L9961 datasheet(19/63 Pages) STMICROELECTRONICS

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3.4.2

Battery stack monitor (VB)

The battery stack monitor, (VB), of the voltage conversion routine monitors the battery stack voltage measuring

the VB pin through an internal divider.

This function is enabled by programming the corresponding VB_EN I2C bit: if disabled, this step is skipped.

To limit power consumption, the internal voltage divider is connected to VB pin at the beginning of the

Section 3.4 Voltage conversion routine and it is disconnected right after the VB measurement step is completed.

Stack voltage measurements are stored in the VB_MEAS register and compared to programmable thresholds in

order to detect the failures listed in Table 12.

Table 12. Battery stack monitor diagnostics

Fault type

Assertion condition

IC reaction to

assertion

Release condition

IC reaction to flag

clear

Maskable

VB UV

If VB voltage falls

below VB_UV_TH,

the corresponding

UV counter is

incremented by 1

The VB_UV flag is set

If VB voltage raises

above VB_UV_TH,

the corresponding

UV counter is

decremented by 1.

The discharge FET

is restored to the

status defined by the

DCHG_ON bit

VB_EN masks

measurement

execution. When

disabled, the VB_UV

flag can always be

cleared upon read

If the UV

counter reaches

VB_UV_CNT_TH, it

saturates and the

VB UV fault is

acknowledged

The discharge FET is

turned OFF

If the UV counter

reaches zero, the

VB_UV flag can be

cleared by MCU

FAULTN line is

released

VB_UV_PRDRV_MS

K masks reaction on

DCHG pin

FAULTN line is

asserted

VB_UV_FAULTN_MS

K masks reaction on

FAULTN pin

VB OV

If VB voltage raises

above VB_OV_TH,

the corresponding

OV counter is

incremented by 1

The VB_OV flag is set

If VB voltage falls

below VB_OV_TH,

the corresponding

OV counter is

decremented by 1.

The charge FET

is restored to the

status defined by the

corresponding I2C bit

VB_EN masks

measurement

execution. When

disabled, the VB_OV

flag can always be

cleared upon read

If the OV

counter reaches

VB_OV_CNT_TH, it

saturates and the

VB OV fault is

acknowledged

The charge FET is

turned OFF

If the OV counter

reaches zero, the

VB OV flag can be

cleared by MCU

FAULTN line is

released

VB_OV_PRDRV_MS

K masks reaction on

CHG pin

FAULTN_SAFE is

pulled low for

TFAULTN_SAFE_LOW

VB_OV_RST_MSK

masks reaction

FAULTN_SAFE pin

FAULTN line is

asserted

VB_OV_FAULTN_MS

K masks reaction on

FAULTN pin

VB vs. sum of cells

plausibility fail

If the absolute value

of the difference

between VB_MEAS

and VCELL_SUM is

greater than

VB_VSUM_MAX_DIF

F_TH, the plausibility

check fail is

acknowledged

The

VB_SUM_CHECK_F

AIL flag is set

If the absolute value

of the difference

between VB_MEAS

and VCELL_SUM

falls below the

VB_VSUM_MAX_DIF

F_TH, the

VB_SUM_CHECK_F

AIL flag can be

cleared by MCU

The charge FET

is restored to the

status defined by the

CHG_ON bit

VB_EN masks

measurement

execution. When

disabled, the

VB_SUM_CHECK_F

AIL flag can always

be cleared upon read

Both charge and

Discharge FETs are

turned OFF

The discharge FET

is restored to the

status defined by the

DCHG_ON bit

VB_SUM_CHEC_PR

DRV_MSK masks

reaction on CHG/

DCHG pins

Balancing is

interrupted on all cells

FUSE pre-driver is

disabled

VB_SUM_CHEC_FU

SE_MSK masks

reaction on FUSE pin

FUSE pre-driver is

enabled

Balancing FETs are

restored to the

status defined by

the corresponding

BAL<x>_ON bit

VB_SUM_CHEC_BA

L_MSK masks

reaction on balancing

L9961

Voltage conversion routine

DS14012 - Rev 1

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