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| BQ24314A Datasheet, PDF (10/21 Pages) Texas Instruments – OVERVOLTAGE AND OVERCURRENT PROTECTION IC AND Li+ CHARGER FRONT-END PROTECTION IC | |||
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bq24314A
SLUS811 â MARCH 2008
www.ti.com
TYPICAL APPLICATION CIRCUIT
VOVP = 6.8V, IOCP = 1000mA, BVOVP = 4.35V (Terminal numbers shown are for the 2Ã2 DSG package)
AC Adapter
VDC
GND
1 IN
CIN
1 mF
OUT 8
1 mF
bq24314A
COUT
bq24080
Charger IC
VBAT 6
RBAT
100 kW
SYSTEM
VPU
7
RILM
24.9 kW
FAULT 4
CE 5
2
RPU
47 kW
47 kW
RFAULT
47 kW
RCE
Host
Controller
Figure 20.
DETAILED FUNCTIONAL DESCRIPTION
The bq24314A is a highly integrated circuit 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. In case
of an input overvoltage condition, the IC immediately removes power from the charging circuit by turning off an
internal switch. In the case of 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.
POWER DOWN
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.
POWER-ON RESET
The device resets when the input voltage at the IN pin exceeds the UVLO threshold. All internal counters and
other circuit blocks are reset. The IC then waits for duration tDGL(PGOOD) for the input voltage to stabilize. If, after
tDGL(PGOOD), the input voltage and battery voltage are safe, FET Q1 is turned ON. The IC has a soft-start feature
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). Figure 2 shows
the power-up behavior of the device. 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, as shown in Figure 3.
10
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Copyright © 2008, Texas Instruments Incorporated
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