L9679P datasheet(189/279 Pages) STMICROELECTRONICS

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DS11627 Rev 7

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L9679P

DC sensor interface

278

Each output is protected against



Overload conditions by current limit



Ground offset between the ECU and the loads of up to ±1 V.



Loss of ECU battery



Loss of ground



Unpowered shorts to battery



Shorts to ground

11.1

Passenger inhibit interface

L9679P provides a feature to deactivate passenger restraint devices based on a

preprogrammed mask. It generates a signal (PSINHINT) based on microcontroller-initiated

measurements performed on DC Sensor channel 0. The PSINHINT signal is bitwise AND-

ed with the LOOP_MATRIX_PSINH mask register, allowing selective deactivation of

squib/pyroswitch loops independent of microcontroller control. This signal is also inverted

and output on the PSINHB pin of the IC to activate externally controlled squib/pyroswitch

loops.

Figure 48. Passenger inhibit logic diagram

An upper and lower threshold is preprogrammed via SPI by writing the desired 10-bit values

into the PADTHRESH_HI and PADTHRESH_LO registers during the Diag state. These

thresholds define the measurement window where the passenger restraints are active. Any

measurement outside this window will result in the assertion of the PSINHINT signal (as

described below), thereby deactivating the squib/pyroswitch loops identified in the PSINH

mask. The PSINH mask is also preprogrammed during the Diag state.

ADCREQ_y[6:0] = DCSx_I

SYS_CFG(DCS_PAD_V)

ADCREQ_y[6:0] = DCSx_V

SAFING state

DCS0 ON

NEWDATA_y

In window

DEP_DISABLED state

DIAG state

DSTEST(PSINH)

SET

to 1s

Down CTR

SSM RESET

CLR

PSINHB

PSINHINT

PSINHSEL

PSINH_POL

0: Outside window inh

1: Inside window inh

SWCTRL(CHID) = ‘0000’

ADCRES_y[9:0]

PADTHRESH_HI

PADTHRESH_LO

250Hz

GAPGPS02289

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