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TPS25750EVM: Power bank application with TPS25750 and BQ25731

Guru 28665 points
Part Number: TPS25750EVM
Other Parts Discussed in Thread: BQ25731, TPS25750, USB-PD-CHG-EVM-01,

Hi Team,

My customer considers designing a Power bank (battery) application with TPS25750 and BQ25731.
Regarding the following E2E thread, there is the following comment.
https://e2e.ti.com/support/interface-group/interface/f/interface-forum/994386/tps25750evm-how-does-bq25731-terminate-charging-when-the-external-battery-is-used/3691235#3691235
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The TPS25750EVM only supports on on board emulated battery.  If you want to actually connect a board to an external battery, then you should use the USB-PD-CHG-EVM-01.
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According to the comment above, I understand BQ25731 shouldn't be controlled by TPS25750 but should be controlled by an external MCU for the application.
In other words, I2C line shouldn't be connected between TPS25750 and BQ25731.
Is my understanding correct?

Best Regards,
Yaita

  • Yaita,

    The TPS25750 cannot monitor the current and voltage of the BQ25731 to complete the charge termination function, so this feature has to be completed by an outside device

    It does have the ability to configure the BQ25731 to the correct output voltage and current limit when it is used to provide power to the type C connector in DFP mode.  It can also set the charge voltage and current for battery charging based on the type C PDO information when it is used as a UFP..

    It is possible to have the external MCU complete all required tasks for all modes and connect the I2C port of the TPS25731 and the I2CS port of the TPS25750 to the MCU, or it is possible to connect the I2Cm port of the TPS25750 to the I2C port of the BQ25731 I2C port and then connect the MCU up to the I2Cs port of the TPS25750.  With this configuration, you can use the I2CW and I2CR commands to update the BQ25731

    Regards,

    Chuck

  • Hi Chuck-san,

    Thank you for your reply.

    If we can achieve the charge termination function with TPS25750EVM and TPS25750 Application customization tool, I think it is the best way to design for my customer because external MCU isn't required.
    I heard we can terminate charging with pin control (not I2C access) of BQ27531 as the following. 
    https://e2e.ti.com/support/power-management-group/power-management/f/power-management-forum/999851/bq25731-terminates-charging
    I assume to set an external charge current monitor to control ILIM_HIZ pin of BQ25731 in this case.

    Do you think it is a reasonable way to design a Power bank (battery) application?
    What do you think of the suggestion?

    Best Regards,
    Yaita

  • Yaita-san,

    The TPS25750 does not have the required capabilities to execute charge termination of the BQ25731.  It will require an external MCU to execute the charge termination.

    It is possible to move the Boot function from the EEPROM into the MCU to save some of the additional cost.

    Regards,

    Chuck