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TUSB216-Q1: BC1.2 function abnormal

Dongbao Zhou
Expert 3960 points
Part Number: TUSB216-Q1
Other Parts Discussed in Thread: TUSB216, TUSB217A

hello expert,

For TUSB216-Q1 BC1.2 CDP function, if CDP_ENZ=L, VCC is stable, what are the possible reasons of fail BC1.2 handshake?

We found the if CD pin is asserted earlier than BC1.2 handshake (because SOC is configure as device mode instead of host), BC1.2 handshake will fail and a reset will help solve the problem.

May you help explain why this happens?

Dongbao

  • 0
    TI__Genius 17505 points

    Hi Dongbao,

    You are saying that in Host mode, the device acts properly at start-up, but in Device mode, the device needs to be reset after power-up to re-trigger the BC1.2 Handshake, correct?

    Going by the pictures you sent, it seems like the issue is stemming from the CD Pin being asserted at start-up, as it functions correctly as when the SOC is set in host mode and the CD pin is not asserted at start-up. Do you have any means of seeing if you see the same results in device mode if the CD pin is not asserted at start-up? I will check internally and see I can find more information regarding this behavior and get an answer back to you tomorrow.

    Also, if you could send the schematics surrounding the TUSB216, I would appreciate it.

    Thanks,

    Ryan

  • 0 in reply to Ryan Kitto
    TI__Expert 3960 points

    hi Ryan,

    You are correct.

    From the datasheet description, BC1.2 function shall independent of the EQ compensation.

    I am working on with customer to check whether a reset after the SOC side change from HOST to DEVICE mode helps solve the BC1.2 handshake issue, as the test results is not stable yet.

    Dongbao

  • 0 in reply to Ryan Kitto
    TI__Expert 3960 points

    Here are the soc host-device-host-device change CD/D+/D- waveforms, two odd thing

    1. Once CD is asset in device mode, TUSB216 is enable to start EQ compensation with 1kHz waveform even mobile phone is not connected.

    2.  CD not back to 0 seems because the compensation signal, it's confirmed that once disable tusb216, d+/- is 0V.

  • +1 in reply to Dongbao Zhou
    TI__Genius 17505 points

    Hi Dongbao,

    Dongbao Zhou said:
    e2e.ti.com/.../quote]

    This thread is correct, and I believe it is valid for the TUSB216/I.

    It is noted in the TUSB217A datasheet that the TUSB216 only has CDP functionality, meaning the BC1.2 Controller should only be enabled when the device is being used in host mode, charging a downstream device. As such, when set for device mode, I do not believe there is any available BC1.2 functionality.

    The TUSB217A, however, should be capable of both host and device mode BC1.2 functionality.

    Please let me know if you have any other questions.

    Thanks,

    Ryan