Datasheet ADXL354, ADXL355 (Analog Devices) - 20

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ADXL354/ADXL355 Data Sheet THEORY OF OPERATION
The ADXL354 is a complete 3-axis, ultralow noise and ultrastable
ANALOG OUTPUT
offset MEMS accelerometer with outputs ratiometric to the analog Figure 57 shows the ADXL354 application circuit. The analog 1.8 V supply, V1P8ANA. The ADXL355 adds three high resolution outputs (XOUT, YOUT, and ZOUT) are ratiometric to the 1.8 V ADCs that use the analog 1.8 V supply as a reference to provide analog voltage from the V1P8ANA pin. V1P8ANA can be powered digital outputs insensitive to the supply voltage. The ADXL354B with an on-chip LDO that is powered from VSUPPLY. V1P8ANA can is pin selectable for ±2 g or ±4 g full scale, the ADXL354C is pin also be supplied externally by forcing VSUPPLY to VSS, which selectable for ±2 g or ±8 g full scale, and the ADXL355 is disables the LDO. Due to the ratiometric response, the analog programmable for ±2.048 g, ±4.096 g, and ±8.192 g full scale. output requires referencing to the V1P8ANA supply when The ADXL355 offers both SPI and I2C communications ports. digitizing to achieve the inherent noise and offset performance The micromachined, sensing elements are fully differential, of the ADXL354. The 0 g bias output is nominally equal to comprising the lateral x-axis and y-axis sensors and the vertical, V1P8ANA/2. The recommended option is to use the ADXL354 teeter totter z-axis sensors. The x-axis and y-axis sensors and with a ratiometric ADC (for example, the Analog Devices, Inc., the z-axis sensors go through separate signal paths that minimize AD7682) with V1P8ANA providing the voltage reference. This offset drift and noise. The signal path is fully differential, except configuration results in self cancellation of errors due to minor for a differential to single-ended conversion at the analog supply variations. outputs of the ADXL354. The ADXL354 outputs two forms of filtering: internal anti- The analog accelerometer outputs of the ADXL354 are ratiometric aliasing filtering with a cutoff frequency of approximately 1.5 kHz, to V1P8ANA; therefore, carefully digitize them correctly. The and external filtering. The external filter uses a fixed, on-chip, temperature sensor output is not ratiometric. The XOUT, YOUT, 32 kΩ resistance in series with each output in conjunction with and ZOUT analog outputs are filtered internally with an anti- the external capacitors to implement the low-pass filter antialiasing aliasing filter. These analog outputs also have an internal 32 kΩ and noise reduction prior to the external ADC. The antialias series resistor that can be used with an external capacitor to set filter cutoff frequency must be significantly higher than the the bandwidth of the output. desired signal bandwidth. If the antialias filter corner is too low, The ADXL355 includes antialias filters before and after the high ratiometricity can be degraded where the signal attenuation is resolution Σ-Δ ADC. User-selectable output data rates and filter different than the reference attenuation. corners are provided. The temperature sensor is digitized with a
T T T 2.25V TO 3.6V OU OU OU Z Y X
12-bit successive approximation register (SAR) ADC.
VDDIO (±4g , ±8g ) 14 13 12 GND ( ± 2g ) 0.1µF 1µF 1 11 V RANGE SUPPLY V 10 1P8ANA ADC VREF ST1 2 0.1µF 1µF ADXL354 V 9 SS ST2 3 V 8 1P8DIG TEMP 4 5 6 7 VDDIO (MEASUREMENT) O O Y GND (STANDBY) B DDI SSI V V ST 1µF 1µF 2.25V TO 3.6V
022 5-
0.1µF 0.1µF
420 1 Figure 57. ADXL354 Application Circuit Rev. 0 | Page 20 of 42 Document Outline FEATURES APPLICATIONS GENERAL DESCRIPTION FUNCTIONAL BLOCK DIAGRAMS TABLE OF CONTENTS REVISION HISTORY SPECIFICATIONS ANALOG OUTPUT FOR THE ADXL354 DIGITAL OUTPUT FOR THE ADXL355 SPI DIGITAL INTERFACE CHARACTERISTICS FOR THE ADXL355 I2C DIGITAL INTERFACE CHARACTERISTICS FOR THE ADXL355 ABSOLUTE MAXIMUM RATINGS THERMAL RESISTANCE ESD CAUTION PIN CONFIGURATIONS AND FUNCTION DESCRIPTIONS TYPICAL PERFORMANCE CHARACTERISTICS ROOT ALLAN VARIANCE (RAV) ADXL355 CHARACTERISTICS THEORY OF OPERATION ANALOG OUTPUT DIGITAL OUTPUT AXES OF ACCELERATION SENSITIVITY POWER SEQUENCING POWER SUPPLY DESCRIPTION VSUPPLY V1P8ANA V1P8DIG VDDIO OVERRANGE PROTECTION SELF TEST FILTER SERIAL COMMUNICATIONS SPI PROTOCOL I2C PROTOCOL READING ACCELERATION OR TEMPERATURE DATA FROM THE INTERFACE FIFO INTERRUPTS DATA_RDY DRDY PIN FIFO_FULL FIFO_OVR ACTIVITY NVM_BUSY EXTERNAL SYNCHRONIZATION AND INTERPOLATION EXT_SYNC = 00—No External Sync or Interpolation EXT_SYNC = 10—External Sync with Interpolation EXT_SYNC = 01—External Sync and External Clock ADXL355 REGISTER MAP REGISTER DEFINITIONS ANALOG DEVICES ID REGISTER Address: 0x00, Reset: 0xAD, Name: DEVID_AD ANALOG DEVICES MEMS ID REGISTER Address: 0x01, Reset: 0x1D, Name: DEVID_MST DEVICE ID REGISTER Address: 0x02, Reset: 0xED, Name: PARTID PRODUCT REVISION ID REGISTER Address: 0x03, Reset: 0x00, Name: REVID STATUS REGISTER Address: 0x04, Reset: 0x00, Name: STATUS FIFO ENTRIES REGISTER Address: 0x05, Reset: 0x00, Name: FIFO_ENTRIES TEMPERATURE DATA REGISTERS Address: 0x06, Reset: 0x00, Name: TEMP2 Address: 0x07, Reset: 0x00, Name: TEMP1 X-AXIS DATA REGISTERS Address: 0x08, Reset: 0x00, Name: XDATA3 Address: 0x09, Reset: 0x00, Name: XDATA2 Address: 0x0A, Reset: 0x00, Name: XDATA1 Y-AXIS DATA REGISTERS Address: 0x0B, Reset: 0x00, Name: YDATA3 Address: 0x0C, Reset: 0x00, Name: YDATA2 Address: 0x0D, Reset: 0x00, Name: YDATA1 Z-AXIS DATA REGISTERS Address: 0x0E, Reset: 0x00, Name: ZDATA3 Address: 0x0F, Reset: 0x00, Name: ZDATA2 Address: 0x10, Reset: 0x00, Name: ZDATA1 FIFO ACCESS REGISTER Address: 0x11, Reset: 0x00, Name: FIFO_DATA X-AXIS OFFSET TRIM REGISTERS Address: 0x1E, Reset: 0x00, Name: OFFSET_X_H Address: 0x1F, Reset: 0x00, Name: OFFSET_X_L Y-AXIS OFFSET TRIM REGISTERS Address: 0x20, Reset: 0x00, Name: OFFSET_Y_H Address: 0x21, Reset: 0x00, Name: OFFSET_Y_L Z-AXIS OFFSET TRIM REGISTERS Address: 0x22, Reset: 0x00, Name: OFFSET_Z_H Address: 0x23, Reset: 0x00, Name: OFFSET_Z_L ACTIVITY ENABLE REGISTER Address: 0x24, Reset: 0x00, Name: ACT_EN ACTIVITY THRESHOLD REGISTERS Address: 0x25, Reset: 0x00, Name: ACT_THRESH_H Address: 0x26, Reset: 0x00, Name: ACT_THRESH_L ACTIVITY COUNT REGISTER Address: 0x27, Reset: 0x01, Name: ACT_COUNT FILTER SETTINGS REGISTER Address: 0x28, Reset: 0x00, Name: Filter FIFO SAMPLES REGISTER Address: 0x29, Reset: 0x60, Name: FIFO_SAMPLES INTERRUPT PIN (INTx) FUNCTION MAP REGISTER Address: 0x2A, Reset: 0x00, Name: INT_MAP DATA SYNCHRONIZATION Address: 0x2B, Reset: 0x00, Name: Sync I2C SPEED, INTERRUPT POLARITY, AND RANGE REGISTER Address: 0x2C, Reset: 0x81, Name: Range POWER CONTROL REGISTER Address: 0x2D, Reset: 0x01, Name: POWER_CTL SELF TEST REGISTER Address: 0x2E, Reset: 0x00, Name: SELF_TEST RESET REGISTER Address: 0x2F, Reset: 0x00, Name: Reset RECOMMENDED SOLDERING PROFILE PCB FOOTPRINT PATTERN PACKAGING AND ORDERING INFORMATION OUTLINE DIMENSIONS BRANDING INFORMATION ORDERING GUIDE