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TPS25751: Vbus unstable when acting as source

Pratham M
Prodigy 80 points
Part Number: TPS25751
Other Parts Discussed in Thread: BQ25798,

Hi there, We are using TPS25751 with BQ25798 charging IC. While the sink application works correctly. We are having issues with source capabilities where Vbus is not stable and keeps dropping to 0V when the PD device (Mobile Device) is attached with the port.

But when non-PD devices (Pendrive, SSD etc) are attached Vbus is stable.  

We are using the 1S battery configuration for BQ.

Here's our observations,

  1. When we configure the TPS25751 as source only from the gui tool (picture below). The Vbus is stable at 4.7V but we are getting around ~1.18A current instead of 3A.

        image.png

2. When we configure the TPS as sink and source both (picture below). The Vbus is unstable and keeps dropping to 0V when TPS acting as source with PD device(Mobile Phone) as sink. 

image.png

 

 

 

 

 

 

 

Can you tell what could be causing this issue? Is that some misconfiguration or some limitation we have missed? 

Best Regards,

Pratham

  • 0
    TI__Intellectual 1710 points

    Hello Pratham,

    Thank you for reaching out.

    I understand you are having trouble providing power from the TPS25751.

    1. Do you have a TI PD analyzer? If so, can you provide me with PD logs so I can look at the flow of the source negotiation occurring.
    2. Additionally, please inform me of the values at pins VIN3V3 and PP5V on the pd controller when sourcing? 
    3. Lastly, can you please send me the individual JSON files for the Source only and DRP configuration you are testing?

    Thank you,

    Katilynn