AK8973

ASAHI KASEI [AK8973] =Preliminary= AK8973 3-axis Electronic Compass 1. Features … 3-axis electronic compass IC … Optimal built-in electronic compass for mobile phones and handy terminals … High sensitivity Hall sensors are integrated. … Functions • Built-in 8-bit ADC • Built-in amplifier for sensor signal amplification • Built-in 8-bit DAC for sensor signal offset compensation • Built-in EEPROM for storing individual adjustment values • Built-in temperature sensor • 8-bit digital output • Serial interface: I2C bus interface (supporting the low-voltage specification) • Automatic power-down function • Interrupt function for measurement data ready • Built-in master clock oscillator … Operating temperatures: … Operating supply voltage: +2.5V to +3.6V … Low current consumption/measurement time: • Power-down: 0.2μA typ. • Magnetic sensor driving: 6.8mA/12.6ms … Package: 16-pin QFN package: MS0561-E-01 -30°C to +85°C 4.0mm×4.0mm×0.7mm -1- 2007/01 ASAHI KASEI [AK8973] 2. Overview AK8973 is a geomagnetism detection type electronic compass IC. The small package of AK8973 integrates magnetic sensors for detecting geomagnetism in the X-axis, Y-axis, and Z-axis, and arithmetic circuit for processing the signal from each sensor. AK8973 outputs four data in total as 8-bit digital values respectively: 3-axis magnetic sensor measured values and temperature sensor read value. By processing the magnetic sensor measured values with an external CPU, azimuth data can be obtained. By using AK8973 integrated into the system, a navigation system is achieved with reduced space in portable equipment such as PDA or mobile phone incorporating the GPS function. Specifically, AK8973 has the following features: (1) Due to the built-in 8-bit ADC and serial interface, geomagnetism of the X-axis, Y-axis, and Z-axis can be detected as digital data. (2) The serial interface corresponds to the I2C bus. (3) A dedicated power supply is used for the serial interface, so the low-voltage specification can also be supported by applying 1.85V. (4) Due to the built-in DAC for compensating the offset magnetic field, the position restraint with parts which generate the offset magnetic field such as speakers is reduced, and the degree of freedom about layout is expanded. Note 1) (5) An EEPROM for storing the individual adjustment values of sensor sensitivity is built-in. The adjustment values are stored in factory at the time of shipment from AKM. (6) The built-in temperature sensor as an accessory generates the 8-bit digital A/D-converted value. The temperature information is not used for azimuth calculation. (7) The major circuit blocks of AK8973 are activated by the measurement request command from the controller, and transit to the power-down mode automatically at the end of measurement. That characteristic realizes the low power consumption required for mobile phones. (8) The interrupt function for posting the completion of sensor signal measurement to the external CPU is built-in. (9) The master clock oscillator is built-in. It is unnecessary to supply the clock from the outside. Note 1) For AK8973, the offset magnetic field compensation range is approximately ±2.0mT (typical geomagnetism range is approximately 0.05mT). Depending on usage or required accuracy, use with the full-range is available. However, for the azimuth measurement by the mobile phones, it is important to regard the following in the design phase: the magnetic field intensity of offset magnetic field source (e.g. magnet of speaker) is not fully controlled, and the temperature characteristic dispersion is noted. With AK8973, it is recommended that the design be performed with the parts layout where the offset magnetic field of each measurement axis is ±0.8mT or less. MS0561-E-01 -2- 2007/01 ASAHI KASEI [AK8973] 3. Table of Contents 1. 2. 3. 4. Features ....................................................................................................................................1 Overview ...................................................................................................................................2 Table of Contents ......................................................................................................................3 Circuit Configuration ..................................................................................................................5 4.1. Block Diagram....................................................................................................................5 4.2. Block Function....................................................................................................................6 4.3. Pin Function .......................................................................................................................7 5. Overall Characteristics ..............................................................................................................8 5.1. Absolute Maximum Ratings................................................................................................8 5.2. Recommended Operating Conditions ................................................................................8 5.3. Electrical Characteristics ....................................................................................................8 5.3.1. DC Characteristics ......................................................................................................8 5.3.2. EEPROM Characteristics............................................................................................9 5.3.3. Analog Circuit Characteristics .....................................................................................9 5.4. Detailed Timing...................................................................................................................9 5.4.1. Various Timing.............................................................................................................9 5.4.2. I2C Bus Interface .......................................................................................................10 6. Functional Explanation ............................................................................................................ 11 6.1. Operation Modes.............................................................................................................. 11 6.2. Description of Each Operation Mode................................................................................12 6.2.1. Power-down Mode ....................................................................................................12 6.2.2. Sensor Measurement Mode ......................................................................................12 6.2.3. EEPROM Mode.........................................................................................................13 6.3. Interrupt Function based on INT Pin.................................................................................13 7. Serial Interface ........................................................................................................................14 7.1. Data Transfer....................................................................................................................14 7.1.1. Change of Data .........................................................................................................14 7.1.2. Start/Stop Condition ..................................................................................................14 7.1.3. Acknowledge.............................................................................................................15 7.1.4. Slave Address ...........................................................................................................15 7.2. WRITE Instruction ............................................................................................................16 7.3. READ Instruction..............................................................................................................17 7.3.1. Current Address READ .............................................................................................17 7.3.2. Random READ..........................................................................................................17 8. Registers .................................................................................................................................18 8.1. Description of Registers ...................................................................................................18 8.2. Register Map....................................................................................................................19 8.3. Detailed Description of Registers .....................................................................................20 8.3.1. ST: Status Register....................................................................................................20 8.3.2. TMPS: Temperature Sensor Data Register ...............................................................20 8.3.3. H1X, H1Y, H1Z: Sensor Data Register......................................................................21 8.3.4. MS1: Mode Setting Register 1 ..................................................................................21 8.3.5. HXDA, HYDA, HZDA: Magnetic Sensor DAC Setting Register.................................22 8.3.6. HXGA, HYGA, HZGA: Magnetic Sensor Gain Setting Register ................................23 9. EEPROM.................................................................................................................................24 9.1. Outline of the Function .....................................................................................................24 9.2. Operation Description.......................................................................................................25 9.2.1. READ Instruction.......................................................................................................25 9.2.1.1. Current Address READ ......................................................................................25 9.2.1.2. Random READ ..................................................................................................25 9.2.2. WRITE Instruction .....................................................................................................26 9.2.2.1. Byte-Write ..........................................................................................................26 9.3. Memory Map ....................................................................................................................27 10. Example of Recommended External Connection ....................................................................28 11. Package ..................................................................................................................................29 11.1. Marking ............................................................................................................................29 11.2. Pin Assignment ................................................................................................................29 MS0561-E-01 -3- 2007/01 ASAHI KASEI [AK8973] 11.3. Outline Dimensions ..........................................................................................................30 11.4. Recommended Foot Print Pattern ....................................................................................30 12. Relationship between the Magnetic Field and Output Code....................................................31 MS0561-E-01 -4- 2007/01 ASAHI KASEI [AK8973] 4. Circuit Configuration 4.1. Block Diagram HE-X Chopper SW Integrator Pre-AMP ADC S&H MUX HE-Y HE-Z DAC SCL T-sensor SDA HE-Drive Interface Logic &Register OSC CAD1 CAD0 RSTN INT Timing Logic Voltage Reference TST1 MS0561-E-01 TST2 -5- TST3 EEPROM VSS VID VDD 2007/01 ASAHI KASEI 4.2. [AK8973] Block Function Block HE-X, Y, Z MUX Chopper SW HE-Drive Pre-AMP DAC Integrator S&H ADC T-sensor OSC Interface Logic & Register Timing Logic EEPROM Function High sensitivity sensors included in the package Multiplexer for selecting one axis from the 3-axis magnetic sensor Performs chopping. Magnetic sensor drive circuit for constant-current driving of sensor Variable-gain differential amplifier used to amplify a magnetic sensor signal and to adjust sensitivity. Gain setting: 26.8dB min., increased in 0.4dB/step, 16 steps (4 bits) DAC for offset voltage compensation. Resolution: 8 bits Integrates and amplifies the Pre-AMP output signal. Sample-and-hold circuit Performs analog-to-digital conversion for the signal of each sensor. Resolution: 8 bits Temperature sensor: Outputs the voltage proportional to the temperature. Built-in oscillator Automatically oscillates the operation clock in the sensor measurement mode. Exchanges data with the external CPU. I2C bus interface using two pins, namely, SCL and SDA. Using two pins of CAD0 and CAD1, lower 2-bit of slave address can be specified. Completion of sensor signal measurement is posted to the external CPU via INT pin. The low-voltage specification can be supported by applying 1.85V to the VID pin. Generates a timing signal required for internal operation based on the OSC generated clock. Nonvolatile memory. Stores initial adjustment values of each sensor at the time of shipment from AKM. The I2C bus interface is supported. Accessible through the two pins of SCL and SDA. Do not write to the EEPROM in ordinary use. MS0561-E-01 -6- 2007/01 ASAHI KASEI 4.3. [AK8973] Pin Function Power supply system VID VID No. Pin name I/O 1 2 3 CAD0 CAD1 VID I I - 4 SDA I/O VID CMOS 5 SCL I VID CMOS 6 TST1 I/O - Analog 7 INT O VID CMOS 8 RSTN I VID CMOS 9 NC1 - - - 10 11 TST2 TST3 I/O I/O - Analog Analog 12 13 14 NC2 NC3 NC4 - - - 15 16 VDD VSS - MS0561-E-01 Type Function CMOS CMOS POWER Slave address 0 input pin Slave address 1 input pin Digital interface positive power supply pin. This pin is a positive power supply pin for the digital interface block. By connecting this pin to a 1.85V power supply, the low-voltage specification digital interface can be connected. Control data input/output pin Input: Schmidt trigger, Output: Open drain Control data clock input pin Input: Schmidt trigger Test pin In usual use, eliminate unnecessary wiring, separate this pin from other test pins, and keep this pin electrically nonconnected. Interrupt signal output pin This pin is used to post the measurement completion to the external CPU. Refer to 6.3. Reset pin This pin resets all the register values when "L" is applied. After turning the power on, be sure to apply "L". Nonconnected pin In usual use, eliminate unnecessary wiring, separate this pin from other test pins, and keep this pin electrically nonconnected. Test pin In usual use, eliminate unnecessary wiring, separate this pin from other test pins, and keep this pin electrically nonconnected. Nonconnected pin In usual use, eliminate unnecessary wiring, separate this pin from other test pins, and keep this pin electrically nonconnected. Power supply pin Ground pin POWER POWER -7- 2007/01 ASAHI KASEI [AK8973] 5. Overall Characteristics 5.1. Absolute Maximum Ratings VSS=0V Parameter Symbol Min. Max. Unit V+ -0.3 +6.5 Power supply voltage V (VDD, VID) VIN -0.3 (V+)+0.3 Input voltage V IIN Input current mA ±10 TST -40 +85 Storage temperature °C Note If the device is used in conditions exceeding these values, the device may be destroyed. Normal operations and EEPROM data are not guaranteed in such exceeding conditions. 5.2. Recommended Operating Conditions VSS=0V Parameter Remark Symbol Min. Typ. Ta -30 Operating temperature VDD 2.5 3.0 Power supply VDD pin voltage VID pin voltage VID 1.70 1.85 voltage Note When turning on/off the power, turn on/off VDD and VID at the same time. . 5.3. Max. +85 Unit °C 3.6 VDD V V Electrical Characteristics The following conditions apply unless otherwise noted: VDD=2.5V to 3.6V, VID=1.7V to VDD, Temperature range=-30°C to 85°C 5.3.1. DC Characteristics Parameter High level input voltage 1 Symbol VIH1 Low level input voltage 1 VIL1 High level input voltage 2 Low level input voltage 2 VIH2 VIL2 IIN Input current (Note 1) Hysteresis input voltage (Note 2) VHS High level output voltage 1 Low level output voltage 1 Low level output voltage 2 VOH1 VOL1 VOL2 (Note 3)(Note 4) Current consumption IDD1 Pin SCL SDA CAD0 CAD1 RSTN SCL SDA CAD0 CAD1 RSTN SCL SDA INT SDA Condition Min. 70%VID Typ. Max. Unit V 30%VID V 20%VID +10 V V μA 0.2 0.4 0.4 20%VID 5 V V V V V V μA 80%VID Vin=VSS or VID VID≥2V VID