L9961 datasheet(39/65 Pages) STMICROELECTRONICS

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3.8.3

MCU emergency reset (FAULTN_SAFE)

MCU should normally manage the communication with battery charger, ensuring cells are properly charged

to 100% state of charge. In case MCU operation fails, the battery cells could be overcharged, leading to fire/

explosion hazard.

L9961 can reset the MCU should a cell overvoltage condition be detected. This is done connecting the

FAULTN_SAFE open-drain output to the MCU reset pin (active low).

When overvoltage failures are directed to FAULTN_SAFE pin, the output is pulled low for TFAULTN_SAFE_LOW to

allow proper reset of the MCU.

3.8.3.1

Electrical parameters

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

VB according to the operating range of Table 2; TJ according to the operating range of Table 5.

Table 29. Digital output electrical characteristics

Symbol

Parameter

Test conditions

Min.

Typ.

Max.

Unit

TFAULTN_SAFE_LOW

FAULTN_SAFE low interval

Tested by SCAN

104

120

μs

FAULTN_SAFE

3.8.4

Electrical parameters

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

VB according to the operating range of Table 2; TJ according to the operating range of Table 5.

Table 30. Digital output electrical characteristics

Symbol

Parameter

Test conditions

Min.

Typ. Max. Unit

VIN_L

Low input level

Valid for FAULTN, SDA, SCL

Slow rising ramp on

input pin

0.8

1.8

SCL, FAULTN

VIN_HYS

Input hysteresis

Valid for FAULTN, SDA, SCL

Input considered high

when VIN > VIN_L +

VIN_HYS

0.1

0.5

SCL, FAULTN

VOUT_L

Low output level

IOUT = 2 mA

0.4

RDY

VOUT_H

High output level

IOUT = 2 mA

VREG-0.4

VREG

RDY

TOUT_RISE

Output rise time

Valid for RDY

Cload=120 pF

From 20 to 80% of final

value

RDY

TOUT_FALL

Output fall time

Valid for RDY.

Cload=120 pF

From 80 to 20% of initial

value

RDY

VOPEN_DRAIN

Open-drain equivalent ON

resistance measurement

Valid for SDA, FAULTN,

FAULTN_SAFE, OD

IOD=2 mA

0.02

0.15

SDA,

FAULTN, OD,

FAULTN_SAFE

3.9

I2C communication interface

L9961 uses an I2C slave peripheral interface to communicate with a host MCU on an addressed I2C bus.

The I2C peripheral uses two lines to implement communication:

•

SCL (Serial CLock): a digital input receiving clock from the master unit of the I2C bus.

•

SDA (Serial DAta): a digital input/output used for sending and receiving data clocked by the master unit of

the I2C bus

L9961

I2C communication interface

DS14012 - Rev 3

page 39/65

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