L9945 datasheet(116/144 Pages) STMICROELECTRONICS

116 / 144 page

Figure 29. FSM describing diagnostic priority



Notes:



GADG1003170942PS

SPI READOUT

NON

STB/STG FAIL

Legenda:

Default state

Transition without fault

Transition with fault

via SPI)

also to control

input (applies

channel control

the generic

NON refers to

en_OUT_xx bit

EN refers to the

default state

events lead to

SPI readout

POR, NRES and

turn OFF

to output active

OC failure leads

NON

VOL FAIL

NON

LVT FAIL

NON

VOL FAIL

NON

FAILURE

NON

FAILURE

STG/STB

FAILURE

EN = 0

DIAG

NO OC

NON

VOL FAIL

Note:

In case a diagnostic event occurs during SPI readout, such event is latched and provided with the next

diagnostic request.

6.3

ON state diagnostics

The following diagnostic codes can be set during the output ON state:

•

The diagnostic code corresponding to normal operation while in ON state is "No OC failure" (101);

•

The "No failure" (100) code will be reported only once, after an OFF->ON transition, assuming that "No

OL/STG/STB failure" latch was set while in OFF state and "No OC failure" is detected;

•

The "OC failure" (001) or "OC pin failure" (000) codes will be reported in case of overcurrent detection.

This device protects the external FET against overcurrent (OC) during the ON phase. The device features an

analog comparator with a programmable overcurrent threshold. Sensing is performed measuring the voltage drop

on an external element and comparing it to the programmed threshold. Such threshold can be compensated

against battery and temperature variations for specific applications.

6.3.1

Behavior in case of OC detection

If an OC event is detected, the output is actively shut off and the "OC failure" message is encoded in the

diag_xx[2-0] bit. To prevent FET damage, in case the normal operation gate charge/discharge currents are low (1

mA or 5 mA), the device selects a higher shut off current among the ones available through GCC_config_xx. By

programming the GCC_override_config, it is possible to select the entity of current increase in case of OC, as

shown in the table below. These settings are in common between all channels.

Table 37. Selection of fast shutdown currents in case of OC detection

GCC_override_config

IPU or IPD [mA]

1 → 5

5 → 20

L9945

Safety & diagnostics

DS12275 - Rev 10

page 116/144

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