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the measurement loop speed when cell balancing is active. The BQ769142 device will insert current-only
measurements after each voltage and a temperature scan loop to slow down voltage measurements and
thereby increase the average balancing current.
The device includes an internal die temperature check, to disable balancing if the die temperature exceeds a
programmable threshold. However, the customer should still carefully analyze the thermal effect of the balancing
on the device in system. Based on the planned ambient temperature of the device during operation and the
thermal properties of the package, the maximum power should be calculated that can be dissipated within the
device and still ensure operation remains within the recommended operating temperature range. The cell
balancing configuration can then be determined such that the device power remains below this level by limiting
the maximum number of cells that can be balanced simultaneously, or by reducing the balancing current of each
cell by appropriate selection of the external resistance in series with each cell.
16 Application and Implementation
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.
16.1 Application Information
The BQ769142 device can be used with 3-series to 14-series battery packs, supporting a top-of-stack voltage
ranging from 5 V up to 80 V. To design and implement a comprehensive set of parameters for a specific battery
pack, during development the user can use Battery Management Studio (BQSTUDIO), which is a graphical user-
interface tool installed on a PC. Via BQSTUDIO, the device can be configured for specific application
requirements during development once the system parameters, such as fault trigger thresholds for protection,
enable, or disable of certain features for operation, configuration of cells, and more are known. This results in a
"golden image" of settings, which can then be programmed into the device registers or OTP memory.
16.2 Typical Applications
Figure 16-1
shows a simplified application schematic for a 14-series battery pack, using the BQ769142 together
with an external secondary protector, a host microcontroller, and a communications transceiver. This
configuration uses CHG and DSG FETs in series, together with high-side PFET devices used to implement
precharge and predischarge functionality. See the following implementation considerations:
•
The external NPN BJT used for the REGIN preregulator can be configured with its collector routed either to
the cell battery stack or the middle of the protection FETs.
•
A diode is recommended in the drain circuit of the external NPN BJT, which avoids reverse current flow from
the BREG pin through the BJT base to collector in the event of a pack short circuit. This diode can be a
Schottky diode if low voltage pack operation is needed, or a conventional diode can be used otherwise.
•
A series diode is recommended at the BAT pin, together with a capacitor from the pin to VSS. These
components allow the device to continue operating for a short time when a pack short circuit occurs, which
may cause the PACK+ and top-of-stack voltages to drop to approximately 0 V. In this case, the diode
prevents the BAT pin from being pulled low with the stack, and the device will continue to operate, drawing
current from the capacitor. Generally operation is only required for a short time, until the device detects the
short circuit event and disables the DSG FET. A Schottky diode can be used if low voltage pack operation is
needed, or a conventional diode can be used otherwise.
•
The diode in the BAT connection and the diode in the BJT collector should not be shared, since then the
REG0 circuit might discharge the capacitor on BAT too quickly during a short circuit event.
Copyright © 2021 Texas Instruments Incorporated
Note
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BQ769142
SLUSE91A – SEPTEMBER 2020 – REVISED FEBRUARY 2021
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