L9965P datasheet(63/104 Pages) STMICROELECTRONICS

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3.13

Ground loss monitor (GNDMON)

To detect failures in grounding, the IC integrates a ground loss monitor that is always enabled when it is in DIAG,

NORMAL and ARM states.

3.13.1

Ground loss monitor diagnostics

Table 38. Ground loss monitor diagnostics

Fault

type

Assertion condition

IC reaction to

assertion

Release condition

reaction

to flag

clear

Maskable

PGND

LOSS

If a differential voltage

greater than

VPGND_LOSS_TH arises

between GND and

PGND for a time longer

than tPGND_LOSS_FLT,

the PGND loss fault is

acknowledged

The PGND_LOSS flag

is set

FAULTN line is

asserted

The “fire inhibit” signal

is set

If the differential voltage

between GND and

PGND falls below

VPGND_LOSS_TH for a

time longer than

tPGND_LOSS_FLT, the fault

flag can be cleared by

MCU

Pyro-fuse

fire is

possible

again

Non-maskable

BSTGND

LOSS

If a differential voltage

greater than

VBSTGND_LOSS_TH

arises between GND

and BSTGND for a time

longer than

tBSTGND_LOSS_FLT, the

BSTGND loss fault is

acknowledged

The BSTGND_LOSS

flag is set

FAULTN line is

asserted

If enabled, ERBST is

disabled

If disabled, ERBST is

not turned-on

(diagnostic is active

thanks to IBSTGND_PU

internal pull-up)

The “fire inhibit” signal

is set

If the differential voltage

between GND and

BSTGND falls below

VBSTGND_LOSS_TH for a

time longer than

tBSTGND_LOSS_FLT, the

ERBST is automatically

reenabled and the fault

flag can be cleared by

MCU

Pyro-fuse

fire is

possible

again

BSTGND_LOSS_MSK

masks the inhibition of

pyro-fuse fire

commands

3.13.2

Ground Loss monitor electrical parameters

All parameters are tested and guaranteed in the following conditions, unless otherwise noted: all supplies

according to the Table 3; TJ according to the Table 2.

Table 39. Ground Loss monitor electrical parameters

Symbol

Parameter

Test condition Min Typ Max Unit

VPGND_LOSS_TH

PGND ground loss detection threshold

300

920

GND1, GND2, PGND

tPGND_LOSS_FLT

PGND ground loss detection filter time Tested by SCAN 46

µs

GND1, GND2, PGND

VBSTGND_LOSS_TH

BSTGND ground loss detection

threshold

300

920

GND1, GND2,

BSTGND

tBSTGND_LOSS_FLT

BSTGND ground loss detection filter

time

Tested by SCAN 1.9 2.3

2.7

µs

GND1, GND2,

BSTGND

IBSTGND_PU

BSTGND pull-up current

µA

BSTGND

L9965P

Functional description

DS14702 - Rev 4

page 63/104

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