BQ24314EVM Datasheet, PDF (10/26 Pages) Texas Instruments – OVERVOLTAGE AND OVERCURRENT PROTECTION IC

bq24314
bq24316
SLUS763C – JULY 2007 – REVISED OCTOBER 2007
www.ti.com
TYPICAL APPLICATION CIRCUIT
V_OVP = 6.8V, I_OCP = 1000mA, BV_OVP = 4.35V (Terminal numbers shown are for the 2×2 DSG package)
AC Adapter
VDC
GND
1 ^IN
C_IN
1 mF
OUT ₈
1 mF
bq24316DSG
C_OUT
bq24080
Charger IC
VBAT ₆
R_BAT
100 kW
SYSTEM
V_PU
7
R_ILM
25 kW
FAULT ₄
CE ₅
2
R_PU 47 kW
47 kW
R_FAULT
47 kW
R_CE
Host
Controller
Figure 23.
DETAILED FUNCTIONAL DESCRIPTION
The bq24314 and bq24316 are highly 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. 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
becomes too hot. 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 V_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 t_DGL(PGOOD) for the input voltage to stabilize. If, after
t_DGL(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.
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