, where VTN is the threshold voltage of the TSW nMOS device. This is a low-power mode in which no current is consumed until a panel touch occurs. When a touch is present on the panel, the touch-screen controller (TSC) X+ input is pulled low by the touch panel plate resistance and the YMSW transistor. This causes TOUCH to assume a logic high and the MAX11800–MAX11803 either issue the TIRQ interrupt for direct conversion modes or begin self-timed scans for autonomous conversion mode. The value of the user-defined R TD depends on the characteristics of the panel. To ensure reliable detection values, worst-case panel resistance must be checked against RTD. The interaction between RTD and the panel (or external noise rejecting) capacitance determines how quickly the panel can be switched from measurement modes back to touch monitoring mode without reporting false touches or erroneous tags due to panel settling. Panel touch status is also required to tag data from a completed scan and measurement operation. Following each scan operation, the panel must be returned to TDM to determine if the panel is still being touched and if the data obtained during the scan operation should be considered valid. This operation is required since the panel cannot be monitored for the presence of a touch during the scan and measurement procedure. The MAX11800–MAX11803 must return to TDM after completing a measurement and making a decision on the touch status of the panel. The measurement procedure is only completed upon resolution of the touch status and when data is tagged and available for Touch-Detect Modes and Options Figure 6 shows the internal circuitry in the MAX11800–MAX11803 used to detect the presence of a touch on the panel. The selection of the pullup resistance value (RTD = touch-detect resistance) and the durations of the rough pullup interval (PUR = lowimpedance pullup) and fine pullup interval (PUF = highimpedance pullup) are user-defined. The MAX11800–MAX11803 revert to the low-power panel setup when placed in touch-detect mode (TDM). Figure 6 shows the active panel drive switches (YMSW and XPSW are omitted for simplicity). TSW is a dedicated pullup switch used in TDM. TSW is also used during PUF and TDM. XPSW is activated during PUR periods. TDRSEL allows the selection of an internal pullup resistor value of either 50kΩ or 100kΩ. The X and Y touch-screen plates create an open circuit with no current flow in the panel when the panel is not being touched. In this case, TOUCH (see Figure 6) is low. When a touch causes contact between the panel X and Y plates, a current path is created and TOUCH is pulled high, as long as RPX + RPY (the sum of panel end-to-end resistance) is much lower than RTD. Typical open-circuit panel plate resistances range from 200Ω to 1000Ω. The MAX11800–MAX11803 enter high-impedance pullup mode (50kΩ or 100kΩ) when the panel is not being touched and the device is idle in this mode until Table 3. Summary of Physical Panel Settings for Supported Measurement Types MODE X Y Z1 Z2 PUR TDM or PUF LPM X+ VDD ADC_IN ADC_IN U VDD (10Ω) VDD through 50kΩ or 100kΩ U XGND U GND GND U U U Y+ ADC_IN VDD VDD VDD U U U YU GND U ADC_IN GND GND U REF+ X+ Y+ Y+ Y+ U U U REFXYXX— — — Note: The ADC input is fully differential with the negative input internally connected to GND. The MAX11800–MAX11803 control access to the PUR, PUF, TDM, and LPM, which do not require setup procedures. U indicates unconnected node. 20 ______________________________________________________________________________________ Low-Power, Ultra-Small Resistive Touch-Screen Controllers with I2C/SPI Interface readback. The characteristics of the return to TDM and the timing of the decision are configurable through the touch-detect pullup timing configuration register (0x07). Program the MAX11800–MAX11803 in the context of the application to maximize power efficiency and achieve the desired scan throughput. teristics and the desired scan throughput rates to minimize power dissipation. While use of the PUR mode is optional, the PUF period is required for all applications. The PUF interval allows the panel to resettle following scan or optional PUR intervals. When a touch is not present, the panel capacitance settles toward VDD through the internal pullup switch and a portion of the panel resistance (with the optional PUR mode disabled). When a touch is present, the panel capacitance settles toward ground through a portion of the panel resistance, ideally significantly lower than the selected pullup impedance, RTD. Allow enough recovery time for settling through the panel when using a PUR mode. Figure 7 illustrates the touchdetection operations. MAX11800–MAX11803 PUR and PUF PUR is a fast pullup mode, which uses the main X+ switch in parallel with the resistive pullup to quickly slew the panel capacitance. PUF uses only the touch-detect pullup resistor, RTD. PUR and PUF serve the same function as TDM, but are timed so that the panel can settle after completing measurements and before rendering any decisions on the touch status of the panel. Use the optional PUR mode to reduce the time to tag data by momentarily placing the panel in a low-impedance (< 10Ω) pullup mode instead of using the available 50kΩ/100kΩ touch-detection pullup resistors. This operation forces the monitored TSC input high during the PUR interval. Once the PUR interval expires, a PUF interval must be allowed so that the panel can recover and pull the TSC input low in case a touch is present. The purpose of the PUR mode is to reduce the time required to determine touch status by avoiding long pullup time constants caused by high-capacitance touch panels and the high-impedance on-chip pullup resistors (RTD). When a touch is present during PUR intervals, the current through the low-impedance pullup (XPSW) and panel combination is significantly higher than that observed in the PUF mode. The durations in the PUR mode must be matched to the panel charac- Idle Modes Once the PUF period expires, the preceding measurement data is tagged and made available for readback. The MAX11800–MAX11803 transition to an appropriate mode depending on the conversion and interrupt mode selected. Features Common to the MAX11800–MAX11803 Averaging Modes and Options The MAX11800–MAX11803 contain a programmable averaging filter. When enabled, this feature allows collecting 4, 8, or 16 consecutive samples for each measurement type requested. The number of the samples for each measurement type is controlled by configuration register 0x03. The AUX depth input is selected in configuration register 0x0A. Averaging can be assigned to each measurement type. For example, X and Y measurements can use an average of 16 samples, while Z measurements can use one or four samples to save power. The MAX11800–MAX11803 can be configured to perform one of two statistical operations. One option is a median averaging filter (MAF). The MAF first removes outliers before taking the average of the remaining sample set. The second is a straight averaging filter (SAF), which takes the average of the entire sample set. Averaging modes are supported in both direct and autonomous conversion modes. Both filter types and position/pressure averaging are controlled by configuration register 0x0B. This allows switching between direct and autonomous modes using a single configuration write through the serial interface (SIF). Table 4 presents the details of the median averaging operations of the MAX11800–MAX11803. VDD PSW TDRSEL RTD Y+ XPSW XX+ PUR TSW RTD TOUCH (TO MAX11800/ MAX11801 LOGIC) PUR, PUF, TDM YPANEL YMSW PUR, PUF, TDM MAX11800– MAX11803 Figure 6. Touch-Detection Circuitry ______________________________________________________________________________________ 21 Low-Power, Ultra-Small Resistive Touch-Screen Controllers with I2C/SPI Interface MAX11800–MAX11803 FAST PULLUP TOUCH DETECTION DIGITAL WAVEFORM DATA VALIDITY IS DETERMINED (DATA IS TAGGED) (NOTE: INCREASED CURRENT IN PUR MODE DURING TOUCH) SCAN MODE MEASUREMENT COMPLETE— DATA IS KNOWN PUR MODE (OPTIONAL) POWER ASSISTED PULLUP PERIOD (10Ω) PUF MODE PANEL IS ALLOWED TO RESETTLE BEFORE DETERMINING DATA VALIDITY TOUCH DETECT IS THERE A TOUCH? YES = LPM. NO = TDM. ANALOG WAVEFORM VDD TSC INPUT TOUCH NOT PRESENT: TSC INPUT REMAINS HIGH INITIAL INPUT VOLTAGE DETERMINED BY LAST SCAN ACTIVITY FORCED FAST PULLUP USING 10Ω SWITCH TOUCH PRESENT: TSC INPUT PULLED LOW TIME NORMAL TOUCH DETECTION DIGITAL WAVEFORM (NOTE: NO PUR PERIOD; ALLOW LONG PULLUP TIMES) DATA VALIDITY IS DETERMINED (DATA IS TAGGED) SCAN MODE MEASUREMENT COMPLETE— DATA IS KNOWN PUF MODE PANEL IS ALLOWED TO RESETTLE BEFORE DETERMINING DATA VALIDITY (THROUGH 50kΩ/100kΩ PULLUP) TOUCH DETECT IS THERE A TOUCH? YES = LPM. NO = TDM. ANALOG WAVEFORM VDD TSC INPUT TOUCH NOT PRESENT: TSC INPUT PULLED HIGH THROUGH 50kΩ/100kΩ PULLUP INITIAL INPUT VOLTAGE DETERMINED BY LAST SCAN ACTIVITY TOUCH PRESENT: TSC INPUT PULLED LOW BY PANEL TIME Figure 7. Touch-Detection Operations 22 ______________________________________________________________________________________ Low-Power, Ultra-Small Resistive Touch-Screen Controllers with I2C/SPI Interface Combined Commands Combined commands reduce AP interaction with the MAX11800–MAX11803 by allowing multiple measurements. For example, the MAX11800–MAX11803 can be instructed to provide X and Y data, or X and Y and Z1 data, or X and Y and Z1 and Z2 data using a single command. Data Tagging In direct conversion modes, all measurement data is contained in a 16-bit word. X, Y, Z1, and Z2 information is logged independently. Each word consists of 12 bits of measurement data plus a 2-bit measurement type (MTAG) and a 2-bit event tag (ETAG). The measurement tag identifies whether the data represents an X, Y, Z1, or Z2 result. The event tag indicates the point at which the data is sampled (initial, midpress, or release) during the touch event. When trying to read a result which is pending an update, the entire data stream is read back as FFFFh and the event tag as 11b, indicating that the corresponding measurement is in progress and that the data stream is to be ignored. For combined commands, all data locations requested by the command are marked FFFFh, pending the completion of the entire command and the proper tagging of the data. See Table 5. Direct conversion modes do not use the internal FIFO or support the aperture (see the Aperture Modes and Options section) function. Each measurement type is afforded a single location in the memory. The AP must retrieve the data from the last requested measurement before moving on to the next measurement of the type. Auxiliary measurement data is not tagged because it is not related to panel operation. Auxiliary measurement data is stored and read back identically to the other direct conversion data. The tag locations for auxiliary measurement data are always set to 0000b, unless the read occurs when an auxiliary measurement is in progress. In this situation, the tag locations read 1111b and the data stream reads back FFFFh. MAX11800–MAX11803 Low-Power Modes There are also two low-power modes, LPM and TDM. During LPM, all circuitry is off, including the on-chip touch-detect pullup resistors used in the touch-detect circuitry. In direct conversion modes, a user-request initiates the next operation and all circuitry is off until a user-command is received. Therefore, the current consumption is primarily due to junction leakage. In autonomous conversion mode, an on-chip oscillator and timer are constantly running. Therefore, the device current consumption is primarily determined by the oscillator and timer. During TDM, all circuitry is off except the on-chip pullup resistor. This is an untimed mode (oscillator and timer are off) for both ACM and DCM (no digital current). This mode only consumes current through the on-chip pullup resistor when a touch is present. Table 4. Median Averaging Operations AVERAGING MODE 1 2 3 NUMBER OF SAMPLES TAKEN 4 8 16 NUMBER OF HIGH SAMPLES REMOVED 1 2 4 NUMBER OF LOW SAMPLES REMOVED 1 2 4 NUMBER OF REMAINING SAMPLES AVERAGED 2 4 8 Table 5. Data Word Structure (All Direct Conversion Modes) INDEX Byte 12-Bit Content 8-Bit Content 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 Event Event 0 MSB Byte Position MSBs Position Data Position LSBs Trailing Zeros LSB Byte Measure Measure ______________________________________________________________________________________ 23 Low-Power, Ultra-Small Resistive Touch-Screen Controllers with I2C/SPI Interface MAX11800–MAX11803 Panel Setup, Measurement, and Scan Commands To simplify measurement procedures, the MAX11800– MAX11803 support three types of commands: panel setup commands (PSU), panel measurement commands (PMC), and combined measurement commands (CMC). In direct conversion mode, the MAX11800–MAX11803 can use all three types of commands. Using individual panel setup and measurement commands allow for a high degree of customization based on decisions made by the AP, while using combined commands significantly simplifies the complete measurement process and reduces communications between the AP and the MAX11800–MAX11803. In autonomous mode, the MAX11800–MAX11803 use combined commands to control and automate all aspects of panel setup, measurements, and timing. See the Operating Mode Configuration Register (0x0B) section for more details. combinations of measurements (X and Y, X and Y and Z1, or X and Y and Z1 and Z2 combined). Unlike autonomous conversion modes, the AP maintains control over the initiation of panel setup, measurements events, and the sampling frequency. Figure 8 shows the state machine transitions for direct conversion mode. Interrupt Modes The MAX11800–MAX11803 support two direct conversion interrupt modes. The two direct conversion modes are the continuous interrupt mode (CINT) and the edge interrupt mode (EINT). Continuous Interrupt Mode In continuous interrupt mode, the panel returns to TDM and idle. The current status of the panel is then sent through TIRQ. The continuous interrupt mode is the least efficient mode in current consumption for long duration of touches. The power consumption is approximated by PTOUCH = VDD2/RPU. The power consumption levels observed when the panel is not touched is limited by the junction leakage currents of the MAX11800–MAX11803. Direct Conversion Mode Operations In direct conversion mode, the AP requests individual panel setup and conversion operations or automated NO COMMAND SETUP X PANEL TOUCH DETECT TIME IS UP NO COMMAND SETUP Y PANEL SETUP Z PANEL NO COMMAND X DETECT DONE AND CONTINUOUS AUX ACQUIRE Y ACQUIRE Z1 ACQUIRE Z2 ACQUIRE DONE AND CONTINUOUS T NO ND T A OUS LAS TINU N CO T NO ND T A OUS LAS TINU N CO NO CO T LA NT ST INU OR OU S AVERAGE CONVERSION LAST CONVERSION AVERAGE CONVERSION NO CO T LA NT ST INU OR OU S LAST CONVERSION USER COMMAND INTERNAL TRANSITION TOUCHDETECT FINE PULLUP TIME IS UP TOUCHDETECT FINE PULLUP Figure 8. State Machine Transitions (Direct Conversion Mode) 24 ______________________________________________________________________________________ Low-Power, Ultra-Small Resistive Touch-Screen Controllers with I2C/SPI Interface The MAX11800–MAX11803 idle in TDM. The TIRQ output goes low when a touch is detected on the panel indicating to the AP that a touch is present and a measurement operation starts. The AP requests specific panel measurements through the serial interface. TIRQ stays low during panel setup and measurement operations. Once a measurement is complete (with CONT = 0), the MAX11800–MAX11803 check for the continued presence of a touch on the panel and tag the data accordingly (see Table 6). The duration of this operation is programmable, specified in the touch-detect pullup timing configuration register (0x07). After the data is tagged, the data is available for readback through the serial interface. The MAX11800–MAX11803 return to TDM and return control of TIRQ to the TDM circuitry. TIRQ stays low while a touch remains present, indicating further measurements are required, otherwise TIRQ goes high until a new touch is observed. Continuous interrupt mode (CINT) allows the complete control over the measurement operations and direct observation of the touch status of the panel. Figure 9 shows the polling of TIRQ when other functions share the TIRQ bus. In the illustration of Figure 9, no ‘10’ event tag is observed because the release occurs during a TDM period. Edge Interrupt Mode When a touch is present on the panel in edge interrupt mode, the MAX11800–MAX11803 return to an untimed high-impedance mode once data tagging operations are complete. In edge interrupt mode, the duration of a touch is determined by the tags applied to the measurement data. Data tagged as initial (00) or midpress (01) indicates the user needs to continue to scan the panel until a release is observed. In this state, there is no need to continue monitoring the touch status prior to the next requested measurement. If a panel touch is not present, data is tagged as release (10) and the MAX11800–MAX11803 idle in TDM continuously, issuing an interrupt only when the next panel touch is initiated. The operation described in the preceding paragraph makes the edge interrupt mode more efficient than the continuous interrupt mode. However, the edge interrupt mode requires continuous scanning of the panel until a release (10) event is observed. Otherwise, the MAX11800–MAX11803 do not idle in TDM and are not able to recognize a change in touch status. New touches are not recognized and new interrupts are not issued if a release event is not detected before stopping the conversion sequence. MAX11800–MAX11803 Table 6. Measurement and Event Tags (Continuous Interrupt Mode) MEASUREMENT X Y Z1 Z2 EVENT Touch (data valid) N/A (not used) No touch present (data invalid) Measurement in progress (data invalid) MTAG[3:2] 00 01 10 11 ETAG[1:0] 00 01 10 11 BEGINNING OF TOUCH EVENT PANEL END OF TOUCH EVENT TIRQ TDM DCM SCAN ETAG = 00 TDM DCM SCAN ETAG = 00 tAP tSD TDM DCM SCAN ETAG = 00 TDM READBACK OPERATIONS ARE NOT SHOWN, BUT ARE EXECUTED DURING TDM PERIODS. SCAN INTERVAL (tAP) IS CONTROLLED BY THE AP AND THE INITIATION OF DM SCAN EVENTS. SCAN DURATION (tSD) IS A FUNCTION OF THE SCAN TYPE AND CONFIGURATION SETTINGS. Figure 9. Continuous Interrupt Mode (Direct Conversion Mode) ______________________________________________________________________________________ 25 Low-Power, Ultra-Small Resistive Touch-Screen Controllers with I2C/SPI Interface The EINT mode reduces TIRQ activity. During EINT, the MAX11800–MAX11803 idle in a TDM. TIRQ goes low when a new touch is detected on the panel. TIRQ stays low for a fixed duration as specified in the configuration register 0x01, indicating to the AP that a touch is present and measurements are required. The AP requests specific panel setups and measurements through the serial interface using panel setup and conversion commands after TIRQ goes low. Once a measurement is complete (with CONT = 0), the MAX11800–MAX11803 check for the continued presence of a touch and tag the data accordingly. See Table 7. The duration of this operation is programmable, specified in the T ouch-Detect Pullup Timing Configuration Register (0x07) section. After the data is tagged, it is available for readback through the serial interface. The MAX11800–MAX11803 do not return to TDM when the panel touch is still present (ETAG = 00, 01), but remain in an LPM awaiting further measurement commands. The devices return to TDM when the panel touch is no longer present (ETAG = 10) and return control of the TIRQ interrupt to the TDM circuitry to await the next touch event. After a touch is indicated, the AP must continue to issue conversion commands until the touch is removed alerting the AP when the panel is released (by ETAG = 10). The MAX11800–MAX11803 return to TDM and observe the start of the next touch event. Panel commands MAX11800–MAX11803 Table 7. Measurement and Event Tags (Edge Interrupt Mode) MEASUREMENT X Y Z1 Z2 EVENT Initial touch (data valid) Midpress (data valid) Release/no touch present (data invalid) Measurement in progress (data invalid) MTAG[3:2] 00 01 10 11 ETAG[1:0] 00 01 10 11 issued with CONT = 1 are not capable of fulfilling this requirement. The EINT mode provides the least interrupt activity and the lowest power consumption. Use EINT mode for general touch-screen applications and applications requiring high resolution in space and time. When the TIRQ bus is shared with other functions, poll the general status register (0x00) to detect the presence of an interrupt. See Figure 10. BEGINNING OF TOUCH EVENT PANEL END OF TOUCH EVENT TIRQ tIRQ TDM DCM SCAN ETAG = 00 LPM DCM SCAN ETAG = 01 LPM DCM SCAN ETAG = 10 TDM tAP tSD READBACK OPERATIONS ARE NOT SHOWN, BUT ARE EXECUTED DURING TDM PERIODS. TIRQ DURATION (tIRQ) IS SPECIFIED BY THE GENERAL CONFIGURATION REGISTER (0x01). SCAN INTERVAL (tAP) IS CONTROLLED BY THE AP AND THE INITIATION OF DM SCAN EVENTS. SCAN DURATION (tSD) IS A FUNCTION OF THE SCAN TYPE AND CONFIGURATION SETTINGS. Figure 10. Edge Interrupt Mode (Direct Conversion Mode) 26 ______________________________________________________________________________________ Low-Power, Ultra-Small Resistive Touch-Screen Controllers with I2C/SPI Interface MAX11800–MAX11803 Table 8. Panel Setup Command Summary HEX 6xh 6xh 6xh 6xh R6 1 1 1 1 R5 1 1 1 1 R4 0 0 0 0 R3 1 1 1 1 R2 0 0 1 1 R1 0 1 0 1 R0 (1) (1) (1) (1) ACCESS Write Write Write Write PAIRABLE No No No No COMMAND LENGTH 8 8 8 8 OPERATION X = panel setup Y = panel setup Z1 = panel setup Z2 = panel setup Panel Setup Commands Panel setup commands configure the touch panel prior to a measurement. Panel setup commands allow the panel to fully settle before performing a measurement. The panel setup command summary is shown in Table 8. See the register map in the Status and Configuration Registers section for details on the panel setup timing options for X, Y, Z1, and Z2 measurements. The continuation bit (CONT) of the panel setup command programs the MAX11800–MAX11803 to maintain the present panel setting at the end of the command (CONT = 1). Panel setup commands assume a logical progression to an appropriate measurement. For example, when the MAX11800–MAX11803 are in the X panel setup mode, the devices can proceed to an X measurement mode only. The devices return to LPM when an incompatible command follows a panel setup command. See Figure 11. Panel Measurement Commands A measurement command selects one of the four physical setup options: X, Y, Z1, or Z2. The panel measurement command summary is shown in Table 8. All panel measurement commands include timed intervals to power up both the internal ADC and the panel with programmable durations. The delayed conversion time (tD_CV, delayed conversion configuration register (0x06)) governs the time that the panel and the ADC need to settle prior to the initiations of conversions. The minimum delayed conversion time is 10μs, which is the time the internal ADC needs to power up. If more settling time is required, increase the panel settling time by delaying the conversion time or by adding an additional panel setup time (tPSU) using the panel setup timing configuration register (0x05). The advantage of using a dedicated panel setup time is that the ADC does not consume power during this interval. The required panel setup time is a function of the panel end-to-end resistance, the capacitance of the panel, and any board-level components. LPM N X PSU CMD Y N X MEAS CMD Y N Y PSU CMD Y Y MEAS CMD Y N N Z1 PSU CMD Y Z1 MEAS CMD Y N N Z2 PSU CMD Y Z2 MEAS CMD Y N Figure 11. Command and Measurement Flow (DCM) ______________________________________________________________________________________ 27 Low-Power, Ultra-Small Resistive Touch-Screen Controllers with I2C/SPI Interface MAX11800–MAX11803 Table 9. Panel Measurement Command Summary HEX 7xh R7 0 R6 1 R5 1 R4 1 R3 0 R2 0 R1 0 R0 (CONT) (0) ACCESS Write PAIRABLE No COMMAND LENGTH 8 FUNCTION X, Y = combined command measurement X, Y, Z1 = combined command measurement X, Y, Z1, Z2 = combined command measurement AUX = conversion X = measurement Y = measurement Z1 = measurement Z2 = measurement 7xh 0 1 1 1 0 0 1 (0) Write No 8 7xh 7 xh 7xh 7xh 7xh 7xh 0 0 0 0 0 0 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 0 0 1 1 1 1 1 1 0 0 1 1 0 1 0 1 0 1 (0) (0) CONT CONT CONT CONT Write Write Write Write Write Write No No No No No No 8 8 8 8 8 8 When using a measurement command with CONT = 1 in a direct conversion mode, the MAX11800–MAX11803 perform a data tagging operation at the conclusion of the command. The devices remain in the requested setup mode in preparation for the succeeding measurement. The panel does not return to TDM/LPM and the interrupt status is not modified as a result of a measurement command with CONT = 1 issued. See Figure 12. Combined Commands In direct conversion modes, the panel returns to a TDM at the conclusion of a combined command and all data are tagged accordingly. The MAX11800– MAX11803 then idle in a low-power mode determined by the interrupt mode selected. See Figure 13. Auxiliary Measurement Command The MAX11800–MAX11803 support measurement of an auxiliary input using the internal ADC in direct conversion mode only. When programmed, the devices sam- ple and quantize the voltage at AUX using VDD as the ADC reference. The MAX11800–MAX11803 store the result in the same manner as X, Y, Z1, and Z2 measurements, but do not add data tagging. The devices also support averaging functions. Auxiliary measurements do not require any panel setup procedure. There is no combined command which includes an auxiliary measurement. Register 0x0A specifies the configuration for auxiliary measurements. In CINT, the MAX11800–MAX11803 continue to monitor for the touch status of the panel. The devices report any change in touch status in real time during an auxiliary measurement procedure. When performing auxiliary measurements in edge interrupt mode, the MAX11800–MAX11803 temporarily suspend the panel touch monitoring. The devices notify the AP after the completion of the auxiliary measurement when a new touch occurs during the auxiliary measurement. 28 ______________________________________________________________________________________ Low-Power, Ultra-Small Resistive Touch-Screen Controllers with I2C/SPI Interface MAX11800–MAX11803 PANEL SETUP COMMANDS (DIRECT CONVERSION ONLY) PANEL SETUP (PSU) FOR X, Y, OR Z DRIVE SETTING IS MAINTAINED UNTIL NEXT COMMAND (FORCE CONT = 1). MEASUREMENT COMMANDS (DIRECT CONVERSION ONLY) SINGLE CONVERSION WITH CONT = 1 SETUP (tPSU + tD_CV) ADC ACQUISITION ADC CONVERSION PSU DATA IS LOGGED. SETTING IS MAINTAINED UNTIL NEXT COMMAND (CONT = 1). AVERAGED CONVERSION WITH CONT = 1 SETUP (tPSU + tD_CV) ADC ACQUISITIONi ADC CONVERSIONi PSU AVERAGED DATA IS LOGGED. SETTING IS MAINTAINED UNTIL NEXT COMMAND (CONT = 1). NAVG SINGLE CONVERSION WITH CONT = 0 SETUP ADC ACQ ADC CONV PUR (OPT) PUF DATA IS TAGGED AND LOGGED. THE MAX11800–MAX11803 RETURN TO LPM OR TDM, ACCORDING TO IRQ MODE. AVERAGED CONVERSION WITH CONT = 0 SETUP ADC ACQi ADC CONVi NAVG PUR (OPT) PUF AVERAGED DATA IS TAGGED AND LOGGED. THE MAX11800–MAX11803 RETURN TO LPM OR TDM, ACCORDING TO IRQ MODE. Figure 12. Panel Setup and Measurement Commands ______________________________________________________________________________________ 29 Low-Power, Ultra-Small Resistive Touch-Screen Controllers with I2C/SPI Interface MAX11800–MAX11803 X AND Y COMMANDS SINGLE CONVERSIONS X PSU X ACQ X CONV Y PSU Y ACQ Y CONV DATA EVENT TAGGING PUR (OPT) PUF AVERAGED CONVERSIONS X PSU X ACQ NAVGX X CONV Y PSU Y ACQ NAVGY Y CONV PUR (OPT) PUF X, Y, AND Z1 COMMANDS SINGLE CONVERSIONS X PSU X ACQ X CONV Y PSU Y ACQ Y CONV Z1 PSU Z1 ACQ Z1 CONV PUR (OPT) PUF AVERAGED CONVERSIONS X PSU X ACQ NAVGX X CONV Y PSU Y ACQ NAVGY Y CONV Z1 PSU Z1 ACQ NAVGZ1 Z1 CONV PUR (OPT) PUF X, Y, Z1, AND Z2 COMMANDS SINGLE CONVERSIONS X PSU X ACQ X CONV Y PSU Y ACQ Y CONV Z1 PSU Z1 ACQ Z1 CONV Z2 ACQ Z2 CONV PUR (OPT) PUF AVERAGED CONVERSIONS X PSU X ACQ NAVGX X CONV Y PSU Y ACQ NAVGY Y CONV Z1 PSU Z1 ACQ NAVGZ1 Z1 CONV Z2 ACQ NAVGZ2 Z2 CONV PUR (OPT) PUF Figure 13. Combined Commands 30 ______________________________________________________________________________________ Low-Power, Ultra-Small Resistive Touch-Screen Controllers with I2C/SPI Interface Autonomous Conversion Mode The MAX11800/MAX11801 perform measurements automatically and inform the AP when they are complete in autonomous conversion mode, reducing data transfers on the serial bus as well as generating fewer interrupt requests. Figure 14 shows the state machine transitions for autonomous conversion mode. MAX11800–MAX11803 POWER DOWN TIME IS UP TOUCHDETECT ROUGH PULLUP TIME IS UP AVERAGE CONVERSION LAST CONVERSION XY MODE XY TOUCHDETECT ROUGH PULLUP TIME IS UP TOUCHDETECT FINE PULLUP TIME IS UP TOUCH DETECT Z1 Z2 LA ST MO NO TL AS T DE Y ACQUIRE SETUP Z PANEL TIME IS UP TIME IS UP NO TOUCH TOUCHDETECT FINE PULLUP TIME IS UP TOUCH DETECT AVERAGE CONVERSION SETUP Y PANEL Z1 ACQUIRE AVERAGE CONVERSION LAST CONVERSION AS TL NO LAST CONVERSION AVERAGE CONVERSION LAST CONVERSION Z2 ACQUIRE SETUP X PANEL TIME IS UP X ACQUIRE Figure 14. State Machine Transitions––Autonomous Conversion Mode ______________________________________________________________________________________ LA ST LA ST T NO TL T LA ST AS TOUCH IS PRESENT NO TL AS T 31 Low-Power, Ultra-Small Resistive Touch-Screen Controllers with I2C/SPI Interface MAX11800–MAX11803 Measurement Operations In autonomous conversion, the MAX11800/MAX11801 idle in TDM until a touch event occurs. The MAX11800/MAX11801 begin an automated sequence of measurements as defined by the configuration register 0x08h. The MAX11800/MAX11801 tag and log the data into the FIFO once a measurement is taken. If a touch is still present, the devices continue to idle in a LPM until the time, as set by the configuration settings, expires. If no touch is present at the expiration of the time set by the configuration settings, the MAX11800/MAX11801 return to TDM to await the next panel touch. All measurement operations occur without any intervention from the AP. The MAX11800/MAX11801 issue interrupts when new data is available in the internal FIFO. The device clears the interrupt when all data is read back. The AP controls the readback of measurement data as the data becomes available. Combined Commands I n autonomous conversion mode, the MAX11800/ MAX11801 automatically perform the combined command defined in the configuration register. The devices continuously scan for panel touch events. Between scans, the devices idle in a low-power mode according to the present touch status. Clear-on-Read Interrupt Mode T he MAX11800/MAX11801 control the progression through modes in clear-on-read mode. When the panel touch is present, the MAX11800/MAX11801 return to a timed high-impedance LPM to minimize current, after the data tagging operations are complete. The MAX11800/MAX11801 idle in LPM until it is time to perform the next required scan, determined by the configuration register settings. When a touch is not present at the end of a measurement, the device returns to idle in TDM. In TDM, the device waits until a touch is detected before initiating another set of autonomous measurements. The MAX11800/MAX11801 adopt a clear-on-interrupt protocol (CORINT) when in autonomous conversion mode. Between touch events, the devices idle in a lowpower TDM state. Upon detection of a touch, the devices begin a sequence of automated measurements. Each time a qualifying measurement is completed, the data for that measurement is written to the internal FIFO. Qualifying measurements are measurements that indicate the beginning and end of a touch event, which meet aperture requirements (see the Aperture Range Requirements section). TIRQ issues an interrupt once a qualifying measurement is completed and logged into the FIFO indicating that new data is available for the AP to read back. The MAX11800/MAX11801 continue to perform measurements as required by the configuration settings. Program the AP to service the interrupt immediately to avoid a FIFO overflow and loss of data. TIRQ remains asserted until all unread FIFO data has been read back to the AP. The AP confirms that readback is complete either by monitoring TIRQ or by monitoring the data event tags embedded in the data for end-of-FIFO. (ETAG = 11b). See Figure 15. END OF TOUCH EVENT BEGINNING OF TOUCH EVENT PANEL DATA WRITTEN TO FIFO, INTERRUPT ISSUED TIRQ AP READBACK, INTERRUPT CLEARED INTERRUPT IS HELD PENDING AP READBACK (FIFO STORES DATA) SCAN BLOCK TDM LPM ACM SCAN ETAG = 00 tSD tSP ACM SCAN ETAG = 01 LPM ACM SCAN ETAG = 10 TDM tINIT READBACK OPERATIONS ARE NOT SHOWN, INDICATED BY THE CLEARING OF THE AP-INITIATED INTERRUPT. WAIT TIME BETWEEN TOUCH DETECTION AND INITIAL SCAN (tINIT) IS SPECIFIED BY CONFIGURATION SETTINGS. SCAN DURATION (tSD) IS A FUNCTION OF THE SCAN TYPE AND CONFIGURATION SETTINGS. SCAN PERIOD (tSP) IS CONTROLLED BY CONFIGURATION SETTINGS. Figure 15. Clear-on-Read Interrupt Operation 32 ______________________________________________________________________________________ Low-Power, Ultra-Small Resistive Touch-Screen Controllers with I2C/SPI Interface Delayed Touch Detection During Mode Transitions The MAX11800/MAX11801 support a low-power powerdown mode suspending all touch-screen activity and the panel is not driven. In this mode, the MAX11800/MAX11801 is unable to detect a touch. When commanded to transition from PWRDN to any normal mode of operation, the MAX11800/MAX11801 go through a PUR/PUF sequence prior to observing the panel touch status, minimizing the occurrence of interrupts issued by false touches caused by the initial state of panel capacitances. In addition, when commanded to transition between normal operating modes, the MAX11800/MAX11801 clear any existing interrupts and go through the PUR/PUF sequence prior to observing the current panel touch status. FIFO Memory The MAX11800/MAX11801 include an internal FIFO to store scan block results for readback through the AP. Each scan block result contains complete data for all measurements requested by the scan type (X, Y; or X, Y, Z1; or X, Y, Z1, Z2). The depth of each scan data block ranges from 32 bits (X, Y mode) to 48 bits (X, Y, Z1 mode) or 64 bits (X, Y, Z1, and Z2 mode). The internal FIFO stores up to 16 complete scan blocks, a total of 1024 bits. Regularly service the FIFO to prevent overflow conditions. In the event of an overflow, the FIFO ceases to write new data until the old data is read or cleared. Avoid overflow to prevent data loss and unreliable behavior. Check the general status register (0x00) and the FIFO overflow bit to determine if the FIFO is in overflow. The FIFO overflow bit asserts when a data overflow occurs. See the Clearing FIFO section. Clearing FIFO Write to the operating mode configuration register (0x0B) to clear the FIFO. Modifying the contents of the register is not necessary as any write operation to this register location clears the FIFO and the interrupt TIRQ (if present). The FIFO completely clears when autonomous conversions halt and the MAX11800/MAX11801 transition to direct conversion mode. The FIFO also clears on transitions from direct conversion mode to autonomous mode. MAX11800–MAX11803 FIFO Data Block Readback Structure Table 10 illustrates the scan data block structure within the FIFO for each scan type. Block boundaries are indicated by bold lines. Numeric subscripts denote the sample order when the data was taken. Readback proceeds from top to bottom. FIFO blocks are written as a complete unit with an interrupt issued only after all required block measurements are complete and data is tagged. A FIFO data block consists of 2 to 4 FIFO data words. Table 10. FIFO Data Block Structure 2-WORD BLOCK (X, Y) X1 MSB X1 LSB Y1 MSB Y1 LSB X2 MSB X2 LSB Y2 MSB Y2 LSB X3 MSB X3 LSB Y3MSB Y3 LSB X4 MSB X4 LSB Y4 MSB Y4 LSB 3-WORD BLOCK (X, Y, Z1) X1 MSB X1 LSB Y1 MSB Y1 LSB Z11 MSB Z11 LSB X2 MSB X2 LSB Y2 MSB Y2 LSB Z22 MSB Z22 LSB . . . . 4-WORD BLOCK (X, Y, Z1, Z2) X1 MSB X1 LSB Y1 MSB Y1 LSB Z11 MSB Z11 LSB Z21 MSB Z21 LSB X2 MSB X2 LSB Y2 MSB Y2 LSB Z12 MSB Z12 LSB Z22 MSB Z22 LSB ______________________________________________________________________________________ 33 Low-Power, Ultra-Small Resistive Touch-Screen Controllers with I2C/SPI Interface FIFO Data Word Structure Table 11 shows a 16-bit data word (MSB byte + LSB byte). Each data word consists of 12 bits of position data, mapped to locations [15:4]. Eight-bit measurement data are left-adjusted and mapped to locations [15:8] and followed by four trailing zeros. Table 12 shows a 2-bit measurement tag indicating the measurement type (X, Y, Z1, or Z2), appended in locations [3:2]. Table 13 shows a 2-bit event tag indicating where the sample occurs within a touch event (initial, midpress, or release) in locations [1:0]. All data for a given scan operation is tagged according to the touch status observed at the end of the scan block measurement operations. For example, if a requested X, Y, Z1, Z2 scan block contains a release event, all the data words are tagged 10 before being written to the FIFO. An event tag of 11 indicates that the data readback operation reaches the end of the current FIFO data log (end of file marker) and there is no unread data in the FIFO. Terminate the readback operation to await the next interrupt. Ignore all data with the 11 event tag. Block Readback Operations The MAX11800/MAX11801 do not support partial block readback operations. Each readback operation loads an entire scan block result (32, 48, or 64 bits) into a temporary location for serial readback. A scan block is marked as read in the FIFO once a scan block result is loaded, freeing the memory space for the subsequent measurements. Once initiated, the AP must complete the full readback cycle for the block requested or the unread portions of the block data is lost. MAX11800–MAX11803 Clearing Interrupt The FIFO is only used in the autonomous mode with the clear-on-read interrupt. The interrupt is cleared only when the newest data block currently available in the FIFO is loaded for readback. The interrupt does not clear if there is any unread data block remaining in the FIFO once a scan block result is loaded. The FIFO does not check for partial block readbacks. Once the last available FIFO data block is loaded for readback, the interrupt clears regardless of whether the readback operation for that block is complete. Aperture Modes* and Options The aperture modes available with the MAX11800/ MAX11801 implement spatial filtering. The MAX11800/ MAX11801 contain the required logic to examine panel measurement data and determine if the data meets the aperture requirements to be written to the FIFO. Aperture testing decreases the number of entries in the FIFO to the minimum required to implement the intended application. The elimination of extraneous FIFO data events reduces activity on the TIRQ line, serial bus, and minimizes AP overhead. The contents in the FIFO are not necessarily linearly sampled in time when the device is in aperture mode. Aperture Range Requirements Program the aperture range requirements for both X and Y through register 0x0B. Range requirements are expressed as distance, in position LSBs. The blanking aperture extends from the initial touch position, both ±ΔX and ±ΔY with 12-bit resolution (1 LSB = 1/4096 of the corresponding screen dimension). An aperture setting of 0x00 effectively disables aperture checking with all measurement data logged to the FIFO. Apertures are specified in a power-of-two format: ΔX = 2APRX[3:0]-1 and ΔY = 2APRY[3:0]-1. 8 7 6 5 4 3 2 1 Event Event 0 Table 11. FIFO Data Word Structure INDEX Byte 12-Bit Content 8-Bit Content 15 14 13 12 11 10 9 MSB Byte Position MSBs Position Data Position LSBs Trailing Zeros LSB Byte Measure Measure Table 12. FIFO Data Measurement Tags MEASUREMENT X Y Z1 Z2 TAG[3:2] 00 01 10 11 Table 13. FIFO Event Tags EVENT Initial touch Midpress Release (data invalid) End of file indicator (FIFO data invalid) TAG[1:0] 00 01 10 11 *Patented feature. 34 ______________________________________________________________________________________ Low-Power, Ultra-Small Resistive Touch-Screen Controllers with I2C/SPI Interface For example: 0000 = 2-1 LSB = aperture checking disabled 0001 = 2(1-1) LSB = ±1 LSB 0010 = 2(2-1) LSB = ±2 LSB 0011 = 2(3-1) LSB = ±4 LSB … 1001 = 2(9-1) LSB = ±256 LSB (1/16 of the screen in each direction) 1010 = 2(10-1) LSB = ±512 LSB (1/8 of the screen in each direction) 1011 = 2(11-1) LSB = ±1024 LSB (1/4 of the screen in each direction) 1100 = 2(12-1) LSB = ±2048 LSB (1/2 of the screen in each direction) 1101 to 1111 = aperture checking disabled Applications Information Using Aperture Mode The MAX11800/MAX11801 accommodate touch-panel applications where limited resolution in both time and space can be traded off for reduced microprocessor activity. A simulated keypad is an example of an application where autonomous conversions with aperture checking yield an efficient solution. The AP determines the durations of touch-screen presses. An issuance of TIRQ interrupts accompanies all FIFO events. The interrupts clear when all existing data is read back by the AP, allowing the AP to correctly interpret held panel data. The FIFO updates immediately when a new touch event is detected. The system assumes that the panel touch is continuous after the AP receives the interrupt. The MAX11800/MAX11801 continue to scan the panel at the user-programmed sample rate. The FIFO updates when the measurement data shows that the panel touch location moves (i.e., a measurement exceeds either of the selected aperture ranges). The FIFO also updates upon detection of a panel release. The AP determines the duration of the press by observing the time between the leading edge of the touch (tag 00) and the release edge of the touch (tag 10). All midpress data (tag 01) are interpreted as part of a dragged touch event. All valid touch events log two data points into the FIFO: an initial data point at the beginning of the touch (tag 00) and a release data point at the termination of the touch (tag 10). Discard release edge position data as invalid as the MAX11800/MAX11801 cannot determine at which point in the ADC conversion cycle the panel is released during the measurement operation. If the release occurs while the ADC is actively sampling the panel, the results are invalid. Only initial and midpress position data are reliable. Any touch event too short in duration to log both initial and release data points is recorded in the FIFO as a release (tag 10) and discarded as a glitch event. Measuring durations of panel touches becomes impractical when the AP services the MAX11800/ MAX11801 at lower than the operating speed of the devices and the panel combined. The AP cannot time the duration between panel touches when both the initial and release data points can be logged before the initial interrupt is serviced. Do not allow the FIFO to overflow as touch information can be lost and the FIFO content becomes invalid. MAX11800–MAX11803 FIFO Aperture Criteria In autonomous mode with aperture engaged, new data is written to the FIFO, and an interrupt is issued when the following conditions occur (aperture mode is not available in direct conversion mode). New Panel Touch Initiated The FIFO updates and issues an interrupt when a new touch is observed on the panel (data tag = 00). This event occurs regardless of the current aperture setting and the previous touch location so that multiple presses in the same location can be observed and registered. Continuous Panel Touch Terminated The FIFO updates and issues an interrupt when a continuous panel touch is terminated (data tag = 10). This event occurs regardless of the current aperture setting and the previous continuous touch location(s) so that multiple presses in the same location can be observed and registered. Continuous Panel Touch Measurement Meets Aperture Criteria The MAX11800/MAX11801 log the measurement data to the FIFO and issue an interrupt when a measurement during a continuous panel touch (event tag = 01) meets the aperture criteria (i.e., lies on or outside the aperture boundary). This event occurs when the point of contact is dragged across the touch screen. Only the ΔX or ΔY aperture criteria need to be met and a greater than or equal to qualification criterion is applied. If the change in X position or change in Y position exceeds the aperture criteria, then an interrupt is generated. ______________________________________________________________________________________ 35 Low-Power, Ultra-Small Resistive Touch-Screen Controllers with I2C/SPI Interface MAX11800–MAX11803 When the MAX11800/MAX11801 operate in autonomous conversion mode with low or no aperture ranges, the FIFO and interrupt activity occur frequently with the AP servicing the devices frequently to avoid loss of data due to limited FIFO depth. For this reason, do not perform autonomous conversion for applications where a high resolution in either space or time is required. Use direct conversion mode when requiring a high resolution in either space or time. that meet aperture requirements are enumerated and are shown with the corresponding aperture ranges. Positions 6 and 7 show a subsequent momentary press event. Figure 16 shows the anticipated interrupt waveforms in several operating modes. The first waveform shows interrupt operation assuming that aperture mode is enabled (with ΔX = ΔY = 4 LSBs), assuming that the AP service interrupts at a frequency faster than the selected TSC sample rate. Each qualifying sample induces a FIFO event and an interrupt pulse as shown. Timing between FIFO events can be timed by the AP to determine duration information. Table 14 shows the readback data assuming that the FIFO does not fill up. Examples of Using Aperture Mode Figure 16 shows an example of a touch sequence. A dragged touch sequence is initiated at position 1 and continues through to position 5. While multiple samples are taken during this sequence, only those samples PANEL TOUCH SPATIAL WAVEFORM 16 APER1 APER2 INITIAL TOUCH 1 DRAG ONE DRAG EVENT (1:5) AND ONE PRESS EVENT (6:7) SECOND RELEASE DRAG 7 6 SECOND TOUCH APER6 12 2 8 4 DRAG 3 4 DRAG APER4 APER3 0 4 8 12 16 20 24 5 INITIAL RELEASE INTERRUPT TIMING WAVEFORM 1 (ASSUMING FREQUENT SERVICING EVENTS WITH APERTURE MODE ENABLED) 1 2 3 4 5 6 7 INTERRUPT TIMING WAVEFORM 2 (ASSUMING FREQUENT SERVICING EVENTS WITH APERTURE MODE DISABLED) 1 2 3 4 5 6 7 INTERRUPT TIMING WAVEFORM 3 (ASSUMING INFREQUENT SERVICING EVENTS) (1) IRQ ISSUED (SERVICED) IRQ RELEASED NOTE: POSITION 5 IS LOGGED EVEN THOUGH POSITION 5 APPEARS IN APER4 BECAUSE POSITION 5 IS A RELEASE DATA POINT. IT IS THE SAME FOR POSITION 7. IF THE POSITION 6 TOUCH EVENT INITIATES WITHIN THE FINAL APERTURE FROM THE PREVIOUS EVENT (APER4), POSITION 6 IS LOGGED AS AN INITIAL TOUCH EVENT. Figure 16. Aperture Usage Example Waveforms 36 ______________________________________________________________________________________ Low-Power, Ultra-Small Resistive Touch-Screen Controllers with I2C/SPI Interface The second waveform shows an interrupt operation assuming that aperture mode is disabled (or that ΔX = ΔY = 0 LSB), assuming that the AP service interrupts at a frequency faster than the selected TSC sample rate. Every sample induces a FIFO event and an interrupt pulse as shown. The interrupt waveform is significantly busier than that shown in the first waveform. Duration information can now be directly determined from the FIFO samples since each sample is logged and occurs at the programmed sample rate. Table 15 lists the readback data assuming the FIFO does not fill up. The third waveform in Figure 16 shows an interrupt operation assuming that the MAX11800/MAX11801 are infrequently serviced. Ensure that the FIFO does not overflow. No duration information is available at resolutions below the servicing rate. Either the set of data shown in Table 14 or the set shown in Table 15 appears in the FIFO when read, depending on the aperture setting. MAX11800–MAX11803 Table 14. Readback and FIFO Contents with Aperture Mode Enabled SAMPLE 1 2 3 4 5 6 7 X 7 11 13 17 19 22 23 Y 11 9 5 7 6 14 15 TAG 00 01 01 01 10 00 10 Midpress event Midpress event Midpress event (last valid position data) Release event (end of first touch, ignore position data) Initial event (beginning of second touch) Release event (end of second touch, ignore position data) COMMENT Initial event (beginning of first touch) Table 15. Readback and FIFO Contents with Aperture Mode Disabled SAMPLE 1 1a 2 2a 2b 2c 3 3a 4 5 6 7 X 7 9 11 12 13 13 13 15 17 19 22 23 Y 11 10 9 8 7 6 5 6 7 6 14 15 TAG 00 01 01 01 01 01 01 01 01 10 00 10 Midpress event Midpress event Midpress event Midpress event Midpress event Midpress event Midpress event Midpress event (last valid position data) Release event (end of first touch, ignore position data) Initial event (beginning of second touch) Release event (end of second touch, ignore position data) COMMENT Initial event (beginning of first touch) ______________________________________________________________________________________ 37 Low-Power, Ultra-Small Resistive Touch-Screen Controllers with I2C/SPI Interface MAX11800–MAX11803 SPI Communication Sequence (MAX11800/MAX11802) The SPI interface consists of three inputs, DIN, DCLK, CS, and one output, DOUT. A logic-high on CS disables the MAX11800/MAX11802 digital interface and places DOUT in a high-impedance state. Pulling CS low enables the MAX11800/MAX11802 digital interface. The MAX11800/MAX11802 provide two possible implementations of SPI instructions. In rising-edge-driven operations, the devices are able to run at maximum clock speeds. Carefully consider the hold time requirements of the MAX11800/MAX11802 and minimize board skew contributions when running the MAX11800/MAX11802 at maximum clock speed. In falling-edge-driven operations, the device is less sensitive to board skew contributions, but slower clock speeds are required to meet the MAX11800/MAX11802 setup time requirements. For the MAX11800/MAX11802, read patterns output data is either latched on the rising edge running at maximum clock rates or on the falling edges running at reduced clock rates. SPI Configuration Register Write (MAX11800/MAX11802) Figure 17 shows the supported write operation sequence for the MAX11800/MAX11802. A single configuration register can be written in a 2-byte operation, composed of a target register address (A[6:0], plus a write mode indicator bit) followed by data to be written to the target register (D[7:0]). During write sequences, the DOUT line is not accessed by the SPI. DOUT remains high impedance throughout the command. Using the optional bus holder, the DOUT line retains the previous value unless altered by a device sharing the bus. The MAX11800/MAX11802 SPI interface supports multiple register write operations within a single sequence as shown in Figure 18. By repeating the address plus data byte pairs (in write mode), an unlimited number of registers can be written in a single transfer. Do not permit to combine write and read operations within the same SPI sequence. CS 1 SCLK 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 DIN A6 A5 A4 A3 A2 A1 A0 Wb D7 D6 D5 D4 D3 D2 D1 D0 Figure 17. SPI Single Configuration Register Write Sequence CS 1 SCLK 7 9 17 23 25 32 DIN An [6:0] Dn [7:0] Am [6:0] Dm [7:0] Figure 18. SPI Multiple Configuration Register Write Sequence 38 ______________________________________________________________________________________ Low-Power, Ultra-Small Resistive Touch-Screen Controllers with I2C/SPI Interface SPI Configuration or Result Register Read (MAX11800/MAX11802) Figure 19 shows the read operation sequence for the MAX11800/MAX11802. A single configuration register can be read back in a 2-byte operation, composed of a requested register address (A[6:0], plus a read mode indicator bit) followed by the data contents from that register (D[7:0]). During read operations, the SPI takes control of the DOUT line following the eight SCLK rising edge. The SPI retains control of the DOUT line until CS rises, terminating the operation. To support multiple register readback operations, data continues to be ported following the 16th rising clock edge. For single-byte transfers, this sub-bit information can be ignored, shown as S, in Figure 19. The DOUT output on the MAX11800/MAX11802 includes an optional bus holder to prevent the DOUT line from maintaining an indeterminate state when vacated by the device in the absence of an external bus pullup or bus sharing devices. The bus holder is designed not to interfere with other drivers sharing the DOUT line and holds the last valid state of the line, regardless of source. Disable the bus holder when not needed. The MAX11800/MAX11802 support the combination of the DIN and DOUT lines. To avoid data contention and possible high current states, the master device must relinquish control of the combined line at the 8th clock rising edge, allowing the MAX11800/MAX11802 to access the line through the end of the sequence. This is terminated on the rising edge of C S . See the S PI Timing Characteristics for relevant details. The MAX11800/MAX11802 also support multiple register readback operations using a single command. The protocol requires the user to supply an initial starting register location, followed by an unlimited number of clock pulses for data readback. The first data read back is from the start register. The MAX11800/MAX11802 internal autoincrement counter manages the data readback in later cycles. If autoinCS 1 SCLK DIN A6 A5 A4 A3 A2 A1 A0 R 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 crement is supported, the next register location is read back. If not, the last valid register location is read back (see the Command and Register Map section for the autoincrement attributes of each register). The following example shows a valid sequence for the readback of three register locations (Di through Di+2). The autoincrement reads only the X, Y, Z1, Z2, and AUX result registers preventing inadvertent readback of unrelated or reserved data locations. For example, if beginning at the XMSB register, a user can cycle through the XLSB register to the YMSB register and so forth up to the AUXLSB register. The MAX11800/MAX11802 do not autoincrement beyond the AUXLSB register. If clock cycles continue to be given, the AUXLSB register readback is repeated. The FIFO register does not autoincrement, which allows multiple readbacks of the same location. This allows the access of multiple FIFO memory blocks with a single read operation. When reading back FIFO registers, data management is handled in blocks not bytes. As a result, when an SPI read operation supplies at least one cycle of readback of the first byte of a FIFO block, the entire block is marked as read, regardless of whether the block or even byte readback is run to completion. To illustrate, assume the MAX11800 is in autonomous mode performing XY conversions and a FIFO readback is requested starting at register 0x50. Clock cycles 9 to 40 are required to complete the readback of the first available FIFO blocki = {XMSBi, XLSBi, YMSBi, YLSBi} with the device updating in response to the 8th to 39th clock rising edges. The host processor can complete the readback data latching of YLSBi[0] either on the 39th falling edge or the 40th rising edge. To support a continued readback of further FIFO blocks, the device updates the DOUT line to XMSBi+1[7] in response to the 40th clock rising edge (though blocki+1 is not marked as read). If the AP supplies a 42nd clock rising edge, the FIFO blocki+1, if present, is marked as read, regardless of whether any further clock cycles are provided. MAX11800–MAX11803 DOUT D7 D6 D5 D4 D3 D2 D1 D0 S Figure 19. SPI Single-Byte Register Read Sequence ______________________________________________________________________________________ 39 Low-Power, Ultra-Small Resistive Touch-Screen Controllers with I2C/SPI Interface MAX11800–MAX11803 SPI Conversion Command (MAX11800/MAX11802) The sequence below shows the required command format for issuing conversion requests. A conversion request cannot be paired with multiple commands or instructions. Any conversion command issued while previous commands are being executed is ignored. ically a microcontroller) initiates data transfer on the bus and generates SCL. The I2C device address is 10010xx; the last 2 bits of the I2C address are userconfigurable through the address inputs A[1:0]. I2C-Supported Sequence (MAX11801/MAX11803) The MAX11801/MAX11803 feature an I2C-compatible, 2-wire serial interface consisting of a bidirectional serial data line (SDA) and a serial clock line (SCL). SDA and SCL facilitate bidirectional communication between the MAX11801/MAX11803 and the master. The master (typCS 1 SCLK DIN DOUT Ai[6:0] Di[7:0] 7 8 9 16 I2C Configuration Register Write (MAX11801/MAX11803) Repeat the register address plus data pairs (byte 2 and byte 3 in Figures 21, 22, and 23) to perform multiple register writes. There is no limit to the number of registers written with a single command. For example, the I2C master can perform multiple register writes to set up all required conversion options, and then issue a separate I2C command to start a conversion process. 17 24 25 32 Di+1[7:0] Di+2[7:0] S Figure 20. SPI Multiple-Byte Register Read Sequence CS 1 SCLK 2 3 4 5 6 7 8 DIN A6 A5 A4 A3 A2 A1 A0 Wb Figure 21. SPI Conversion Command WRITE ADDRESS BYTE 1: DEVICE ADDRESS 1 0 0 1 0 A1 A0 W A N WRITE REGISTER NUMBER BYTE 2: FIRST REG NUMBER = N N N N N N N N A D WRITE DATA BYTE 3: REG(N)[7:0] DATA D D D D D D D A START SDA SCL STOP Figure 22. I2C Single Register Write Sequence START SDA SCL 1 WRITE ADDRESS BYTE 1: DEVICE ADDRESS 0 0 1 0 A1 A0 W A N WRITE REGISTER NUMBER BYTE 2: REG NUMBER = N N N N N N N N A D WRITE DATA BYTE 3: REG(N)[7:0] DATA D D D D D D D A Z WRITE REGISTER NUMBER BYTE 4: REG NUMBER = Z Z Z Z Z Z Z Z A D WRITE DATA BYTE 5: REG(Z)[7:0] DATA D D D D D D D A STOP Figure 23. I2C Multiple Register Write Sequence 40 ______________________________________________________________________________________ Low-Power, Ultra-Small Resistive Touch-Screen Controllers with I2C/SPI Interface I2C Configuration or Result Register Read (MAX11801/MAX11803) The read sequence does not limit the number of bytes to be read. The internal register counter keeps incrementing as additional bytes are requested. The first byte out is Reg(N) as shown in Figure 24. The next byte out is Reg(N+1). The next byte out is Reg(N+2), and so on. The programmer needs to keep track of the incremented register address. Acknowledge pulses from the master are not required to autoincrement the internal register location. The internal register location updates on each byte. See the Command and Register Map section for details governing the incrementing of register addresses. The autoincrement reads only the X, Y, Z1, Z2, and AUX result registers preventing inadvertent readback of unrelated or reserved data locations. For example, if beginning at the XMSB register, a user can cycle through the XLSB register to the YMSB register and so forth up to the AUXLSB register. The MAX11801/ MAX11803 do not autoincrement beyond the AUXLSB register. If clock cycles continue to be given, the AUXLSB register readback is repeated. The FIFO (MAX11801) register does not autoincrement, which allows multiple readbacks of the same location. This allows the access to multiple FIFO memory blocks with a single read operation. When reading back FIFO registers, data management is handled in blocks not bytes. As a result, when an I2C read operation supplies at least one cycle for readback of the first byte of a FIFO block, the entire block is marked as read. This is regardless of whether the block or even byte readback is run to completion. • Streamlined I 2C Read Operations (MAX11801/ MAX11803) The MAX11801/MAX11803 support several streamlined readback behavior to significantly improve data transfer efficiency. Using the streamlined readback sequence shown in Figure 25, data readback can commence following an assumed progression. Disable the streamlined readback feature to allow full readback sequence. • Resumed Read Operations (MAX11801/ MAX11803) When readback operations are suspended and later resume from the current (incremented) register location, it is not necessary to supply the initial device address and register start sequence. Begin the readback portion of the command following the streamlined sequence shown in Figure 25 to allow more efficient data transfer. For example, if the user accesses the FIFO register (MAX11801), which does not autoincrement, and reads several observations and then stops and resumes the readback operation at a later time, the user only needs to issue the streamlined readback sequence to continue to gather observations from the FIFO. Once the device is placed in autonomous mode, the user only needs to issue the full readback sequence once for the initial FIFO access. Then streamlined read access to the device resumes at the FIFO location, unless an intervening command is issued as shown in Figure 25. Similarly, when reading back result registers, begin with XMSB and autoincrement to XLSB, then stop. When readback resumes by the issuance of the streamlined readback sequence, data readback commences from the YMSB location. MAX11800–MAX11803 START SDA SCL 1 WRITE ADDRESS BYTE 1: DEVICE ADDRESS 0 0 1 0 A1 A0 W A WRITE REGISTER START NUMBER BYTE 2: FIRST REG NUMBER = N N N N N N N N N A REPEATED START 1 WRITE ADDRESS BYTE 3: DEVICE ADDRESS 0 0 1 0 A1 A0 R A D READ DATA BYTE 4: REG(N)[7:0] DATA D D D D D D D A READ DATA READ DATA (LAST BYTE) ADDITONAL SEQUENTIAL READ DATA BYTES D D D D D D D D ~A STOP ACKNOWLEDGE GENERATED BY MAX11801/MAX11803 ACKNOWLEDGE GENERATED BY I2C MASTER Figure 24. I2C Multiple Register Read Sequence START SDA 1 SCL WRITE ADDRESS BYTE 3: DEVICE ADDRESS 0 0 1 0 A1 A0 R A D READ DATA BYTE 4: REG(N)[7:0] DATA D D D D D D D A READ DATA READ DATA (LAST BYTE) ADDITONAL SEQUENTIAL READ DATA BYTES D D D D D D D D ~A STOP ACKNOWLEDGE GENERATED BY MAX11801/MAX11803 ACKNOWLEDGE GENERATED BY I2C MASTER Figure 25. I2C Streamlined Register Read Sequence ______________________________________________________________________________________ 41 Low-Power, Ultra-Small Resistive Touch-Screen Controllers with I2C/SPI Interface MAX11800–MAX11803 • Direct Conversion Read Operations (MAX11801/ MAX11803) In direct conversion mode, commands automatically set the readback target register and streamline data gathering. See the Command and Register Maps section for specific details for all such commands. The MAX11801/MAX11803 automatically set the default readback register to the XMSB location when a command requesting is received and a XY combined measurement is received. If the XY command is issued and allowed to complete, the device can then be followed directly by a streamlined read sequence and data readback commences from the XMSB register. Accepted direct conversion commands always modify the current internal register location and effectively override the resumed readback behaviors and any register settings made in response to previously completed direct conversion commands. • Read Operations Following Write Operations (MAX11801/MAX11803) Data readback commences from the last written register location when the streamlined readback sequence is issued following a configuration write operation. When modifying the contents of the operating mode configuration register (0x0B) using a write sequence, then issuing a streamlined readback sequence, the contents of register 0x0B are provided. Register write operations always modify the current internal register location and effectively override the resumed readback behaviors. are being executed is ignored and the readback target register is not modified. Command and Register Map The command map consists of the user-configuration registers (read/write), TSC data readback commands (read only), and TSC panel setup and conversion commands (write only). User-Accessible Registers There are six blocks of user-accessible registers and commands that control all operations of the MAX11800–MAX11803. The register blocks and commands consist of the following: 1) Status and Configuration Registers: 00h to 0Bh • Sets modes of operation––ACM or DCM • Settings to accommodate various panel sizes (panel time constant) • Averaging and noise settings • Measurement resolution • Auxiliary settings • General part status reporting 2) FIFO Data Readback Command: 50h • Autonomous conversion mode only (MAX11800/ MAX11801) • Allows reading FIFO contents when operating in ACM 3) Data Readback Commands: 52h to 5Bh • Direct conversion mode only (MAX11800/ MAX11802) • Allows reading measurement results when in DCM I2C Conversion Command (MAX11801/MAX11803) Figure 26 shows the required command format for issuing conversion requests. A conversion request cannot be paired with multiple commands or instructions. Any conversion command issued while previous commands START WRITE ADDRESS BYTE 1: DEVICE ADDRESS CONVERSION COMMAND STOP SDA SCL 1 0 0 1 0 A1 A0 W A N N N N N N N N A Figure 26. I2C Conversion Command 42 ______________________________________________________________________________________ Low-Power, Ultra-Small Resistive Touch-Screen Controllers with I2C/SPI Interface 4) I2C Readback Registers: 52h to 58h • Direct conversion mode only (MAX11801/ MAX11803) • Allows reading measurement results when in DCM 5) Panel Setup Commands: 6Ah to 6Fh • Sets up panel prior to making X, Y, Z1, or Z2 measurements 6) Measurement Commands: 70h to 7Fh • Performs specified measurement (X, Y, Z1, and/or Z2) The commands to read or write the user-accessible registers are always the same. However, the data format varies based on whether using an SPI or I2C interface. Tables 16 and 17 show the differences between SPI and I2C protocols. For SPI, the R/W bit is embedded in the 8-bit byte and always occupies the LSB position. For I2C, the protocol is always 8-bit byte followed by an acknowledge bit, for a total of 9 bits. The MSB in I2C format is always 0. In write mode, for I2C, the MSB is ignored internal to the MAX11800– MAX11803, so setting it to 0 or 1 has no effect. MAX11800–MAX11803 Status and Configuration Registers The status and configuration registers are located in block 0x00 to 0x0B. See Table 18. All user-configuration register write mode operations are pairable within the SPI/I2C interface. Multiple locations can be written under a single instruction with a register byte followed by a data. All user-configuration read-mode operations support autoincrement. For example, if location 0x00 is read back and more clock pulses are issued, readback will proceed through location 0x01 and so forth. The user should set all configuration registers to the desired values before issuing direct conversion operations or placing MAX11800/MAX11801 in autonomous mode. Table 16. SPI Command and Data Format: 8 Bits BYTE BIT 7 R6 BIT 6 R5 BIT 5 R4 BIT 4 R3 Command or Data BIT 3 R2 BIT 2 R1 BIT 1 R0 (CONT) BIT 0 R/W 1/0 Table 17. I2C Command and Data Format: 8 Bits Plus ACK BYTE BIT 7 0 BIT 6 R6 BIT 5 R5 BIT 4 R4 BIT 3 R3 BIT 2 R2 BIT 1 R1 BIT 0 R0 (CONT) ACK BIT 1/0 1/0 Command or Data ______________________________________________________________________________________ 43 Low-Power, Ultra-Small Resistive Touch-Screen Controllers with I2C/SPI Interface MAX11800–MAX11803 Table 18. Status and Configuration Registers HEX 00h 01h 02h 03h 04h 05h 06h 07h R6 R5 R4 R3 R2 R1 R0 ACCESS 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 1 1 1 0 0 1 1 0 0 1 1 0 1 0 1 0 1 0 1 R R/W R/W R/W R/W R/W R/W R/W PAIRABLE No Yes Yes Yes Yes Yes Yes Yes AUTOINCREMENT Yes Yes Yes Yes Yes Yes Yes Yes DATA LENGTH 8 8 8 8 8 8 8 8 FUNCTION General status General configuration Measurement resolution configuration Measurement averaging configuration ADC sample time configuration Panel setup times configuration ADC delay initial conversion configuration Touch-detect pullup times configuration Autonomous mode timing configuration (MAX11800/ MAX11801) Aperture settings (auto) configuration (MAX11800/ MAX11801) Auxiliary measurement configuration Operating mode configuration 08h 0 0 0 1 0 0 0 R/W Yes Yes 8 09h 0 0 0 1 0 0 1 R/W Yes Yes 8 0Ah 0Bh 0 0 0 0 0 0 1 1 0 0 1 1 0 1 R/W R/W Yes Yes Yes Yes 8 8 Data Readback Commands Autonomous Conversion Mode Use the readback command 0x50 to read back available FIFO data in autonomous conversion modes (AUTO = 1) (MAX11800/MAX11801). The oldest available data is read out first. Data blocks vary from 32 to 64 bits in length, depending on the scan mode selected. Reading back longer than one block results in reading back the next available block. The end-of-file indicator is read back when no unread data is available in the FIFO. This command does not autoincrement and the register address does not advance beyond 0x50. See the FIFO Data Block Readback Structure section for more details. Direct Conversion Mode Use the readback commands 0x52 to 0x5B to read back available measurement data gathered in direct 44 conversion mode (AUTO = 0). Random data access is supported within this register space and the commands autoincrement up to register 0x5B. The register address does not advance beyond register 0x5B. Attempting to read back a pending conversion results in data being tagged invalid. See the Direct Conversion Mode Operations section for more details. The panel setup and conversion commands are not pairable in write mode as each command modifies the panel setting both during and after the command, based on conversion executions and CONT bit settings. All direct conversion commands modify the expected I2C read register location to support the data streamlining protocol. Table 21 shows the resulting read register settings by command type applicable to I2C variants. ______________________________________________________________________________________ Low-Power, Ultra-Small Resistive Touch-Screen Controllers with I2C/SPI Interface MAX11800–MAX11803 Table 19. FIFO Data Readback Command (Autonomous Mode Only––MAX11800/MAX11801) HEX 50h R6 1 R5 0 R4 1 R3 0 R2 0 R1 0 R0 X ACCESS AUTOINCREMENT Read No DATA LENGTH INF OPERATION Read next available FIFO data block Table 20. Data Readback Commands (Direct Mode Only) HEX 52h 53h 54h 55h 56h 57h 58h 59h 5Ah 5Bh R6 1 1 1 1 1 1 1 1 1 1 R5 0 0 0 0 0 0 0 0 0 0 R4 1 1 1 1 1 1 1 1 1 1 R3 0 0 0 0 0 0 1 1 1 1 R2 0 0 1 1 1 1 0 0 0 0 R1 1 1 0 0 1 1 0 0 1 1 R0 ACCESS 0 1 0 1 0 1 0 1 0 1 Read Read Read Read Read Read Read Read Read Read AUTOINCREMENT Yes Yes Yes Yes Yes Yes Yes Yes Yes No DATA LENGTH 8 8 8 8 8 8 8 8 8 8 OPERATION X = MSB (direct conversion result) X = LSB (direct conversion result) Y = MSB (direct conversion result) Y = LSB (direct conversion result) Z1 = MSB (direct conversion result) Z1 = LSB (direct conversion result) Z2 = MSB (direct conversion result) Z2 = LSB (direct conversion result) AUX MSB (direct conversion result) AUX LSB (direct conversion result) Table 21. I2C Readback Register Settings Following Conversion Commands COMMAND X = panel setup Y = panel setup Z1 = panel setup Z2 = panel setup X, Y = combined command X, Y, Z1 = combined command X, Y, Z1, Z2 = combined command AUX = conversion X = measurement Y = measurement Z1 = measurement Z2 = measurement READBACK REGISTER LOCATION 52h 54h 56h 58h 52h 52h 52h 5Ah 52h 54h 56h 58h X = MSB Y = MSB Z1 = MSB Z2 = MSB X = MSB X = MSB X = MSB AUX = MSB X = MSB Y = MSB Z1 = MSB Z2 = MSB DESCRIPTION ______________________________________________________________________________________ 45 Low-Power, Ultra-Small Resistive Touch-Screen Controllers with I2C/SPI Interface MAX11800–MAX11803 Panel Setup and Measurement Commands TSC conversion commands are only to be used in direct conversion mode (AUTO = 0). Conversion commands issued during autonomous mode are ignored. All panel setup and measurement operations are automated when in autonomous mode (AUTO = 1). Commands must be issued in write mode to be executed. There are two types of commands: panel setup registers (0x6x) and measurement/conversion registers (0x7x). All measurement commands indicate that the ADC is used and the ADC can begin to power up once the 0x7x header has been recognized. All measurement commands modify the target data register upon the conclusion of the measurement command. The CONT bit impacts the setup of the panel and ADC following the command. For panel setup commands and combined commands, the user setting of this bit (R0) is ignored. For these commands, the internal assumption is shown in parentheses in Table 22. The CONT bit impacts the setup of the panel and/or ADC following the command (see command descriptions for details). For some commands, the user setting of this bit (R0) is ignored; for these commands the internal assumption is shown in parentheses in Tables 8 and 22. By definition, panel setup and measurement commands are NOT pairable in write mode as each command modifies the panel setting both during the command and after it (based on conversion executions and CONT bit settings). Table 22. Measurement Commands HEX 7xh 7xh 7xh 7xh 7xh 7xh 7xh 7xh R6 1 1 1 1 1 1 1 1 R5 1 1 1 1 1 1 1 1 R4 1 1 1 1 1 1 1 1 R3 0 0 0 0 1 1 1 1 R2 0 0 1 1 0 0 1 1 R1 0 1 0 1 0 1 0 1 R0 (0) (0) (0) (0) CONT CONT CONT CONT ACCESS Write Write Write Write Write Write Write Write PAIRABLE No No No No No No No No COMMAND LENGTH 8 8 8 8 8 8 8 8 OPERATION X, Y = combined measurement X, Y, Z1 = combined measurement X, Y, Z1, Z2 = combined measurement AUX = measurement X = measurement Y = measurement Z1 = measurement Z2 = measurement 46 ______________________________________________________________________________________ Low-Power, Ultra-Small Resistive Touch-Screen Controllers with I2C/SPI Interface User Configuration Registers General Status Register (0x00) (Read Only) BIT 7 NAME DEFAULT ADC_BUSY 0 BIT 6 LPM 0 BIT 5 TDM 0 BIT 4 SCAN 0 BIT 3 FIFO_OVR 0 BIT 2 FIFO_INT 0 BIT 1 EDGE_INT 0 BIT 0 CONT_INT 0 MAX11800–MAX11803 BIT 7 NAME ADC_BUSY 0: ADC is not in ACQ or CONV state 1: ADC is in ACQ or CONV state This is for INTERNAL TEST only DESCRIPTION 6 5 LPM TDM 0: Device is not in LPM or standby mode 1: Device is in LPM or standby mode 0: Device is not in TDM 1: Device is in TDM 0: No scan or measurement in progress 1: Scan or measurement in progress Also indicates presence of a continuous touch in autonomous mode 0: FIFO overflow has not occurred (MAX11800/MAX11801) 1: FIFO has overflowed since last readback operation Enabled only if AUTO = 1 0: No unread data in FIFO (MAX11800/MAX11801) 1: New data available in FIFO Enabled only if AUTO = 1 0: No touch event in progress 1: Touch event in progress (cleared on ETAG = 10) Enabled only if AUTO = 0 and EDGE_IRQ = 1 0: No touch present 1: Touch present (or conversion in progress) Enabled only if AUTO = 0 and EDGE_IRQ = 0 4 SCAN 3 FIFO_OVR 2 FIFO_INT 1 EDGE_INT 0 CONT_INT ______________________________________________________________________________________ 47 Low-Power, Ultra-Small Resistive Touch-Screen Controllers with I2C/SPI Interface MAX11800–MAX11803 General Configuration Register (0x01) BIT 7 NAME D EFAULT BIT 7 RT_SEL RT_SEL 1 NAME BIT 6 HOLD_DO 1 BIT 5 PU_IRQ 1 BIT 4 ODN_IRQ 1 BIT 3 MASK_IRQ 0 BIT 2 EDGE_IRQ 0 BIT 1 0 BIT 0 0 EDGE_TIME[1:0] DESCRIPTION 0: 50k touch-detection pullup resistance 1: 100k t ouch-detection pullup resistance (panel setting––not to be confused with internal TIRQ pullup) 0: DOUT internal bus holder disabled 1: DOUT internal bus holder enabled (applicable to SPI version only) 0: Disable IRQ internal pullup resistance 1: Enable IRQ internal pullup resistance (open-drain mode only: ODN_IRQ also high) 0: TIRQ i s CMOS buffered output 1: TIRQ i s open-drain nMOS output 0: Enable TIRQ output 1: Mask/disable TIRQ output (force high or high impedance) 0: Use continuous interrupt with direct conversion mode 1: Use edge interrupt with direct conversion mode TIRQ low time for edge interrupt mode only 00: 4 x (2MHz oscillator clock period) = 2μs 01: 16 x (2MHz oscillator clock period) = 8μs 10: 64 x (2MHz oscillator clock period) = 32μs 11: 128 x (2MHz oscillator clock period) = 128μs 6 HOLD_DO 5 PU_IRQ 4 3 2 ODN_IRQ MASK_IRQ EDGE_IRQ 1:0 EDGE_TIME[1:0] Measurement Resolution Configuration Register (0x02) BIT 7 NAME DEFAULT BIT — 0 NAME BIT 6 — 0 BIT 5 — 0 BIT 4 PWR_SAV 0 BIT 3 RESX 0 BIT 2 RESY 0 BIT 1 RESZ1 0 BIT 0 RESZ2 0 4 PWR_SAV 3:0 RES_ DESCRIPTION 0: Internal ADC runs at normal power 1: Internal ADC runs at reduced power and resolution This mode does limit the effective ADC resolution: 12-bit conversions may be reduced to 10-bit accuracy 8-bit conversions should not be impacted. Resolution for X, Y, Z1, or Z2 measurements 0: 12-bit conversion (see the PWR_SAV description in this table) 1: 8-bit conversion 48 ______________________________________________________________________________________ Low-Power, Ultra-Small Resistive Touch-Screen Controllers with I2C/SPI Interface MAX11800–MAX11803 Measurement Averaging Configuration Register (0x03)* BIT 7 NAME DEFAULT BIT 7:6 0 NAME AVG_X[1:0] BIT 6 0 BIT 5 0 BIT 4 0 BIT 3 0 BIT 2 0 BIT 1 0 BIT 0 0 AVG_X[1:0] AVG_Y[1:0] AVG_Z1[1:0] AVG_Z2[1:0] DESCRIPTION Averaging sample depth for X, Y, Z1, or Z2 measurements If AVG_FLT = 0 (see the Operating Mode Configuration Register (0x0B) section) 00: Single sample, no averaging 01: Take four samples, average two median samples 10: Take eight samples, average four median samples 11: Take 16 samples, average eight median samples If AVG_FLT = 1 (see the Operating Mode Configuration Register (0x0B) section) 00: Single sample, no averaging 01: Take four samples, average all samples 10: Take eight samples, average all samples 11: Take 16 samples, average all samples 5:4 AVG_Y[1:0] 3:2 AVG_Z1[1:0] 1:0 AVG_Z2[1:0] *The settings can be enabled and disabled through settings in the operating mode configuration register (0x0B), allowing for dynamic configuration of averaging modes depending on operating mode. ADC Sampling Time Configuration Register (0x04)* BIT 7 NAME DEFAULT BIT 7:6 5:4 3:2 1:0 0 NAME T_SAMPLE_X[1:0] T_SAMPLE_Y[1:0] T_SAMPLE_Z1[1:0] T_SAMPLE_Z2[1:0] BIT 6 0 BIT 5 0 BIT 4 0 BIT 3 0 BIT 2 0 BIT 1 0 BIT 0 0 T_SAMPLE_X[1:0] T_SAMPLE_Y[1:0] T_SAMPLE_Z1[1:0] T_SAMPLE_Z2[1:0] DESCRIPTION Sampling time for X, Y, Z1 or Z2 measurements 00: 4 x (2MHz oscillator clock period) = 2μs 01: 16 x (2MHz oscillator clock period) = 8μs 10: 64 x (2MHz oscillator clock period) = 32μs 11: 256 x (2MHz oscillator clock period) = 128μs *Time ADC spends sampling panel before starting conversion process. This time plus the ADC conversion time determines the sampling rate within averaging operations. Be sure to allow adequate time to settle the ADC capacitors given the panel effective source resistance. ______________________________________________________________________________________ 49 Low-Power, Ultra-Small Resistive Touch-Screen Controllers with I2C/SPI Interface MAX11800–MAX11803 Panel Setup Timing Configuration Register (0x05) BIT 7 NAME DEFAULT BIT 0 NAME 0 BIT 6 BIT 5 0 BIT 4 0 BIT 3 0 BIT 2 0 BIT 1 0 BIT 0 0 PSUXY[3:0] PSUZ[3:0] 7:4 PSUXY[3:0] 3:0 PSUZ[3:0] DESCRIPTION X, Y panel setup times (position measurements) 0000: 0μs 1000: 1ms 0001: 20μs 1001: 2ms 0010: 50μs 1010: 5ms 0011: 80μs 1011: 10ms 0100: 100μs 1100: 20ms 0101: 200μs 1101: 50ms 0110: 500μs 1110: 100ms 0111: 800μs 1111: 200ms Z panel setup times (pressure measurements) PSUZ[3:0] has the same range as PSUXY[3:0] above. Note: These settings apply to measurement commands, combined commands, and autonomous conversion mode measurements and provide time for the panel to settle prior to beginning measurements. During these periods, the panel is set up, but the ADC remains powered down. Users with low-impedance/fast settling panels should use setting 0000 (skip mode) if their panel can be settled during the required 10μs minimum delayed conversion time (see the Delayed Conversion Configuration Register (0x06) section). Delayed Conversion Configuration Register (0x06) BIT 7 NAME DEFAULT BIT 0 NAME BIT 6 0 BIT 5 0 BIT 4 0 BIT 3 0 BIT 2 0 BIT 1 0 BIT 0 0 D_CV_XY[3:0] D_CV_Z[3:0] 7:4 D_CV_XY[3:0] DESCRIPTION X, Y panel plus ADC setup times (position measurements) 0000: 10μs 1000: 1ms 0001: 20μs 1001: 2ms 0010: 50μs 1010: 5ms 0011: 80μs 1011: 10ms 0100: 100μs 1100: 20ms 0101: 200μs 1101: 50ms 0110: 500μs 1110: 100ms 0111: 800μs 1111: 200ms Z panel plus ADC setup times (pressure measurements) D_CV_Z[3:0] has the same range as D_CV_XY[3:0] above. 3:0 D_CV_Z[3:0] Note: These settings apply to measurement commands, combined commands, and autonomous conversion mode measurements and provide time for the panel and ADC to settle prior to beginning measurements. During these periods, the panel is set up and the ADC is powered up. In general, users with long panel settling requirements should minimize time in this mode, using increased panel setup times instead to save ADC power. 50 ______________________________________________________________________________________ Low-Power, Ultra-Small Resistive Touch-Screen Controllers with I2C/SPI Interface MAX11800–MAX11803 Touch-Detect Pullup Timing Configuration Register (0x07) BIT 7 NAME DEFAULT BIT 0 NAME Rough pullup time (tPUR) 0000: 2μs* 1000: 1ms 0001: 2μs 1001: 2ms 0010: 4μs 1010: 5ms 0011: 8μs 1011: 10ms 0100: 10μs 1100: 20ms 0101: 50μs 1101: 50ms 0110: 100μs 1110: 100ms 0111: 500μs 1111: 200ms Fine pullup time (tPUF) 0000: 10μs 1000: 1ms 0001: 20μs 1001: 2ms 0010: 50μs 1010: 5ms 0011: 80μs 1011: 10ms 0100: 100μs 1100: 20ms 0101: 200μs 1101: 50ms 0110: 500μs 1110: 100ms 0111: 800μs 1111: 200ms 0 BIT 6 PUR[3:0] 0 0 0 0 BIT 5 BIT 4 BIT 3 BIT 2 PUF[3:0] 0 0 BIT 1 BIT 0 DESCRIPTION 7:4 PUR[3:0] 3:0 PUF[3:0] Note: These settings apply to the end of all measurement and combined commands and are required for proper data tagging and interrupt management. The exception is direct conversion commands with CONT = 1. These commands do not enter PUR/PUF intervals for the purpose of data tagging. *While 2μs is the minimum PUR interval listed, for this setting, the XPSW is not engaged, allowing for minimal power operation (essentially adding 2μs to the PUF time). Autonomous Mode Timing Configuration Register (0x08) (MAX11800/MAX11801) BIT 7 NAME DEFAULT BIT 0 NAME 0 BIT 6 BIT 5 0 BIT 4 0 BIT 3 0 BIT 2 0 BIT 1 0 BIT 0 0 TINIT[3:0] SCANP[3:0] 7:4 TINIT[3:0] 3:0 SCANP[3:0] DESCRIPTION Initial period (time between touch and initial scan block, tINIT) 0000: 10μs 1000: 1ms 0001: 20μs 1001: 2ms 0010: 50μs 1010: 5ms 0011: 80μs 1011: 10ms 0100: 100μs 1100: 20ms 0101: 200μs 1101: 50ms 0110: 500μs 1110: 100ms 0111: 800μs 1111: 200ms Scan period (time between successive scan blocks, tSP) SCANP[3:0] has the same range as TINIT[3:0] above. Note: These settings apply in autonomous conversion mode only. ______________________________________________________________________________________ 51 Low-Power, Ultra-Small Resistive Touch-Screen Controllers with I2C/SPI Interface MAX11800–MAX11803 Aperture Configuration Register (0x09) (MAX11800/MAX11801) BIT 7 NAME DEFAULT 0 0 BIT 6 BIT 5 BIT 4 BIT 3 BIT 2 BIT 1 BIT 0 APRX[3:0] 0 0 0 0 APRY[3:0] 0 0 BIT NAME DESCRIPTION ±ΔX for aperture checking 0000 = 2-1 LSB = aperture checking disabled 0001 = 2(1-1) LSB = ±1 LSB 0010 = 2(2-1) LSB = ±2 LSB 0011 = 2(3-1) LSB = ±4 LSB 7:4 APRX[3:0] . . . 1001 = 2(9-1) LSB = ±256 LSB 1010 = 2(10-1) LSB = ±512 LSB 1011 = 2(11-1) LSB = ±1024 LSB 1100 = 2(12-1) LSB = ±2048 LSB 1101 to 1111 = aperture checking disabled 3:0 APRY[3:0] ±ΔY for aperture checking APRY[3:0] has the same range as APRX[3:0] above. Note: These aperture settings apply in autonomous conversion mode only and control whether data meets the criteria for logging into the FIFO. 52 ______________________________________________________________________________________ Low-Power, Ultra-Small Resistive Touch-Screen Controllers with I2C/SPI Interface MAX11800–MAX11803 Auxiliary Measurement Configuration Register (0x0A) BIT 7 NAME D EFAULT BIT 0 NAME Delay initial auxiliary conversion 000: 10μs 001: 100μs 010: 500μs 011: 1ms 100: 5ms 101: 10ms 110: 50ms 111: 100ms Sampling time for auxiliary measurements 00: 4 x (2MHz oscillator clock period) = 2μs 01: 16 x (2MHz oscillator clock period) = 8μs 10: 64 x (2MHz oscillator clock period) = 32μs 11: 256 x (2MHz oscillator clock period) = 128μs Averaging sample depth for auxiliary measurements If AVG_FLT = 0 (see the Operating Mode Configuration Register (0x0B) section) 00: Single sample, no averaging 01: Take four samples, average two median samples 10: Take eight samples, average four median samples 11: Take 16 samples, average eight median samples If AVG_FLT = 1 (see the Operating Mode Configuration Register (0x0B) section) 00: Single sample, no averaging 01: Take four samples, average all samples 10: Take eight samples, average all samples 11: Take 16 samples, average all samples Resolution for auxiliary measurements 0: 12-bit conversion (see the description of PWR_SAV in the Measurement Resolution Configuration Register (0x02) section) 1: 8-bit conversion BIT 6 D _CV_A[3:0] 0 0 BIT 5 BIT 4 0 BIT 3 0 BIT 2 0 BIT 1 0 BIT 0 RESA 0 T_SAMPLE_A[1:0] AVGA[1:0] DESCRIPTION 7:5 D_CV_A[3:0] 4:3 T_SAMPLE_A[1:0] 2:1 AVGA[1:0] 0 RESA Note: A delimiter refers to the auxiliary input (AUX). Auxiliary measurements can only be requested in direct conversion modes. ______________________________________________________________________________________ 53 Low-Power, Ultra-Small Resistive Touch-Screen Controllers with I2C/SPI Interface MAX11800–MAX11803 Operating Mode Configuration Register (0x0B) BIT 7 NAME D EFAULT BIT 7 PWRDN PWRDN 1 NAME 0 BIT 6 BIT 5 0 BIT 4 APER 0 BIT 3 AVG_FLT 0 BIT 2 EN_AVG_XY 0 BIT 1 EN_AVG_Z 0 0 BIT 0 AMODE[1:0] DESCRIPTION 0: Device is powered up and operational in either a direct or autonomous conversion mode (see AMODE[1:0] below). 1: Device is powered down, OTP is held in reset 00: Direct conversion mode (AUTO = 0) (MAX11800/MAX11801) 01: Autonomous X and Y scan (AUTO = 1) 10: Autonomous X, Y, Z1 scan (AUTO = 1) 11: Autonomous X, Y, Z1, Z2 scan (AUTO = 1) 0: Disregard aperture criteria (MAX11800/MAX11801) 1: Enable aperture criteria (spatial filter) (applies to autonomous modes only) 0: Use median averaging filters (ignore outliers) 1: Use straight averaging filters 0: Disable (X, Y) position averaging in selected mode 1: Enable (X, Y) position averaging in selected mode 0: Disable (Z1, Z2) pressure averaging in selected mode 1: Enable (Z1, Z2) pressure averaging in selected mode Reserved bit. 6:5 AMODE[1:0] 4 APER 3 2 1 0 AVG_FLT EN_AVG_XY EN_AVG_Z RESERVED *Any write access to 0x0B initiates an internal reset pulse. This pulse clears the FIFO and all measurement memories. 54 ______________________________________________________________________________________ Low-Power, Ultra-Small Resistive Touch-Screen Controllers with I2C/SPI Interface MAX11800/MAX11802 Typical Operating Circuit VDD MAX11800–MAX11803 1μF 0.1μF X+ Y+ VDD TIRQ GPIO DIN DOUT HOST PROCESSOR MAX11800 MAX11802 X- CLK CLK DOUT DIN CS TOUCH SCREEN YAUX INPUT AUX GND CS MAX11801/MAX11803 Typical Operating Circuit VDD 1μF 0.1μF 1.2kΩ 1.2kΩ OPTIONAL X+ Y+ VDD TIRQ GPIO SDA SDA HOST PROCESSOR MAX11801 MAX11803 X- SCL SCL A0 A0 A1 TOUCH SCREEN YAUX INPUT AUX GND A1 ______________________________________________________________________________________ 55 Low-Power, Ultra-Small Resistive Touch-Screen Controllers with I2C/SPI Interface MAX11800–MAX11803 Pin Configurations TOP VIEW CS 9 CLK 8 DIN 7 A DOUT 10 6 TIRQ B CLK *EP 4 XC DIN 1 X+ 2 VDD 3 GND TIRQ YXDOUT GND VDD CS AUX Y+ X+ MAX11800/MAX11802 1 2 3 4 + AUX 11 MAX11800 MAX11802 + 5 Y- Y+ 12 WLP TQFN A0 9 SCL 8 SDA 1 7 A A1 10 6 TIRQ A0 B SCL *EP 4 XC SDA 1 X+ 2 VDD 3 GND TIRQ YXA1 GND VDD AUX Y+ X+ MAX11801/MAX11803 2 3 4 + AUX 11 MAX11801 MAX11803 + 5 Y- Y+ 12 WLP TQFN *EXPOSED PAD. Chip Information PROCESS: CMOS Package Information For the latest package outline information and land patterns, go to www.maxim-ic.com/packages. Note that a “+”, “#”, or “-” in the package code indicates RoHS status only. Package drawings may show a different suffix character, but the drawing pertains to the package regardless of RoHS status. PACKAGE TYPE 12 TQFN 12 WLP PACKAGE CODE T1244+4 W121A2-1 DOCUMENT NO. 21-0139 21-0009 56 ______________________________________________________________________________________ Low-Power, Ultra-Small Resistive Touch-Screen Controllers with I2C/SPI Interface Revision History REVISION NUMBER 0 REVISION DATE 7/09 Initial release. Removed future status from the WLP packages in the Ordering Information t able. 1 11/09 Added a new Note 1 about the WLP package to the Absolute Maximum Ratings section. Corrected the pin names for the WLP packages in the P in Description table and Pin Configurations. 2 3/10 Added “Soldering Temperature (reflow) at +260°C.” in the Absolute Maximum Ratings section. DESCRIPTION PAGES CHANGED — 1 8 14, 56 8 MAX11800–MAX11803 Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are implied. Maxim reserves the right to change the circuitry and specifications without notice at any time. Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600 ____________________ 57 © 2010 Maxim Integrated Products Maxim is a registered trademark of Maxim Integrated Products, Inc.