ADXRS622

Rev. C | Page 10 of 12

ADXRS622 AND SUPPLY RATIOMETRICITY

The ADXRS622 RATEOUT and TEMP signals are ratiometric

ADXRS622 is most easily used with a supply-ratiometric analog-

to-digital converter (ADC) that results in self-cancellation of errors

due to minor supply variations.

There is some small error due to nonratiometric behavior. Typical

ratiometricity error for null, sensitivity, self-test, and temperature

output is outlined in Table 4.

Table 4. Ratiometricity Error for Various Parameters

Parameter

V

V

ST1

Mean

0.3%

0.09%

Sigma

0.21%

0.19%

ST2

Mean

−0.15%

−0.2%

Sigma

0.22%

0.2%

Null

Mean

−0.3%

−0.05%

Sigma

0.2%

0.08%

Sensitivity

Mean

0.003%

−0.25%

Sigma

0.06%

0.06%

V

TEMP

Mean

−0.2%

−0.04%

Sigma

0.05%

0.06%

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 ADXRS622 includes a self-test feature that actuates each of

the sensing structures and associated electronics 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 −

0.5 V, and ST2 causes

an opposite change of +0.5 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 (±5%), but actuating

both simultaneously may result in a small apparent null bias

shift proportional to the degree of self-test mismatch.

to the ST1 pin and the ST2 pin. The voltage applied to ST1 and

CONTINUOUS SELF-TEST

The on-chip integration of the ADXRS622 gives it higher reliability

than is obtainable with any other high volume manufacturing

method. In addition, 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 AN-768 Application Note.