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TPS25750EVM: CC negosiation is failed when Micro USB is connected

teritama
Expert 2155 points
Part Number: TPS25750EVM
Other Parts Discussed in Thread: TPS25750, TPS25751, , TPS25751EVM

Tool/software:

Hi team,

Our customer currently evaluating the TPS25750 and have encountered an issue during testing. When a Micro USB connection is present and a Type-C PD adapter is connected to the TPS25750, the CC negotiation does not occur. Additionally, when the adapter is disconnected, approximately 2V remains on the VBUS line. However, if VBUS is manually discharged to 0V, the adapter can then successfully provide power with correct CC negotiation upon reconnection.
In this time, there is no load.

Could you please let me know:

・Have there been any known cases where CC negotiation fails under these conditions?
・Is it expected behavior for VBUS to retain around 2V after the adapter is removed?


Any insights or documentation related to this behavior would be greatly appreciated.

Best regards,

teritama

  • 0
    TI__Mastermind 37855 points

    Hi Teritama,

    No new designs should be evalutating the TPS25750. Please move to the TPS25751 at your soonest convenience. The TPS25751 is the direct p2p successor to the TPS25750 with added features, the latest support, and will support the latest PD spec (where the TPS25750 will not)

    teritama said:
    When a Micro USB connection is present and a Type-C PD adapter is connected to the TPS25750, the CC negotiation does not occur. Additionally, when the adapter is disconnected, approximately 2V remains on the VBUS line. However, if VBUS is manually discharged to 0V, the adapter can then successfully provide power with correct CC negotiation upon reconnection.
    In this time, there is no load.

    Typically the microUSB should not affect the VBUS voltage, but it sounds like somehow there is some leakage between the micro-usb and VBUS paths. Part of the PD controllers control involves sensing "correct" voltages during different phases of connection and disconnection. Having 2-V sitting on VBUS would affect the ability of the PD controller to connect when it expects 0-V during a disconnected state.

    teritama said:
    ・Have there been any known cases where CC negotiation fails under these conditions?

    This is not surprising, but I have not seen this "micro-usb feeding voltage to VBUS" issue on the TPS25750EVM myself.

    teritama said:
    ・Is it expected behavior for VBUS to retain around 2V after the adapter is removed?

    No

    Unfortunately, your best option would be to use the EVM without the micro-usb connected.

    The main thing is that the customer should not be using or evaluating this part to begin with as it is NRND, and the TPS25751 and TPS25751EVM should be used and evaluated instead.

    Thanks and Regards,

    Chris

  • 0 in reply to Christopher Lim1
    Expert 2155 points

    Hi Chris-san,


    Sorry for my reply delay.

    The customer says that when push S2 on the EVM that is TIVA's RESET switch, the voltage of LDO_3V3 is decrease to 0V and after few second, VBUS become 0V.

    In my expect, this means LDO_3V3 is connected to F_SYS_3V3 that is output of TPS76833.

    I want to know that if other 3.3V is supplied to LDO_3V3, is it possible that LDO_3V3 path become current path to VBUS like below?

    Best regards,

    teritama

  • 0 in reply to teritama
    TI__Mastermind 37855 points

    Hi Teritama,

    Voltage should never be applied to LDO3V3. It is an internal power supply generated by the device.

    teritama said:
    In my expect, this means LDO_3V3 is connected to F_SYS_3V3 that is output of TPS76833.

    From what I see on the schematic, F_SYS_3V3 is only connected to teh S2 pin and to the ICD_TCK and ICD_TMS nodes. It does not appear to have any connection to LDO3V3.

    Unless the EVM was damaged in some way, I don't see any obvious connections between the F_VBUS power and the Type-C VBUS and LDO3V3 pins.

    Is the customer able to evaluate the EVM with the micro-usb disconnected? It should not be required to see the TPS25750 standalone behavior.

    When trying to replicate this issue on an EVM, I do not see any voltage on VBUS appearing or disappearing when the micro-usb port is connected and disconnected. It stays at a constant 0-V.

    Thanks and Regards,

    Chris