Datasheet ADXRS642 (Analog Devices) - 10

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Data Sheet ADXRS642 MODIFYING THE MEASUREMENT RANGE MECHANICAL PERFORMANCE
The ADXRS642 scale factor can be reduced to extend the The ADXRS642 excellent vibration rejection is demonstrated in measurement range to as much as ±450°/sec by adding a single Figure 15 and Figure 16. Figure 15 shows the ADXRS642 output 225 kΩ resistor between the RATEOUT and SUMJ. If an external response with and without 15 g rms 50 Hz to 5 kHz of random resistor is added between RATEOUT and SUMJ, COUT must be vibration. The bandwidth of the gyro was limited to 1600 Hz. proportional y reduced to maintain the correct bandwidth. Performance is similar regardless of the direction of the input
NULL ADJUSTMENT
vibration.
1
The nominal 2.5 V null is for a symmetrical swing range at RATEOUT (1B, 2A). However, a nonsymmetric output swing may be suitable in some applications. Null adjustment is possible
0.1
by injecting a suitable current to SUMJ (1C, 2C). Note that supply disturbances may reflect some null instability. Digital supply noise
0.01
should be avoided, particularly in this case.
/√Hz2 SELF-TEST FUNCTION (°/s) 0.001
The ADXRS642 includes a self-test feature that actuates each of the sensing structures and associated electronics in the same manner, as if subjected to angular rate. It is activated by standard
0.0001
logic high levels applied to Input ST1 (5F, 5G), Input ST2 (4F, 4G), or both. ST1 causes the voltage at RATEOUT to change
0.00001
about −0.3 V, and ST2 causes an opposite change of +0.3 V. The
10 100 1k 10k
014 self-test response fol ows the viscosity temperature dependence
FREQUENCY (Hz)
09770- of the package atmosphere, approximately 0.25%/°C. Activating Figure 15. ADXRS642 Output Response with and Without Random Vibration both ST1 and ST2 simultaneously is not damaging. ST1 and ST2 (15 g rms, 50 Hz to 5 kHz) are fairly closely matched (±2%), but actuating both simultaneously Figure 16 demonstrates the ADXRS642 dc noise response to 5g may result in a small apparent null bias shift proportional to the sine vibration over the 20 Hz to 5 kHz range. As can be seen, degree of self-test mismatch. there are no sensitive frequencies present, and vibration ST1 and ST2 are activated by applying a voltage equal to V rectification is vanishingly smal . As in the previous example, RATIO to the ST1 pin and the ST2 pin. The voltage applied to ST1 and the gyro bandwidth was set to 1600 Hz. ST2 must never be greater than AV
0.12
CC.
CONTINUOUS SELF-TEST 0.10
The on-chip integration of the ADXRS642 gives it higher reliability than is obtainable with any other high volume manufacturing
0.08
method. Also, it is manufactured under a mature BiMOS process
0.06
that has field-proven reliability. As an additional failure detection measure, power-on self-test can be performed. However, some
0.04 (°/s)
applications may warrant continuous self-test while sensing rate. Details outlining continuous self-test techniques are also
0.02
available in the AN-768 Application Note.
0 –0.02 –0.0410 100 1k 10k
015
FREQUENCY (Hz)
09770- Figure 16. ADXRS642 Sine Vibration Noise Response (5 g, 20 Hz to 5 kHz) Rev. A | Page 9 of 12 Document Outline Features Applications General Description Functional Block Diagram Revision History Specifications Absolute Maximum Ratings Rate Sensitive Axis ESD Caution Pin Configuration and Function Descriptions Typical Performance Characteristics Theory of Operation Setting Bandwidth Temperature Output and Calibration Supply Ratiometricity Modifying the Measurement Range Null Adjustment Self-Test Function Continuous Self-Test Mechanical Performance Outline Dimensions Ordering Guide