L9177ATR datasheet(33/55 Pages) STMICROELECTRONICS

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Figure 24. Current limited low side driver diagnosis time diagram

GAPGPS00608

3.5.6

Stepper motor driver OFF diagnosis (EN signal low 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 from switching on. The latched fault is cleared on

request.

3.5.7

Stepper motor driver ON diagnosis (EN signal high 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.

L9177A

Diagnosis

DS12175 - Rev 5

page 33/55

L9177ATR データシート(PDF) 33 Page - STMicroelectronics