ADXRS642 Analog Devices, ADXRS642 Datasheet - Page 8

• Manufacturer Part Number: ADXRS642
• Description: Vibration Rejecting Yaw Rate Gyro
• Manufacturer: Analog Devices

www.DataSheet4U.com
ADXRS642
NULL ADJUSTMENT
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
by injecting a suitable current to SUMJ (1C, 2C). Note that supply
disturbances may reflect some null instability. Digital supply noise
should be avoided, particularly in this case.
SELF-TEST FUNCTION
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
logic high levels applied to Input ST1 (5F, 5G), Input ST2
(4F, 4G), or both. ST1 causes the voltage at RATEOUT to change
about −0.3 V, and ST2 causes an opposite change of +0.3 V. The
self-test response follows the viscosity temperature dependence
of the package atmosphere, approximately 0.25%/°C.
Activating both ST1 and ST2 simultaneously is not damaging.
ST1 and ST2 are fairly closely matched (±2%), but actuating
both simultaneously may result in a small apparent null bias
shift proportional to the degree of self-test mismatch.
ST1 and ST2 are activated by applying a voltage equal to V
to the ST1 pin and the ST2 pin. The voltage applied to ST1 and
ST2 must never be greater than AV
CONTINUOUS SELF-TEST
The on-chip integration of the ADXRS642 gives it higher reliability
than is obtainable with any other high volume manufacturing
method. Also, it is manufactured under a mature BiMOS process
that has field-proven reliability. As an additional failure detection
measure, power-on self-test can be performed. However, some
applications may warrant continuous self-test while sensing rate.
Details outlining continuous self-test techniques are also
available in the
MECHANICAL PERFORMANCE
The ADXRS642 excellent vibration rejection is demonstrated in
the graphs below. Figure 6 shows the ADXRS642 output
AN-768
Application Note.
CC
.
RATIO
Rev. Pr. A | Page 8 of 10
response with and without 15g RMS 50Hz to 5kHz of random
vibration. Bandwidth of the gyro was limited to 1600Hz.
Performance is similar regardless of the direction of input
vibration.
Figure 7 demonstrates the ADXRS642 DC bias response to 5g
Sine vibration over the 20Hz to 5kHz range. As can be seen,
there are no sensitive frequencies present and vibration
rectification is vanishingly small. As in the previous example
gyro bandwidth was set to 1600Hz.
Figure 6. ADXRS642 Output Response With and Without Random Vibration
Figure 7. ADXRS642 Sine Vibration Output Response (5g, 20Hz to 5kHz)
‐0.02
‐0.04
0.00001
0.12
0.08
0.06
0.04
0.02
0.0001
0.1
0.001
0.01
0
0.1
10
1
10
Preliminary Technical Data
(15g RMS, 50Hz to 5kHz)
100
100
Frequency
Hz
1000
1000
10000
10000