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TPS65987D: tablet PC of a specific manufacturer

R.Fukunaga
Expert 2625 points
Part Number: TPS65987D


Tool/software:

Hi all,

The following behavior can be seen when connecting a tablet PC of a specific manufacturer whose battery has been discharged.

VBUS output stops repeatedly

->Complete stop after a while

->The tablet PC cannot be charged

When my customer checked the signal,

they found that after CC1 terminal exchanges commands about 5 times, the CC1 voltage rises, and then the VBUS output stops.

Could you tell me what causes this behavior?

Best Regards,

Ryusuke

  • 0
    TI__Guru 66031 points

    Hello,

    There could be a number of reasons for the behavior.

    (1) VBUS drops because of the inrush of the dead battery condition.

    (2) Source is only sending source capabilities message 5 times and then stops sending.  If the PD on the PC is still 'booting', ie because of dead battery PD configuration was never loaded the PD will issue a reset because of sink timer timeout.

    (3) The system is not designed to support dead battery.

    You may want to confirm that the issue is not related to the source by attempting with different kinds of sources.

    Regards,

    Chris

  • 0 in reply to Chris Sterzik
    Expert 2625 points

    Hi Chris,

    I send the waveforms below.

    As CC1 has sent the command about 5 times, I am aware that (2) mentioned is most likely the cause.

    Could you please check the waveform and give me your opinion?
    If you have a waveform when the battery is not connected, I would appreciate it if you could share it with me.

    Best Regards,

    Ryusuke

  • 0 in reply to R.Fukunaga
    TI__Guru 66031 points

    Hello,

    R.Fukunaga said:
    Could you please check the waveform and give me your opinion?

    The waveform does not provide any information about the state of the PD controller in question. I am not clear if you are debugging the tablet PC or the source.  Can you confirm?  Which device do you believe is operating badly?

    The waveform below is with the logic analyzer tool.  This is with the Power DUO EVM.  Please note that the source is sending source capabilities multiple times.

    Regards,

    Chris

  • 0 in reply to Chris Sterzik
    Expert 2625 points

    Hi Chris,

    Thank you for your reply.

    My customer used avhzy CT-3 to get PD command.

    From this communication log, I understand that there is no response from Sink and negotiation is not done correctly.

    1) Is it correct? I would appreciate it if you could give me any comments.

    Also, regarding the tablet where the problem occurred, 

    The problem occurred only in the tablet of a specific manufacturer.

    I was able to charge 2 tablets that were discharged by different manufacturers (I think they don't have PD function).

    I was able to charge the tablet in question with Anker's PD charger.

    I was not able to charge the tablet in question with Thunderbolt laptop.

    2) Based on these, I think the cause is not conforming to USB PD specification.(See E2E below)

    Is it correct?

    (+) TPS65987D: TPS65987 status - Power management forum - Power management - TI E2E support forums

    Best Regards,

    Ryusuke

  • 0 in reply to R.Fukunaga
    TI__Guru 66031 points

    Hello,

    R.Fukunaga said:
    1) Is it correct? I would appreciate it if you could give me any comments.

    Yes.  This is correct.

    R.Fukunaga said:
    The problem occurred only in the tablet of a specific manufacturer.

    Does the tablet expect/prefer BC1.2 or some other charging protocol over D+/-?  

    R.Fukunaga said:
    I was able to charge the tablet in question with Anker's PD charger.

    The Anker is a source only while the labtop is dual role power (DRP).  If the Tablet is truely in a dead battery state, then i would not expect the tablet to send TRY.SRC.  Also, to the previous point does the Anker support the BC1.2 or other protocols?

    R.Fukunaga said:

    2) Based on these, I think the cause is not conforming to USB PD specification.(See E2E below)

    Is it correct?

    Yes.  I believe so, but this would suggest that the USBC specification is also not supported. 

    Regards,
    Chris