MAX1512

19-2911 Rev 2; 8/04 KIT ATION EVALU ILABLE AVA EEPROM-Programmable TFT VCOM Calibrator General Description The MAX1512 is a programmable VCOM-adjustment solution for thin-film transistor (TFT) liquid-crystal displays (LCDs). The MAX1512 simplifies the labor-intensive VCOM-adjustment process and replaces mechanical potentiometers, which significantly reduces labor costs, increases reliability, and enables automation. The MAX1512 attaches to an external resistive voltagedivider and sinks a programmable current to set the VCOM voltage level. An internal 7-bit digital-to-analog converter (DAC) controls the sink current. The DAC is ratiometric relative to AVDD and is guaranteed to be monotonic over all operating conditions. This VCOM calibrator IC includes an EEPROM to store the desired VCOM voltage level. The EEPROM can be programmed repeatedly, giving TFT LCD manufacturers the flexibility to calibrate the display panel as many times as the manufacturing process requires. The IC features a single-wire interface between the LCD panel and the programming circuit. The singlewire interface delivers both programming power and DAC-adjustment commands to minimize changes to panel connectors and production equipment. The MAX1512 is available in an 8-pin 3mm x 3mm TDFN package. A complete evaluation kit is available to simplify evaluation and production development. Features ♦ 7-Bit Adjustable Sink-Current Output ♦ Resistor-Adjustable Full-Scale Range ♦ Guaranteed Monotonic Output Over Operating Range ♦ Single-Wire Adjustment and Programming* ♦ EEPROM Stores VCOM Setting ♦ Interface Enable/Disable Control (CE) ♦ 2.6V to 3.6V Logic Supply-Voltage Operating Range (VDD) ♦ 4.5V to 20V Analog Supply-Voltage Range (VAVDD) ♦ VDD UVLO Protection ♦ 8-Pin 3mm x 3mm TDFN (0.8mm max) MAX1512 Ordering Information PART MAX1512ETA TEMP RANGE -40°C to +85°C PIN-PACKAGE 8 TDFN 3mm x 3mm Applications LCD Panels Notebook Computers Monitors LCD TVs Typical Operating Circuit VDD Pin Configuration AVDD VDD TOP VIEW OUT AVDD N.C. GND 1 2 3 4 8 SET CE CTL VDD CE AVDD R1 MAX1512 7 6 5 MAX1512 OUT VCOM R2 CTL GND SET RSET TDFN *Patent Pending. ________________________________________________________________ Maxim Integrated Products 1 For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct! at 1-888-629-4642, or visit Maxim’s website at www.maxim-ic.com. EEPROM-Programmable TFT VCOM Calibrator MAX1512 ABSOLUTE MAXIMUM RATINGS VDD, SET, CE to GND...............................................-0.3V to +4V OUT to GND ...........................................................-0.3V to +14V AVDD to GND.........................................................-0.3V to +24V CTL to GND ............................................................-0.3V to +16V Continuous Power Dissipation (TA = +70°C) ............................... 8-Pin Thin QFN 3mm x 3mm (derate 24.4mW/°C above +70°C).............................................................1951mW Operating Temperature Range ...........................-40°C to +85°C Junction Temperature ......................................................+150°C Storage Temperature Range .............................-65°C to +160°C Lead Temperature (soldering, 10s) .................................+300°C 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 (Circuit of Figure 1, VDD = 3V, VAVDD = 10V, VOUT = 5V, RSET = 30.1kΩ, TA = 0°C to +85°C, unless otherwise noted. Typical values are at TA = +25°C.) (Note 1) PARAMETER SINK-CURRENT ADJUSTMENT SET Voltage Resolution SET Differential Nonlinearity SET Zero-Scale Error SET Full-Scale Error SET Current SET External Resistance (Note 2) VSET / VAVDD Voltage Ratio VSET / VAVDD Factory Set Voltage Ratio VDD SUPPLY VDD Supply Range VDD Supply Current VDD Power-On Reset Threshold VDD Power-On Reset Hysteresis CONTROL AND PROGRAMMING CE Input Low Voltage CE Input High Voltage CE Startup Time CTL High Voltage CTL Float Voltage CTL Low Voltage CTL Rejected Pulse Width CTL Minimum Pulse Width CTL Minimum Time Between Pulses CTL Input Current CTL = GND CTL = VDD -10 10 2.6V < VDD < 3.6V 2.6V < VDD < 3.6V (Note 3) 2.6V < VDD < 3.6V 2.6V < VDD < 3.6V 2.6V < VDD < 3.6V 0.70 x VDD 0.40 x VDD 0.20 x VDD 20 200 10 1.6 1 0.82 x VDD 0.62 x VDD 0.32 x VDD 0.4 V V ms V V V µs µs µs µA VDD IDD CE = VDD CE = GND Rising edge Falling edge 2.2 2.1 2.6 32 12 2.5 2.4 100 3.6 55 20 2.7 2.6 V µA V mV ISET RSET To GND, VAVDD = 20V To GND, VAVDD = 4.5V DAC full scale 0.024 10 2.25 0.05 0.025 0.026 Guaranteed monotonic 7 -1 -1 -12 +1 +1 +2 +12 120 200 45.00 Bits LSB LSB LSB µA kΩ V/V V/V SYMBOL CONDITIONS MIN TYP MAX UNITS 2 _______________________________________________________________________________________ EEPROM-Programmable TFT VCOM Calibrator ELECTRICAL CHARACTERISTICS (continued) (Circuit of Figure 1, VDD = 3V, VAVDD = 10V, VOUT = 5V, RSET = 30.1kΩ, TA = 0°C to +85°C, unless otherwise noted. Typical values are at TA = +25°C.) (Note 1) CTL Input Current µA CTL = VDD 10 PARAMETER CTL EEPROM Program Voltage OUTPUT VOLTAGE OUT Leakage Current OUT Settling Time VOUT Voltage Range AVDD SUPPLY VAVDD Supply Range VAVDD 4.5 20.0 V VOUT VDD = 2.1V To ±0.5 LSB error band VSET + 0.5V 1 20 13 nA µs V SYMBOL VPP (Note 3) CONDITIONS MIN 15.25 TYP 15.5 MAX 15.75 UNITS V MAX1512 ELECTRICAL CHARACTERISTICS (VDD = 3V, VAVDD = 10V, VOUT = 5V, RSET = 30.1kΩ, TA = -40°C to +85°C, unless otherwise noted.) (Note 1) PARAMETER SINK-CURRENT ADJUSTMENT SET Differential Nonlinearity SET Zero-Scale Error SET Full-Scale Error SET Current SET External Resistance (Note 2) VDD SUPPLY VDD Supply Range VDD Supply Current VDD Power-On Reset Threshold CONTROL AND PROGRAMMING CE Input Low Voltage CE Input High Voltage AVDD SUPPLY VAVDD Supply Range VAVDD 4.5 20.0 V AVDD Operating Current IAVDD VAVDD = 20V 20 µA Note 1: Limits are 100% production tested at TA = +25°C. Limits over the operating temperature range are guaranteed through correlation using standard quality control (SQC) methods. Note 2: SET external resistor range is verified at DAC full scale. Note 3: Guaranteed by design. Not production tested. 2.6V < VDD < 3.6V 2.6V < VDD < 3.6V 1.6 0.4 V V VDD IDD CE = VDD CE = GND Rising edge Falling edge 2.2 2.1 2.6 3.6 55 20 2.7 2.6 V µA V ISET RSET To GND, VAVDD = 20V To GND, VAVDD = 4.5V 10 2.25 Guaranteed monotonic -1 -1 -12 +1 +2 +12 120 200 45.00 LSB LSB LSB µA kΩ SYMBOL CONDITIONS MIN TYP MAX UNITS _______________________________________________________________________________________ 3 EEPROM-Programmable TFT VCOM Calibrator MAX1512 Typical Operating Characteristics (Circuit of Figure 1, VDD = 3V, VAVDD = 10V, VOUT = 5V, RSET = 24.9kΩ, TA = +25°C, DAC half scale, unless otherwise noted.) VDD SUPPLY CURRENT vs. TEMPERATURE MAX1512 toc01 VDD SUPPLY CURRENT vs. VDD MAX1512 toc02 IOUT vs. RSET VAVDD = 20V 1000 MAX1512 toc03 33.2 33.0 VDD SUPPLY CURRENT (µA) 32.8 32.6 32.4 32.2 32.0 31.8 31.6 31.4 -40 40 CE = VDD 35 VDD SUPPLY CURRENT (µA) 30 25 20 15 RISING FALLING 10,000 CE = VDD = 3V IOUT (µA) 100 VAVDD = 4.5V 10 10 5 0 1 VDD = VOUT = 3V 0.1 2.2 2.4 2.6 2.8 3.0 3.2 3.4 3.6 0.1 1 10 RSET (kΩ) 100 1000 VDD (V) -20 0 20 40 60 80 TEMPERATURE (°C) IOUT SINK-CURRENT ERROR vs. VDD MAX1512 toc04 IOUT SINK-CURRENT ERROR vs. VAVDD 3.00 2.95 2.90 2.85 2.80 2.75 2.70 MAX1512 toc05 2.855 IOUT SINK-CURRENT ERROR (LSB) 2.850 2.845 2.840 2.835 2.830 2.825 2.820 2.6 2.8 3.0 3.2 3.4 3.05 IOUT SINK-CURRENT ERROR (LSB) 3.6 4.5 6.5 8.5 10.5 12.5 14.5 16.5 18.5 VAVDD (V) VDD (V) IOUT SINK-CURRENT ERROR vs. VOUT MAX1512 toc06 IOUT SINK-CURRENT ERROR vs. TEMPERATURE MAX1512 toc07 2.840 IOUT SINK-CURRENT ERROR (LSB) 3.0 IOUT SINK-CURRENT ERROR (LSB) 2.9 2.835 2.8 2.830 0 0.5 1.0 VOUT (V) 1.5 2.0 2.7 -40 -20 0 20 40 60 80 TEMPERATURE (°C) 4 _______________________________________________________________________________________ EEPROM-Programmable TFT VCOM Calibrator MAX1512 Typical Operating Characteristics (continued) (Circuit of Figure 1, VDD = 3V, VAVDD = 10V, VOUT = 5V, RSET = 24.9kΩ, TA = +25°C, DAC half scale, unless otherwise noted.) INTEGRAL NONLINEARITY vs. DAC SETTING MAX1512 toc09 MAX1512 toc08 TOTAL UNADJUSTED ERROR vs. DAC SETTING 7 RSET = 25kΩ TOTAL UNADJUSTED ERROR (LSB) 6 5 4 3 2 1 0 0 16 32 48 64 80 96 112 128 DAC SETTING RSET = 100kΩ 1.0 0.8 INTEGRAL NON-LINEARITY (LSB) 0.6 0.4 0.2 0 -0.2 -0.4 -0.6 -0.8 -1.0 0 16 DIFFERENTIAL NONLINEARITY vs. DAC SETTING DIFFERENTIAL NON-LINEARITY (LSB) 0.8 0.6 0.4 0.2 0 -0.2 -0.4 -0.6 -0.8 -1.0 MAX1512 toc10 1.0 RSET = 100kΩ RSET = 25kΩ 32 48 64 80 96 112 128 0 16 32 48 64 80 96 112 128 DAC SETTING DAC SETTING AVDD POWER-UP RESPONSE MAX1512 toc11 VDD POWER-UP RESPONSE VAVDD 10V/div 0 COUT = 100pF MAX1512 toc12 COUT = 100pF 5V 4V VOUT VOUT 1V/div 10V VAVDD 0 0 VDD 2V/div 0 40µs/div 40µs/div 0 VDD 2V/div SINGLE LSB STEP-UP RESPONSE MAX1512 toc13 SINGLE LSB STEP-DOWN RESPONSE MAX1512 toc14 COUT = 100pF COUT = 100pF VOUT 5mV/div VOUT 5mV/div 2V VCTL 0 40µs/div 40µs/div 2V VCTL 0 _______________________________________________________________________________________ 5 EEPROM-Programmable TFT VCOM Calibrator MAX1512 Pin Description PIN 1 2 3 4 5 NAME OUT AVDD N.C. GND VDD FUNCTION Adjustable Sink-Current Output. OUT connects to the resistive voltage-divider between AVDD and GND that sets the VCOM voltage. IOUT lowers the divider voltage by an adjustable amount. See the SET pin description. High-Voltage Analog Supply. Connects to the panel source-driver supply rail. No Connect. Not internally connected. Ground Supply Input. +2.6V to +3.6V input range. VCOM Adjustment and EEPROM Programming Control. CTL sets the internal DAC code and programs the EEPROM. A pulse-control method is used to adjust the VCOM level. See the VCOM Adjustment (CTL) section. To program the DAC setting into the EEPROM as the power-on default, drive CTL to the EEPROM programming voltage using the correct timing and voltage ramp rates. See the EEPROM Programming (CTL) section. Control Interface Enable. Connect CE to VDD to enable the CTL input. Connect CE to GND to disable the CTL input and reduce the supply current. Full-Scale Sink-Current Adjustment Input. Connect a resistor, RSET, from SET to GND to set the full-scale adjustable sink current. The full-scale adjustable sink current is equal to: 6 CTL 7 CE 8 SET  VAVDD   20 × R   SET  IOUT is equal to the current through RSET. Detailed Description The MAX1512 is a solid-state alternative to mechanical potentiometers used for adjusting the LCD backplane voltage (VCOM) in TFT LCD displays. The MAX1512 attaches to an external resistive voltage-divider and sinks a programmable current (IOUT), which sets the VCOM level (Figure 1). An internal 7-bit DAC controls the sink current and allows the user to increase or decrease the VCOM level (Figure 2). The DAC is ratiometric relative to AVDD and is monotonic over all operating conditions. The user can store the DAC setting in an internal EEPROM. On power-up, the EEPROM presets the DAC to the last stored setting. The single-wire interface between the LCD panel and the programming circuit adjusts the DAC, programs the EEPROM, and provides programming power. The resistive voltage-divider and the AVDD supply set the maximum value of VCOM. The MAX1512 sinks current from the voltage-divider to reduce the VCOM level. The external resistor RSET sets the full-scale sink current and the minimum value of VCOM. VDD 3V AVDD 10V VDD CE AVDD R1 200kΩ MAX1512 OUT R2 245kΩ SET GND RSET 25kΩ VCOM 5V CTL Figure 1. Standard Application Circuit 6 _______________________________________________________________________________________ EEPROM-Programmable TFT VCOM Calibrator MAX1512 VDD AVDD VDD AVDD 19R CE CTL CTL CONTROL INTERFACE 7 R2 DAC R OUT VCOM R1 SET EEPROM 7 RSET MAX1512 GND Figure 2. Simplified Functional Diagram Setting the VCOM Adjustment Range (RSET) The external resistive voltage-divider sets the maximum value of the VCOM adjustment range. RSET sets the full-scale sink current, IOUT, which determines the minimum value of the VCOM adjustment range. Large RSET values increase resolution but decrease the VCOM adjustment range. Calculate R1, R2, and RSET using the following procedure: 1) Choose the maximum VCOM level (VMAX), the minimum VCOM level (V MIN), and the AVDD supply voltage (VAVDD). 2) Calculate the R1 / R2 ratio: R1 V ≅ AVDD - 1 R2 VMAX 3) Calculate the R1 / RSET ratio: R1 RSET ≅ 4) Choose RSET according to the limits shown in the Electrical Characteristics section and calculate the values for R1 and R2. 5) The resulting resolution is: Re solution = (VMAX -VMIN ) 127 A complete design example is given below: 1) VMAX = 5V, VMIN = 3V, VAVDD = 10V 2) 10 R1 ≅ - 1 =1 5 R2 R1 RSET = 20 × 3) (5 - 3) = 8 5 (VMAX -VMIN ) VMAX × 20 4) If R SET = 24.9k Ω , then R1 = 200k Ω and R2 = 200kΩ 5) Resolution = 15.75mV _______________________________________________________________________________________ 7 EEPROM-Programmable TFT VCOM Calibrator MAX1512 MECHANICAL POTENTIOMETER AVDD MAX1512 EQUIVALENT CIRCUIT Ra AVDD Rb VCOM MAX1512 Rc OUT SET R1 = Ra R2 = Rb + Rc Ra × (Rb + Rc) RSET = 20 × Rb RSET AVDD R1 R2 VCOM Figure 3. Replacement of Mechanical/Potentiometer Circuit MECHANICAL POTENTIOMETER AVDD MAX1512 EQUIVALENT CIRCUIT Rd AVDD Re VCOM MAX1512 Rf R1 = Rd R2 = Rf Rd × (Rd + Re + Rf) RSET = 20 × Re OUT SET RSET AVDD R1 R2 VCOM Figure 4. Replacement of Mechanical/Potentiometer Circuit Translating Existing Potentiometer Circuits Existing VCOM adjustment circuits using conventional mechanical potentiometers can be translated into MAX1512 circuits. Figures 3 and 4 show two common adjustment circuits and their equivalent MAX1512 circuits. Interface Enable/Disable (CE) The MAX1512 control interface can be disabled to reduce the VDD supply current. Connect CE to GND to reduce the typical supply current from 32µA to 12µA. Connect CE to VDD to enable the control interface. 8 _______________________________________________________________________________________ EEPROM-Programmable TFT VCOM Calibrator VDD CE PROGRAMMING CIRCUIT RCE MAX1512 The programming circuit in Figure 5 drives CE high to enable the CTL input when it is connected. When the programming circuit is not connected, CE is pulled low through resistor RCE, which disables the CTL input. The CTL input is relatively immune to noise and brief voltage transients. It can be safely left continuously enabled if higher supply current is acceptable. MAX1512 VCOM Adjustment (CTL) CTL GND Pulse CTL low for more than 200µs to increment the DAC setting, which increases the OUT sink current and lowers the VCOM level by 1 least-significant bit (LSB) (Figure 6). Similarly, pulse CTL high for more than 200µs to decrement the DAC setting, which decreases the OUT sink current and increases the VCOM level by 1 LSB. Figure 5. Optional Circuit to Drive CE >1ms >200µs >200µs >200µs >10µs >200µs