Datasheet ADXL1001, ADXL1002 (Analog Devices) - 10

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ADXL1001/ADXL1002 Data Sheet APPLICATIONS INFORMATION APPLICATION CIRCUIT
The self test feature can be exercised by the user with the For most applications, a single 1 µF capacitor adequately following steps: decouples the accelerometer from noise on the power supply. A 1. Measure the output voltage. band limiting filter at the output provides suppression of out of 2. Turn on self test by setting the ST pin to VDD. band noise and signal. A capacitive load between 100 pF and 3. Measure the output again. 22 nF is recommended. 4. Subtract the two readings and compare the result to the The output amplifier can drive resistive loads up to 2 mA of source expected value from Table 1, while factoring in the current, for example greater than 2.5 kΩ for 5 V operation. If response curve due to supply voltage, if necessary, from the output is to drive a capacitive load greater than or equal to Figure 23. 100 pF, a series resistor of at least 8 kΩ is required to maintain The self test function can be activated at any point during the amplifier stability. normal operation by setting the ST pin to VDD. Self test takes When inactive, the ST and STANDBY pins are forced low. The approximately 300 µs from the assertion of the ST pin to a overrange indicator is an output that can be monitored to result, and acceleration outputs return approximately 300 µs identify the status of the system. after the release of the ST pin. While performing the self test
OPTIONAL
measurement, do not use the accelerometer output to measure
LOW-PASS FILTER
external acceleration.
R V 700 OUT C 600 ) V VSS (m 500 TA L ADXL1002 E ADXL1001 32 31 30 29 28 27 26 25 D T 400 24 1 S E T 23 2 LF 300 E 22 S 3 200 21 ICAL 4 ADXL1001/ P Y ADXL1002 20 T 5 OR 100 19 6 0 18 7 3.3 3.5 3.7 3.9 4.1 4.3 4.5 4.7 4.9 5.1 5.3
022
17 SUPPLY VOLTAGE (V) 8
15431-
9 10 11 12 13 14 15 16
Figure 23. ADXL1002 Typical Self Test Delta vs. Supply Voltage
VDD (3.3V TO 5.25V RATIOMETRIC OUTPUT VOLTAGE 1µF ST (ACTIVE HIGH) SUPPLY VOLTAGE)
021
STANDBY (ACTIVE HIGH)
The ADXL1001/ADXL1002 are tested and specified at V 15431- DD = 5.0 V; however, it can be powered with V Figure 22. ADXL1001/ADXL1002 Application Circuit DD as low as 3.3 V or as high as 5.25 V. Some performance parameters change as the
ON DEMAND SELF TEST
supply voltage is varied. A ful y integrated electromechanical self test function is designed The ADXL1001/ADXL1002 output is ratiometric to the supply into the ADXL1001/ADXL1002. This function electrostatically voltage VDD; therefore, the output sensitivity (or scale factor) actuates the accelerometer proof mass, resulting in a displacement varies proportionally to the supply voltage. At VDD = 5.0 V, the of the capacitive sense fingers. This displacement is equivalent output sensitivity is typical y 40 mV/g and 20 mV/g in the to the displacement that occurs as a result of external acceleration ADXL1002 and ADXL1001, respectively. input. The proof mass displacement is processed by the same signal processing circuitry as a true acceleration output signal, The zero g bias output is ratiometric also and is nominally providing complete coverage of both the electrical and mechanical midscale relative to the supply voltage (VDD/2). responses of the sensor system. Rev. 0 | Page 10 of 14 Document Outline FEATURES APPLICATIONS FUNCTIONAL BLOCK DIAGRAM GENERAL DESCRIPTION TABLE OF CONTENTS REVISION HISTORY SPECIFICATIONS ABSOLUTE MAXIMUM RATINGS THERMAL RESISTANCE RECOMMENDED SOLDERING PROFILE ESD CAUTION PIN CONFIGURATION AND FUNCTION DESCRIPTIONS TYPICAL PERFORMANCE CHARACTERISTICS THEORY OF OPERATION MECHANICAL DEVICE OPERATION OPERATING MODES Measurement Mode Standby BANDWIDTH APPLICATIONS INFORMATION APPLICATION CIRCUIT ON DEMAND SELF TEST RATIOMETRIC OUTPUT VOLTAGE INTERFACING ANALOG OUTPUT BELOW 10 kHz INTERFACING ANALOG OUTPUT BEYOND 10 kHz OVERRANGE MECHANICAL CONSIDERATIONS FOR MOUNTING LAYOUT AND DESIGN RECOMMENDATIONS OUTLINE DIMENSIONS ORDERING GUIDE