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BQ24800: plug in adapter in battery only boost mode

haifeng xu
Prodigy 20 points
Part Number: BQ24800

Hi, BQ24800 support team,

I'm seeing some confusing waves when I used BQ24800EVM，can you briefly describe the process for me? Thanks!

As the follow figure, I set BAT=6V (DC voltage source), Battery regulation 6.288V, SYSMIN 8.8V with 2.4V offset, working in battery only boost mode.

Then, plug in 21V adapter and I can see about 0.5A charge current  to battery (Charge current set 1A in register).

 So, Why are there 0.5A charge current when plug in adapter?

Thanks

Harvey

  • 0
    TI__Genius 11385 points

    Hi Harvey,

    Can you try it without a switch-over from battery only boost? For example, just do an adaptor plug in and then change the charge current?

    Charge current should default to 0A at POR.

    Thanks and I hope this helps,

    Peng

    *Please press "This Resolved My Issue" on the thread if my answer is satisfactory

  • 0 in reply to Pengzhao Zhu
    Prodigy 20 points

    Hi Peng,

    Thanks for your reply.

    Adapter plug in and then change current to enable charge, it`s ok.

    Can you briefly describe why are there about 0.5A charge current when plug in adapter in battery only boost mode?

     

  • 0 in reply to haifeng xu
    TI__Genius 11385 points

    Hi Haifeng,

    I tested and I don't see the issue.

    VIN~21V
    VBAT~6V
    Charge Voltage = 6288mV
    VSYS_MIN = 8832mV
    Boost Regulation Voltage = VSYS_MIN + 2.4V
    Charge Current = 1024 mA


    CH1 = VIN
    CH4 = IBAT

    It goes from sourcing current to sinking current at 1A.

    Recommend to check your setup. 

    Thanks and I hope this helps,

    Peng

    *Please press "This Resolved My Issue" on the thread if my answer is satisfactory

  • 0 in reply to Pengzhao Zhu
    Prodigy 20 points

    Hi Peng,

    Thanks again. 

    Before your plug in adapter, it`s working in battery only boost mode? 

    I've checked my setup again, and the question is still as shown in first picture. After plug in adapter, it will still switch for about 12ms before exit battery only boost mode. During this time (12ms), discharge current (boost mode) will change to charge current.

    The following figure can also be proved.

    Thanks & Best regards!

  • 0 in reply to haifeng xu
    TI__Genius 11385 points

    Hi Haifeng,

    Yes battery only boost mode was active when I plug in the input power supply. By the way, I do not recommend using a DC power supply at the battery pin as most DC power supply are not meant for sinking. Battery emulators and bi-directional power supplies are typically used.

    Thanks and I hope this helps,

    Peng

  • 0 in reply to Pengzhao Zhu
    Prodigy 20 points

    Hi Peng，

    Thanks for your advice. I`m parallel an electronic load with DC power supply to behave as a real battery.

    Can you zoom in the black part to 10ms/grid of your test result？ And show PHASE, SYSTEM, IBAT (or IL) and TB_STAT waves.

    Thanks & Best regards!

    Haifeng

  • 0 in reply to haifeng xu
    TI__Genius 11385 points

    Hi Haifeng,

    The charger will switch over from boost mode to charging mode when you plug in the adaptor. The waveform was captured when the device was in boost mode and adaptor plugged in.

    Thanks,

    Peng