L9961 datasheet(29/63 Pages) STMICROELECTRONICS

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3.5.3

Overcurrent monitor

When the CSA is enabled, L9961 can protect the battery pack from overcurrent events in both charge and

discharge directions. The absolute value of each current sample is compared to a programmable digital threshold

CSA.

This diagnostic can be enabled via OVC_EN bit and covers the failures listed in Table 20.

To avoid false detections, overcurrent thresholds shall only be modified while OVC_EN = 0.

The recommended re-engagement strategy in case of persistent OVC failure detection is:

•

Poll the PERSIST_OVC_<x> flags for at least 5TCUR_FILTER to check if fault is still present

–

If the flag can be cleared, fault has disappeared and FET can be re-engaged

–

Otherwise, re-engaging the FET is not recommended and SW should let L9961 blow the FUSE (if not

masked)

Table 20. Overcurrent diagnostics

Fault type

Assertion condition

IC reaction to

assertion

Release condition

IC reaction to flag

clear

Maskable

Overcurrent in charge

If the ISENSEM

– ISENSEP voltage

raises above

VOVC_CHG_TH, the

OVC_CHG fault is

acknowledged.

The OVC_CHG flag is

set

If the ISENSEM

– ISENSEP voltage

falls below VOVC_TH,

the OVC_CHG flag

can be cleared by

MCU

The Charge FET

is restored to the

status defined by the

CHG_ON bit

CSA_EN masks

measurement

execution. When

disabled, the

OVC_CHG flag can

always be cleared

The charge FET is

turned OFF

FAULTN line is

released

OVC_EN masks

diagnostic execution

and all reactions.

When disabled, the

OVC_CHG flag can

always be cleared

FAULTN line is

asserted

OVC_CHG_PRDRV_

MSK masks reaction

on CHG pin

OVC_CHG_FAULTN_

MSK masks reaction

on FAULTN pin

Persistent charge

current

If the CHG FET

is OFF (either

commanded by

user or forced

by diagnostics) and

the ISENSEM –

ISENSEP voltage

raises above

VPERSIST_OVC_TH,

for 4 consecutive

samples, the

PERSIST_OVC_CHG

fault is acknowledged.

The

PERSIST_OVC_CHG

flag is set

If the ISENSEM

– ISENSEP

voltage falls below

VPERSIST_OVC_TH for

4 consecutive

samples, the

PERSIST_OVC_CHG

flag can be cleared by

MCU

FUSE pre-driver is

disabled

CSA_EN masks

measurement

execution. When

disabled, the

PERSIST_OVC_CHG

flag can always be

cleared

FUSE pre-driver is

enabled

If CHG FET is

ON and OVC_EN

is ENABLE, the

PERSIST_OVC_CHG

counter is reset to 0

FAULTN line is

released

OVC_EN masks

diagnostic execution

and all reactions.

When disabled, the

PERSIST_OVC_CHG

flag can always be

cleared

FAULTN line is

asserted

PERSIST_OVC_CHG

_FUSE_MSK masks

reaction on FUSE pin

PERSIST_OVC_CHG

_FAULTN_MSK

masks reaction on

FAULTN pin

L9961

Current conversion routine

DS14012 - Rev 1

page 29/63

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