L9659 datasheet(27/51 Pages) STMICROELECTRONICS

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L9659

Functional description

Doc ID 022048 Rev 2

27/51

3.4.4

Squib diagnostics

Overview

The ASIC is able to perform the following diagnostics

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Short to battery and ground on both SQHx and SQLx pins with or without a squib

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Loop to loop diagnostics

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Squib resistance measurement

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Squib High resistance

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High side safing FET diagnostics

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VRESx voltage status

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High and low side FET diagnostics

Below is a block diagram showing the components involved in the squib diagnostics.

Figure 9.

Squib diagnostics block diagram

Short to battery/ground and loop to loop diagnostics

The leakage diagnostic includes a short to battery, a short to ground and a short between

loop tests. The test will be run for each SQHx and SQLx pin so that shorts can be detected

regardless of the resistance between the squib pins.

Normal short to battery/ground diagnostics.

For the test the internal VRCM is switched on and connected to the selected pin (SQHx or

SQLx) pin. The IPD bit will be selected to be OFF which will deactivate the pulldown current

L9659 Datasheet(PDF) 27 Page - STMicroelectronics