TYPICAL APPLICATION CIRCUIT

AC Adapter

VDC

GND

C

IN

1

7

2

5

4

6

8

bq24313

bq24315

bq24080

ChargerIC

SYSTEM

IN

OUT

VBAT

FAULT

CE

C

OUT

C

OUT

R

BAT

R

CE

Host

Controller

R

FAULT

V

PU

R

PU

1

F

m

1

F

m

100kW

47kW

47kW

47kW

R

ILM

DETAILED FUNCTIONAL DESCRIPTION

POWER DOWN

POWER-ON RESET

OPERATION

bq24313

bq24315

Figure 22.

The bq24313 and bq24315 are integrated circuits designed to provide protection to Li-ion batteries from failures

of the charging circuit. The IC continuously monitors the input voltage, the input current and the battery voltage.

For an input overvoltage condition, the IC immediately removes power from the charging circuit by turning off an

internal switch. For an overcurrent condition, it limits the system current at the threshold value, and if the

overcurrent persists, switches the pass element OFF after a blanking period. If the battery voltage rises to an

unsafe level, the IC disconnects power from the charging circuit until the battery voltage returns to an acceptable

value. Additionally, the IC also monitors its own die temperature and switches off if it exceeds 140°C. The input

overcurrent threshold is user-programmable. The IC can be controlled by a processor, and also provides status

information about fault conditions to the host.

The device remains in power down mode when the input voltage at the IN pin is below the undervoltage

threshold UVLO. The FET Q1 connected between IN and OUT pins is off, and the status output, FAULT, is set to

Hi-Z.

The device resets when the input voltage at the IN pin exceeds the UVLO threshold. All internal counters and

to control the inrush current. The soft-start minimizes the ringing at the input (the ringing occurs because the

parasitic inductance of the adapter cable and the input bypass capacitor form a resonant circuit). Because of the

deglitch time at power-on, if the input voltage rises rapidly to beyond the OVP threshold, the device will not

switch on at all, instead it will go into protection mode and indicate a fault on the FAULT pin.

The device continuously monitors the input voltage, the input current, and the battery voltage as described in

detail in the following sections.

Copyright © 2008, Texas Instruments Incorporated

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Product Folder Link(s): bq24313 bq24315