AN4650 datasheet(98/102 Pages) STMICROELECTRONICS

98 / 102 page

Self-test

AN4650

98/102

DocID027415 Rev 1

Self-test

The embedded self-test functions allows checking the device functionality without moving it.

10.1

Accelerometer self-test

When the accelerometer self-test is enabled, an actuation force is applied to the sensor,

simulating a definite input acceleration. In this case the sensor outputs exhibit a change in

their DC levels which are related to the selected full scale through the sensitivity value.

The accelerometer self-test function is off when the ST_XL[1:0] bits of the CTRL5_C

sign self-test) or 10b (negative sign self-test).

When the accelerometer self-test is activated, the sensor output level is given by the

algebric sum of the signals produced by the acceleration acting on the sensor and by the

electrostatic test-force. The complete accelerometer self-test procedure is indicated in

Figure 31.

10.2

Gyroscope self-test

The gyroscope self-test allows testing of the mechanical and electrical part of the gyroscope

sensor: when it is activated, an actuation force is applied to the sensor, emulating a definite

Coriolis force, and the seismic mass is moved by means of this electrostatic test-force. In

this case the sensor output exhibits an output change.

The gyroscope self-test function is off when the ST_G[1:0] bits of the CTRL5_C register are

programmed to 00b; it is enabled when the ST_G bits are set to 01b (positive sign self-test)

or 11b (negative sign self-test).

When the gyroscope self-test is active, the sensor output level is given by the algebraic sum

of the signals produced by the velocity acting on the sensor and by the electrostatic test-

force. The complete gyroscope self-test procedure is indicated in Figure 32.

AN4650 Datasheet(PDF) 98 Page - STMicroelectronics