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BQ25756: Operation without a connected battery

Ben
Intellectual 400 points
Part Number: BQ25756
Other Parts Discussed in Thread: BQSTUDIO, USB2ANY, EV2400

Tool/software:

Hello TI team.

I'm designing a BQ25756 charger board, and have a few questions.

1. Does it operate the charger IC only with power supplied from VAC (adapter source)  without a connected battery?

when I test using BQ25756 EVM, I can not read I2C data. If I miss setting point, please let me know.

2. Regarding the operation without a connected battery, according to the FAQ and EVM guide, it works but requires a 2000uF capacitor.

In my case, I have only 120uF capacitance at the output line. Is it possible to work?

Thank you.

  • 0
    TI__Mastermind 31145 points

    Hello Ben,

    I recommend setting EN_PFM=0 and EN_TERM=0 if you are operating without a connected battery.

    Ben said:
    In my case, I have only 120uF capacitance at the output line. Is it possible to work?

    What's your load here in this case?

    Ben said:
    when I test using BQ25756 EVM, I can not read I2C data. If I miss setting point, please let me know.

    What's your test setup here? Are you using the EV2400 with BQStudio or the USB2ANY with TI Charger GUI?

    Best Regards,
    Ethan Galloway

  • 0 in reply to Ethan Galloway
    Intellectual 400 points

    Hello Ethan

    My test setup

    - EVM : BQ25756 EVM https://www.ti.com/tool/BQ25756EVM

    - Input(J1) : Power supply (23V, 8A setting)

    - Battery(J3) : no connection

    - EV2400 communication kit, I2C to USB

    when I test using BQ25756 EVM, I can not read I2C data. (Device ack error)

    But, When I connect battery only, I can read I2C data using EV2400 tool.

    I want to know the BQ25756 is possible to operate with VAC source except battery.

    Thank you.

  • +1 in reply to Ben
    TI__Mastermind 31145 points

    Hello Ben,

    Thanks for the new information.

    Ben said:

    when I test using BQ25756 EVM, I can not read I2C data. (Device ack error)

    But, When I connect battery only, I can read I2C data using EV2400 tool.

    It should be possible to use I2C when only VAC is applied. When you only have VAC attached to the IC, can you measure the voltage on the VAC test point on the EVM?

    Best Regards,
    Ethan Galloway

  • 0 in reply to Ethan Galloway
    Intellectual 400 points

    Hello Ethan

    It works well, but I set the same condition than before..

    I think the output voltage swing means it repeatedly charges and discharges using an output capacitor.

    In this output voltage condition, can I set increasing the e-load? (Target : ~100Wmax)

    Thank you.