L9177 datasheet(36/49 Pages) STMICROELECTRONICS

36 / 49 page

Functional description

L9177

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DocID17617 Rev 1

Figure 24. Lamp driver diagnosis time diagram

4.5.6

Stepper motor driver off diagnosis (EN signal high and output in high

impedance state)

In OFF condition Short to GND/Short to Vb or Open Load condition is continuously detected

through a deglitch filter of 125 μs ±25 %, after Tmask masking time of 1 ms ±25 % to filter

ON/ OFF transition. To avoid false diagnostic due to motor residual movement, the stepper

has to be disabled at least 40 ms after the PWL signal has been disabled. A fault longer

than deglitch time is latched. Off state diagnostic fault can be overwritten by on state fault.

Off state fault does not prevent the stepper to switch on. The latched fault is cleared on

request.

4.5.7

Stepper motor driver on diagnosis (EN signal Low and output driven by

input commands)

In ON condition when over current fault is detected and validated after digital filtering time

Tdgc of 20 μs ±25 %, the bridge is turned OFF and the fault is latched. The bridge is turned

ON again by input command EN transition. The latched fault is cleared on request. Over

current fault has higher priority with respect to OFF condition faults. Each Bridge has

dedicated fault diagnosis detection coded by three bits.

L9177 Datasheet(PDF) 36 Page - STMicroelectronics