BQ294502 Datasheet, PDF (3/18 Pages) Texas Instruments – Overvoltage Protection for 2-Series and 3-Series Cell Li-Ion Batteries

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PIN FUNCTIONS
bq2945xy
1
2
3
4
5
6
Thermal Pad
Pin Name
V3
V2
VSS
V1
VDD
OUT
PWRPAD
bq294502, bq294504, bq294512, bq294515
bq294522, bq294524, bq294532, bq294562
bq294572, bq294582, bq294592
SLUSAJ3C – SEPTEMBER 2011 – REVISED MAY 2012
Type I/O
IA
IA
P
IA
P
OA
—
Description
Sense input for positive voltage of the third cell from the bottom of the stack
Sense input for positive voltage of the second cell from the bottom of the stack
Electrically connected to IC ground and negative terminal of the lowest cell in
the stack
Sense input for positive voltage of the lowest cell in the stack
Power supply
Output drive for external N-Channel FET
VSS pin to be connected to the PWRPAD on the printed circuit board for proper
operation
PIN DETAILS
Description
The voltage sensing for each cell is done independently using a multiplexer. The method of overvoltage detection
is comparing the voltage to an overvoltage protection voltage V_OV. Once the voltage exceeds the programmed
fixed value, the delay timer circuit is activated. This delay (t_DELAY) is fixed for either a 4-s or 6.5-s delay. When
these conditions are satisfied, the OUT terminal is transitioned to a high level. This output (OUT) is released to a
low condition if all of the cell inputs (Vx) are below the OVP threshold minus the Vhys.
VOV
VOV –V HYS
OUT (V)
t DELAY
Figure 1. Timing for Overvoltage Sensing
Sense Positive Input for Vx
This is an input to sense each single battery cell voltage. A series resistor and a capacitor across the cell for
each input is required for noise filtering and stable voltage monitoring.
Output Drive, OUT
The gate of an external N-Channel MOSFET is connected to this terminal. This output transitions to a high level
when an overvoltage condition is detected and after the programmed delay timer. The out will reset to a low level
if the cell voltage falls below the V_OV threshold before the fixed delay timer expires.
Supply Input, VDD
This terminal is the unregulated input power source for the IC. A series resistor is connected to limit the current,
and a capacitor is connected to ground for noise filtering.
Copyright © 2011–2012, Texas Instruments Incorporated
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Product Folder Link(s): bq294502 bq294504 bq294512 bq294515 bq294522 bq294524 bq294532 bq294562
bq294572 bq294582 bq294592