BQ2947_16 Datasheet, PDF (12/24 Pages) Texas Instruments – Overvoltage Protection for 2-Series to 4-Series Cell Li-Ion Batteries

bq2947
SLUSB15E – SEPTEMBER 2012 – REVISED FEBRUARY 2016
9 Application and Implementation
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NOTE
Information in the following applications sections is not part of the TI component
specification, and TI does not warrant its accuracy or completeness. TI’s customers are
responsible for determining suitability of components for their purposes. Customers should
validate and test their design implementation to confirm system functionality.
9.1 Application Information
The bq2947 devices are a family of second-level protectors used for overvoltage protection of the battery pack in
the application. The device, when configuring the OUT pin with active high, drives a NMOS FET that connects
the fuse to ground in the event of a fault condition. This provides a shorted path to use the battery and/or charger
power to blow the fuse and cut the power path. The OUT pin, when configured as active low, can be used to
drive a PMOS FET to connect the fuse to ground instead.
9.2 Typical Applications
9.2.1 Application Configuration for Active High
Figure 12 shows the recommended reference design components.
100 Ω
Pack+
VCELL4
VCELL3
VCELL2
VCELL 1
VDD
1k
V4
1k ^0.1µF
V3
1k ^0.1µF
V2
1k
0 .1 µ F
PWPD
OUT
CD
VSS
V1
0.1 µF 0.1 µF
0 .1 µ F
Pack–
Figure 12. Application Configuration for Active High
9.2.1.1 Design Requirements
NOTE
In the case of an Open Drain Active Low configuration, an external pull-up resistor is
required on the OUT terminal.
Changes to the ranges stated in Table 1 will impact the accuracy of the cell
measurements.
PARAMETER
Voltage monitor filter resistance
Voltage monitor filter capacitance
Supply voltage filter resistance
Supply voltage filter capacitance
CD external delay capacitance
Table 1. Parameters
EXTERNAL COMPONENT
R_IN
C_IN
R_VD
C_VD
C_CD
MIN
900
0.01
100
NOM
1000
0.1
0.1
0.1
MAX
4700
1.0
1000
1.0
1.0
UNIT
Ω
µF
Ω
µF
µF
12
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