BQ294602_17 Datasheet, PDF (7/21 Pages) Texas Instruments – Single-Cell Protector for Li-Ion Batteries

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8 Detailed Description
bq294602, bq294604, bq294682, bq294624
SLUSAS0D – DECEMBER 2011 – REVISED APRIL 2017
8.1 Overview
The bq2946xx is a second-level overvoltage (OV) protector for a single cell. The cell voltage is compared to a
protection voltage threshold, V_OV. The protection threshold is preprogrammed at the factory with a range from
3.85 V to 4.65 V. When the OVP is triggered, the OUT pin goes high to activate an external N-channel FET,
which conducts a low-impedance path to blow a fuse.
8.2 Functional Block Diagram
R _VD
C_VD
VDD
PACK +
R_IN
V1
C_IN
VSS
V_OV
OSC
REG
INT_ EN
Delay
Timer
OUT
PWRPAD
PACK –
8.3 Feature Description
The method of overvoltage detection is comparing the cell voltage to an OVP threshold voltage V_OV. Once the
cell voltage exceeds the programmed fixed value V_OV, the delay timer circuit is activated. This delay (t_DELAY) is
fixed for 4 seconds for the bq294602 device. When these conditions are satisfied, the OUT terminal is
transitioned to a high level. This output (OUT) is released to a low condition if the cell input (V1) is below the
OVP threshold minus the V_HYS.
VOV
VOV – VHYS
OUT (V)
t DELAY
Figure 5. Timing for Overvoltage Sensing
8.3.1 Sense Positive Input for V1
This is an input to sense single battery cell voltage. A series resistor and a capacitor across the cell is required
for noise filtering and stable voltage monitoring.
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