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BQ25700A: Peak Power Mode

Dylan Zheng
Intellectual 1815 points
Part Number: BQ25700A
Other Parts Discussed in Thread: BQ25710

Dear all,

 I have some questions about  peak power mode to be confirm. The peak power mode can be trigger by input current or system voltage. I find when VBAT>VSYS_MIN, the peak power mode only can be trigger by input current. Am I right? And it seem to be related with IDCHG? If IDCHG is too small, it can not be trigger. What is the threshold of IDCHG?

When VBAT<VSYS_MIN, the peak power mode only can be trigger by system voltage. And what is the threshold of VSYS to trigger peak power mode?

Would you please introduce some detail information about using this mode?

Thanks!

  • 0
    TI__Expert 5330 points
    Hi Dylan,

    My interpretation of datasheet section 9.3.8 is that, when two-level ILIM (peak power mode) is enabled, the ILIM1, will be employed and will limit input current by reducing charging current.

    With single-level ILIM, battery will start to discharge once the system starts to draw more than 100% of ILIM1. However, with the two-level ILIM enabled, BQ25710 will allow the input current to temporarily go as high as ILIM2 instead of allowing the battery to begin discharging.

    Without a battery attached, the VSYS will begin to drop once the system draws more than ILIM1, and this will trigger the peak power mode.

    So perhaps a more succinct description would be that the peak power mode should be triggered whenever ISYS > ILIM1.

    It appears to me that your first scope capture demonstrates peak power mode and that your second scope capture does not, although it seems in the second capture that the battery is either not discharging or is discharging at a very low rate. I would suspect that if you increase ISYS in the second experiment, you would see the peak power mode employed.

    If this is different than what you are seeing, please give me the exact ISYS load you are applying, and the values of V_IN, VBATT and the values set for ILIM1 and ILIM2 (or better yet the full register dump) and I will attempt to recreate on Monday.

    Regards,
    Steve
  • 0 in reply to Steve Preissig
    TI__Intellectual 1815 points
    Hi Steve,
    You are right. Increase ISYS in the second experiment, the peak power mode can be triggered. The VIN=12V, VBATT=8.2V, ILIM1=1A, ILIM2=1.5A, When ISYS step to 1.5A in the second experiment, it can not be triggered. When ISYS step to above 1.8A , it can be triggered.