L9965P datasheet(44/104 Pages) STMICROELECTRONICS

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3.7.2.4

Pyro outputs leakage test

This step aims at verifying that PF/PR pins are floating, with no parasitic leakage towards battery or ground.

This test requires the VRCM check to verify that VRCM output and diagnostic thresholds are in range. To achieve

safety targets, it is strongly recommended to apply such a strategy before running this test.

Figure 21. Pyro outputs leakage test

RPYRO

CESD

VVRCM_REF

o_pf_pr_sel

The diagnostic works as follows:

•

PF leakage test:

–

The VRCM is connected to PF and starts charging the PF node to VVRCM_REF.

–

If no leakage is present, the voltage on PF pin is VVRCM_REF and no current is sunk or sourced by the

VRCM.

–

If there is a leakage to battery, the VRCM sinks current trying to force VVRCM_REF. If the sunk current

is greater than ILEAK_SINK_TH for tVRCM_LEAK_FLT, the PF_STB flag is set.

–

If there is a leakage to the ground, the VRCM sources current trying to force VVRCM_REF. If the

sourced current is greater than ILEAK_SOURCE_TH for tVRCM_LEAK_FLT, the PF_STG flag is set.

•

PR leakage test:

–

The VRCM is connected to the PR and starts charging the PR node to VVRCM_REF.

–

If no leakage is present, the voltage on PR pin is VVRCM_REF and no current is sunk or sourced by

the VRCM.

–

If there is a leakage to battery, the VRCM sinks current trying to force VVRCM_REF. If the sunk current

is greater than ILEAK_SINK_TH for tVRCM_LEAK_FLT, the PR_STB flag is set.

–

If there is a leakage to ground, the VRCM sources current trying to force VVRCM_REF. If the sourced

current is greater than ILEAK_SOURCE_TH for tVRCM_LEAK_FLT, the PR_STG flag is set.

The leakage test diagnostic step duration is tLEAK_TEST.

L9965P

Functional description

DS14702 - Rev 4

page 44/104

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