L9678P datasheet(116/203 Pages) STMICROELECTRONICS

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Deployment drivers

L9678P, L9678P-S

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DocID029274 Rev 3

Figure 25. Deployment loop diagnostics

The leakage diagnostic includes short to battery, short to ground and shorts between loops.

The test is applied to each SFx and SRx pin so shorts can be detected regardless of the

resistance between the squib pins.

6.5.1

Low level diagnostic approach

In this approach, each of the test steps described in the sections below requires user

intervention by issuing the proper SPI command.

High voltage leakage test for oxide isolation check

This test is mandatory to address possible leakages that could not be experienced at low

voltages on SFx or SRx pins. The Isource current generator (ISRC) is enabled on the chosen

SFx pin. To confirm that the SFx pin has then reached a suitable voltage level, a dedicated

ADC measurement on the SFx pin can be requested. Once this test is performed, a leakage

test on SFx and SRx pins can be issued to double check possible leakages.

Leakage to battery/ground diagnostics

Prior to the real test, the Voltage Regulator Current Monitor block (VRCM) has to be tested

and validated. The validation of VRCM goes into verifying both the short to battery and short

to ground flags.

The Isource current generator (ISRC) is first connected to SFx pin to raise its voltage to

VRESDIAG. Then, the Voltage Regulator Current Monitor block (VRCM) is enabled and

connected to the selected SFx pin. The Isink current limited switch (ISNK) is turned off, as

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