L9177ATR datasheet(30/55 Pages) STMICROELECTRONICS

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3.5.2

Overvoltage shut down

If the VB_off voltage is reached after Tdgc filtering time of 30 µs ±25 % the device enters a safety state where

the main outputs are switched-off. Voltage regulators, all low side channels, stepper motor driver and KLINE are

switched off and reset is asserted. As soon as the battery goes below VB_off minus VB_off_h the device recovers

standard operation.

3.5.3

Undervoltage shut down

If the VB_UV voltage is reached after analog Tdgc 1 µs ±20 % filtering time the device enters a safety state where

main outputs are switched-off. Voltage regulators, all low side channels, stepper motor driver and KLINE are

switched off. As soon as the battery rises above VB_UV plus the hysteresis the device recovers normal operation.

Figure 21. An example of under and over voltage time diagram

LIMITED VB

KEY

VDD

Vth_UV Tht

Td_UV_rst

TfUV_reset

Tdgc_VB_OV

Td_UV_rst

VDD_TRK

HS_OUT

RST

BATTERY LINE

CONNECTION

STAND-BY IGNITION KEY

SWITCH ON

IGNITION KEY

SWITCH OFF

STAND-BY

VDD

UNDERVOLTAGE

VB OVERVOLTAGE

PROTECTION

Td_UV_rst

Vth_UV Tht

VB_off

GADG0412171117PS

3.5.4

Low side on/off diagnosis (INJ, RLY's, TACH, O2H)

About low side channels OFF diagnosis, the device issues a masking filter Tmask after channel turning off (falling

edge of driving command) to avoid false fault detecting due to output transition from low to high. Tmask is of 1 ms

±25 % for all channels except for the relays, for which Tmask is 3.5 ms ±25 %. Once masking time has expired

a deglitch filter Tdgc_noise of 3.6 µs ±40 % for noise immunity is activated. 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

driver from switching on. The latched fault is cleared on request.

During on-phase if an over current fault occurs the drivers enter in current limitation condition for a digital filtering

time Tdgc of 20 µs ±25 %,then it is switched OFF and the fault is latched. The channel is turned ON again by

input command transition. The latched fault is cleared on request via SPI.

Over current fault has higher priority respect to OFF condition faults.

L9177A

Diagnosis

DS12175 - Rev 5

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