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TUSB321AI: TUSB321AI + HD3SS3212 for UFP application

K.Yaita
Guru 29720 points
Part Number: TUSB321AI
Other Parts Discussed in Thread: HD3SS3212, TUSB321

Hi Team,

My customer considers to use TUSB321AI + HD3SS3212 for UFP application.
Although the following schematic is for DFP application, is VBUS switch required for UFP application?



If the answer is yes, I would like to know how to control EN pin of VBUS switch for UFP application.
My customer wants to know it.

Best Regards,
Yaita / Japan disty

  • 0
    TI__Mastermind 36085 points

    Hello Yaita-san,

    The switch is not required for UFP applications, just make sure the VBUS_DET pin is connected to the VBUS signal thru the 900K resistor and configure the PORT in with a pull-down resistor.

    Regards,

    Diego.

  • 0 in reply to Diego Cortes
    Guru 29720 points

    Hi Diego-san,

    Thank you for your reply.

    Figure 3 (DFP mode schematic) shows ID pin of TUSB321A is pull-up and connected to OEn pin of HD3SS3212.
    TUSB321A datasheet shows ID pin is still Hi-Z when port is UFP as the following.



    I believe OEn pin should be controlled to Low (enable HD3SS3212).
    Should I also disconnect ID pin to OEn pin and pull-down OEn pin for UFP application?

    Best Regards,
    Yaita 

  • 0 in reply to K.Yaita
    TI__Mastermind 36085 points

    Hi Yaita-san,

        That's correct, the ID pin will go LOW only when the TUSB321 is connected as DFP, also the DFP application enables the MUX only when there is a DFP connection. That's expected. For UFP application you can control  OEnby using an external controller that is monitoring the TUSB321's OUT pins (if any OUT pin is low). The behavior is the following:

    MODE OUT1 OUT2
    Unattached HIGH HIGH
    Attached - 900mA HIGH LOW
    Attached - 1.5A LOW HIGH
    Attached - 3A LOW LOW

    Another option is fo leave OEn always ON.

    Regards,

    Diego.