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BQ25896: Periodic low pulse problem

Part Number: BQ25896

Hi Sir,

Our customers using BQ25896 for their tablet product, and encountered a problem that a low pulse will occured with a period of about 40s. By checking the data sheet, we found that this problem is caused by the default 40s watchdog timeout, and there will be no such problem when we turn off the watchdog.

But we cannot turn off the watchdog in actual applications. So we are trying to set an interval of 10s to check the watchdog timeout time, but it does not take effect. Can u give us some suggestion for this problem?

The charging waveform is shown as below:


Best Regards

  • Hi,

    Referring to 9.3.1 Host Mode and Default Mode, in order to keep the device register settings unchanged in host mode, the host has to reset the watchdog timer by writing 1 to WD_RST bit before the watchdog timer expires (WATCHDOG_FAULT bit is set).



  • Hi Ning,

    Thanks a lot. We have solved this problem from your suggestion. But now we encounter a new problem, that is, when there is no battery, the output of VSYS is normally. At this time, a load is added to the VBUS terminal (OTG function), and the system load on the VSYS output is powered off. By grabbing In the waveform, we learned that the increased load pulls down the voltage of the input terminal VBUS, and the low voltage sometimes reaches 3.5V -4.15V, which is lower than the normal operating voltage of BQ25896.

    The waveform of VBUS is as follows:

    For this problem, we have two question as follows:

    1) When the load is increased without changing the hardware design, can the output of BQ25896 still be able to load normally? Can this problem be solved through software settings?

    2) When the input voltage of VBUS drops below 3.9V, will the output voltage of VSYS also drop instantly? 


    Kind Regards