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TPS65988DK: is not negotiate for higher PDO. Need help to review schematic.

Yashodha Salgado
Prodigy 110 points
Part Number: TPS65988DK
Other Parts Discussed in Thread: TPS65988

Hi all,

I'm using TPS65988 in my custom PCB. Port 1 is only for the sink and the other one can act as a sink and source port. 

In my custom PCB I disabled the flash booting and selected config 5 with ADC1 resistor settings. But I don't see that VBUS is negotiated for more than 5V. It's always 5V. 

But when doing similar settings for TPS65988 EVM it reaches 12V (12V is my PD charger maximum). 

As I observed, LDO_3V3 and LDO_1V8 voltage are correct. Also, I could see CC communication through an oscilloscope (screenshot attached)


So, I need help to debug my circuit. I've attached my schematic herewith. Please somebody help me to review my schematic.

Thanks

  • 0
    TI__Genius 10772 points

    Hi Yashodha,

    • Can you tell me which solder bridge is populated that you are currently using on the ADCIN1 pins? Based on your configuration it looks like you should be using SB3, but want to make sure.
    • When you test TP1 and TP4, what do those result in? Or can you get captures of these? As well can you capture VSYS and VBUS if possible? As it may be an issue with the external power path. In the above scope shot, can you tell me what is each signal?
    • Do you have a PD Analyzer you could use to check the contract negotiations? 
    • You may be trying to source as the source for Configuration 5 is limited to the 5V and could explain why you never see higher. But you may be sinking or trying to.

    Could you look into getting the above captures?

    Thanks,
    Field

  • 0 in reply to Field Tolson
    Prodigy 110 points

    Hi Field,

    1. Yes. it is SB3

    2. about TP1 and TP4, I'll check and update you soon.

    3. VSYS and VBUS both are around 5V

    4. Above scope shot, purple color: CC line, Yellow color: VBUS

    5. Yeah, I have PD analyzer. please check the following SS. 

    Please check these

    Thanks

  • 0 in reply to Yashodha Salgado
    TI__Genius 10772 points

    Hi Yashodha,

    1. And you are trying to sink or source when this is occurring?

    2. Please and thank you.

    3. Is it possible for you to also provide a capture of PB_VAR_DCDC or PB_PP_HV? It may be helpful to look at this and the PP_HV1 and PP_HV2.

    5. Do the source capabilities display any contract >5V?

    Thanks,
    Field

  • 0 in reply to Field Tolson
    Prodigy 35 points

    Hi, I am assisting with this issue. Seems that the PDO for Configuration 5 is a variable fixed 5-20v and seems that the TPS65988 never requests for a higher-voltage contract.  Not sure why this is different than the EVM, but after changing the firmware on the TPS65988 to and different PDO, it now works fine.