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Original question:

BQ25720: Hybrid power supply mode of BQ25720

BQ25720: Abnormal triggering SYSOVP

Lumina Gui
Genius 3660 points
Part Number: BQ25720

Tool/software:

Dear TI Engineer,

During our testing of BQ25720 charging we found that when the load is relatively large, the system voltage suddenly rises to 20V, triggering SYSOVP. The waveform is as below:

(The yellow is the upper MOS of EU1, the blue is the lower MOS of EU1, the red is the upper MOS of EU2, and the green is the system voltage VSYS)

From the first picture, it can be seen that at the beginning, the MOS of EU1 is working normally, the upper MOS of EU2 is conducting, and then the upper MOS of EU2 suddenly shuts down, and the system voltage starts to rise continuously.

At this time, the adapter output voltage is 20V, and the VSYS_min configuration is 12V. The value read from the 0X20 register is 0x8010, whic means the SYSVOP. The schematic is as below:

BQ25720_SCH.pdf

Can you help analyze the cause of this problem?

Thanks,

Kind Regards

  • 0
    Genius 3660 points

    Dear TI Engineer,

    Add some additional information:

    1) This problem occurs when the battery is about to be fully charged (approximately 90%) or in a fully charged state.

    2) The adapter is a PD3.0 adapter and can provide a maximum power of 20V/3.25A. During load testing, this problem occurs when the overall power exceeds 65W, but it has also occurred when the overall power is below 65W.

    3) We also captured the voltage waveforms of VCHG-IN(Yellow), SN-SOP(Blue), SN-SON(Red), and VSYS(Green) when this issue occurred, the details are as below:

    4) We also captured the waveforms of SW1 (Yellow), SW2 (Blue), and VSYS (Red) when this issue occurred.

    5) The 0x15h register is set to 0x44C0 (17.6V), and the values read from registers are 0x21=0x7000 and 0x20=0x8010.

    6) We also tried to add tantalum capacitors to the input and output terminals, but this problem still exists, it's just that the time when the problem occurred has been postponed.

    Thanks,

    Kind Regards

  • 0 in reply to Lumina Gui
    TI__Mastermind 33335 points

    Hi, Lumina,

    Thanks for the detailed waveforms. I think SYSOVP was triggered. We just need to understand why SYSOVP was triggered. 

    Our field support will reach out to you with more details. 

    Regards,

    Tiger