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TPS65982 EVM repeats reset when 2.5A load was addes.

msmn
Intellectual 805 points
Other Parts Discussed in Thread: TPS65982

Our customer saw the follwoing behavior.

TPS65982 EVM (Config_ID:6) with AC adapter <--type c--> TPS65982 EVM (Config_ID:5) without AC adapter

1. Added 2.5A-load to TPS65982 EVM (Config_ID:5).

2. Attached TPS65982 EVM (Config_ID:5) to TPS65982 EVM (Config_ID:6).

3. Blinking LEDs. It looked like that reset was repeated.

They asked me why the reset was repeated. 

That's because TPS65982 EVM (Config_ID:5) drew 2.5A before the UFP/DFP connection was established, I think.

Is my understanding correct?

Regards

msmn

Provider Config_ID:6

Consumer [B2:B0]=[101] Config_ID:5

  • 0
    TI__Expert 3625 points

    Hi msmn,

    Thank you for your question.

    Where did you apply the 2.5A to VBUS or to the SInk Path? Is this load a consistent 2.5A or does it initially spike and settle out at 2.5A? If it is the the second case your load could be tripping the TPS65982's current protection and shutting it off (hence the reset you may be seeing).

    Additionally, can you provide an oscilloscope shot of VBUS, CC1 and CC2 as you apply the load and connect the powered EVM (charger adapter Config 6) to the unpowered EVM with 2.5A load (dock Config 5)? This may help us to find out when the reset occurs (at initial connect, 5V, during the PD contract, or wherever).

    Regards,
    Karl

  • 0 in reply to Karl Fleischmann
    Intellectual 805 points

    Karl,

    I attach 2 oscilloscope shots of VBUS, CC1, CC2 and current.

    2.5A or 2.7A load was applied to J6 on TPS65982 EVM.

    It worked fine for 2.5A load, however reset was repeated when 2.7A load was applied.

    Does the reset happen at the timing of PS_READY message?

    Please let me know your comment.

    Regards

    msmn

  • 0 in reply to msmn
    Intellectual 805 points
    karl,

    Could you answer this question?

    Regards
    msmn
  • 0 in reply to msmn
    Intellectual 805 points
    Karl,

    The customer needs your answer.

    Regards
    msmn
  • 0 in reply to msmn
    TI__Mastermind 30280 points

    msmn,

    Are you applying an analog load (resistors) or an electronic load?

    I cannot see because the resolution of your scope shot pictures is very low, but what is the voltage on VBUS?

    Is VBUS = 5V, 12V, or 20V?

    It sounds like you are applying the load before the TPS65982 is aware that there is about to be a Load.

    Have you tried the test by applying the load after the PD contract is negotiated?

    If you apply the load too early, it may be an accidental violation of the spec and could cause issues.