TPS25751: TPS25751EVM + Bq25756EVM Power Path for PDO 1 PP3 Source Issue

Part Number: TPS25751

Tool/software:

Hi Everyone,

I already mention about the problem in here.

 RE: TPS25751: TPS25751EVM + Bq25756EVM Power Path for PDO 1 PP1 and PP3 Source Issue 

I used good boost converter for the supply DRV_SUP and PP5V from 1 Cell application. TPS25751 goes into hiccup mode since the switching sequence and PP5V supply to the VBUS was not managed well in my opinion.

Please check the attachment report which is in detail information about the setup, settings and oscilloscope SS.

I need to find how I will fix this problem. The aim is that use 5V generated from boost converter from 1 cell with limited current 500mA for PP5V connection. I want to supply for 5V/3A source VBUS from PP3.

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Problem Detail 11092025.pdf

  • Hello,

    Thank you for the detailed report.  I have also reached out to the BQ team regarding why the 4.7V on DV_SUP works but 5.0V does not.  

    Regards,

    Chris

  • Hello,

        Do you have the ability to increase the capacitance on the DRV_SUP and also retest with the LDO replaced with a stronger 5V to see if the issue is with the DRV_SUP.

        Also, in the 5V case (vs the 4.7V) do you see anything from the PD controller writing to the BQ?  I am curious in the transition from PP5V to PPHV if the PD thinks there is a reverse current event and the 4.7V does not trigger.

    Regards,

    Chris

  • Hi Chris,

    I’m using programable psu 4.7V or 5V supply. I also dont see any dropout in the oscilloscope. I draws 30ma to 300ma. No dropout also in the ldo 3.3v.

    I will sniff Monday morning between bq and pd update in here. Actually the main problem in my opinion is that pd enable vbus before not the enable switching on bq. It cause immediate drops on the vbus then bq sense the vac drops (most probably short circuit or overload) pd goes into the hiccup mode.

    Why 4.7v not effected this situation, it might be usb pd protocol don’t allow the enable vbus since the uvp. When the transection is finished vbus supply coming from bq 5v pd on the vbus enabled.

    is it possible such a this scenario? Is it possible to setup and test it with 1cell with nominal 3.2v? Do you have facilities to simulate in your lab?