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2.3.5 Reducing the Cell Count
The BQ76905 must have the top and bottom cells used for proper operation. Cell count can be reduced by
shorting the unused cell inputs from the next-to-top down. Cell count can be reduced for basic evaluation by
shorting unused cells at the input terminal block. Follow the recommendations in the data sheet for which cells to
short. This works for both operation with the cell simulator and cells, but can have some side effects in transient
tests because the shorted resistors are parallel to the cell IC where the capacitor provides a signal path to
the used input. See
Figure 2-4
evaluation with reduced cells in a transient environment, short the VCx pins at the capacitor and remove the
unused input resistor. When using the cell simulator, shorting the unused cell at the terminal block is still required
to eliminate the simulated cell voltage. Shorting the cell inputs at the terminal block screw terminals is suggested
since the cell inputs are apparent if the board is re-used for a different cell count.
recommendations for reduced cell count, this table assumes the board has been set-up as detailed in
By default, the BQ76905 EVM has VC4A/B and VC3A/B shorted at the IC inputs. However, the user
must make sure to also short CELL6 to CELL5 and CELL4 to CELL3 on the cell input terminals prior
to making any cell reduction, as explained in
Unused cell
(numbered from bottom
cell 1)
Cell 4
Cell 3
DC Power Supply
+ -
Figure 2-4. Example 3 Cell Simple Evaluation Configuration
SLUUCY9 – NOVEMBER 2023
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for an example of simple reduced cell configuration for 3 cells. For the best
Section
Table 2-1. Reducing Cell Count
Short cell input
Input resistor to
terminals
remove
CELL5 to CELL4
CELL3 to CELL2
R11
Short
CELL6 all the way
down to CELL2
Install cell
simulator shunts
Copyright © 2023 Texas Instruments Incorporated
3.
Replace capacitor with
0 ohm
R8
C7
C9
Hardware
Table 2-1
shows configuration
Section
IC inputs shorted
VC4A/B to VC3A/B
VC3A/B to VC2
BQ76905 Evaluation Module
3.
7
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