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BQ77216 Circuit Module Use
3 BQ77216 Circuit Module Use
The BQ77216 circuit module contains the BQ77216 IC and related circuitry to demonstrate the features of the
IC. The board does not control current, the COUT and DOUT signals pass through 100 ohm resistors and are
available on the J4 connector. COUT and DOUT are also used to control the gate of N-channel FETs, the open
drain outputs are also available on J4. A thermistor provides temperature sensing on the board. Other
components provide support for the IC and connections to the board. Basic operation is described in the
BQ77216 EVM Getting Started Guide
Physical Construction
section.
3.1 Cell Simulator
The EVM includes a resistive cell simulator made up of 499-Ω series resistors. The taps of the resistor network
are connected to the cell inputs using shunts on the J5 and J6 headers. BAT- is always connected to the resistor
divider network. Install a shunt on the top cell location to connect the BAT+ to the resistor divider to provide
simulated voltages for the other cell inputs. With the top shunt installed the resistor divider is connected and
shunts on the lower cell positions will connect the inputs to the simulated voltages. With the top shunt removed
all lower inputs with installed shunts are pulled to VSS. There is no indication of the cell simulator connection,
the user must be aware of the shunt installation. The 499-Ω resistors provide a load of 2 mA per volt on each
cell.
3.2 Reducing the Cell Count
The BQ77216 cell count is reduced by shorting unused cells, normally from the top down but cells between the
top and bottom may be shorted. The inputs are usually shorted at the IC as shown in the data sheet. The bottom
cell must be used for proper operation. Power for the IC comes from the BAT+ terminal so it must be connected
when using the EVM. While not recommended the inputs of the EVM can typically be shorted at the terminal
block for quick evaluation. For the best transient environment and to match the data sheet example, 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 also suggested since it should be apparent if the board is re-used for a
different cell count. While different connections are possible,
14 cells.
Unused Cell
(Numbered from Bottom
Cell 1)
Cell 16
Cell 15
3.3 Connecting Cells
The EVM is constructed with a single connection to the top and bottom of the cell stack. Cell voltage for these
cells is sensed on the board. The board is not configured to control current into or out of the cells.
The cell simulator provides resistors between the cell inputs. When the cell simulator shunts are installed, these
resistors will load the cells and divide the voltage to any unconnected inputs as cells are connected. The shunts
must be removed or the cells will be discharged by the constant drain of the cell simulator resistors.
BAT- is the reference voltage for the IC and should be connected first. After BAT- cells may be connected in any
order. Cell connection from the bottom up minimizes the voltage step size applied to the board. Recommended
connection sequence for the EVM when connecting cells is bottom up:
1. Connect BAT–
2. Connect cells bottom up; CELL1, CELL2, CELL3 ...
3. Be sure the cell simulator shunts are removed
6
BQ77216 Evaluation Module
section. For details of the circuit, refer to the
Table 3-1. Reducing Cell Count
Short Cell Input
Input Resistor to
Terminals
Remove
BAT+ to CELL15
CELL15 to CELL14
Copyright © 2020 Texas Instruments Incorporated
Table 3-1
shows configuration recommendations for
Replace Capacitor
with 0 ohm
R2
C2
R3
C3
SLUUC95A – AUGUST 2020 – REVISED NOVEMBER 2020
www.ti.com
BQ77216EVM Circuit Module
IC Inputs Shorted
VC16 to VC15
VC15 to VC14
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