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TUSB321AI: Some question and schematic review

Jeff YANG
Mastermind 8735 points

Part Number: TUSB321AI
Other Parts Discussed in Thread: TUSB321

Hi,

1.ID Pin Functionality: Is the ID pin of the TUSB321 used to notify the system of its current operating mode (DFP, DRP, or UFP)? The datasheet mentions that when the TUSB321 is configured as a DFP or DRP, it pulls the ID pin Low to notify the Application Processor (CPU, PCH, or EC). Does the ID pin also pull Low when the device is operating in UFP mode?

2.Power Enable Logic: I noticed that the EVM uses the ID pin as the Type-C Power Enable signal, which is active-low. In DFP mode, the TUSB321 acts as a Host and provides power to the Device. However, in UFP mode, the TUSB321 becomes the Device itself. In this case, should the Power Enable be disabled? Could you please confirm if this is the correct logic? We are currently standardizing our circuit to DRP (supporting both DFP and UFP compatibility).

3.VBUS_DET Configuration: The datasheet suggests leaving VBUS_DET as NC (No Connect) for DFP mode, but recommends a 900kohm pull-up to VBUS for UFP and DRP modes. If I configure the device as a DRP, will the 900kohm pull-up resistor negatively impact the system when the TUSB321 is specifically operating in DFP mode?

Schematic:

TUSB321.png

  • 0
    Mastermind 8735 points

    Hi,

    Please also help reveiw the schematic as above. thanks!

    Jeff

  • 0 in reply to Jeff YANG
    TI__Guru 55676 points

    Hi Jeff,

    I will review the schematic and questions and get back to you shortly.

  • 0 in reply to Vishesh Pithadiya
    TI__Guru 55676 points

    Hi,

    Jeff YANG said:
    1.ID Pin Functionality: Is the ID pin of the TUSB321 used to notify the system of its current operating mode (DFP, DRP, or UFP)? The datasheet mentions that when the TUSB321 is configured as a DFP or DRP, it pulls the ID pin Low to notify the Application Processor (CPU, PCH, or EC). Does the ID pin also pull Low when the device is operating in UFP mode?

    The ID pin is used to determine if a downstream connection has taken place. The ID pin is only used in DFP and DRP modes. IS pin not used in UFP mode.

    If a downstream UFP is connected to the USB Type-C connector the ID pin will be set to low, and the SoC/ Vbus switch will use this signal as a trigger to deliver Vbus.

    Jeff YANG said:
    2.Power Enable Logic: I noticed that the EVM uses the ID pin as the Type-C Power Enable signal, which is active-low. In DFP mode, the TUSB321 acts as a Host and provides power to the Device. However, in UFP mode, the TUSB321 becomes the Device itself. In this case, should the Power Enable be disabled? Could you please confirm if this is the correct logic? We are currently standardizing our circuit to DRP (supporting both DFP and UFP compatibility).

    If in UFP mode the ID pin will not have a function. in UFP mode the device will be a power sink not a power source. Yes the logic is correct.

    Jeff YANG said:
    3.VBUS_DET Configuration: The datasheet suggests leaving VBUS_DET as NC (No Connect) for DFP mode, but recommends a 900kohm pull-up to VBUS for UFP and DRP modes. If I configure the device as a DRP, will the 900kohm pull-up resistor negatively impact the system when the TUSB321 is specifically operating in DFP mode?

    The 900k PUP is required in DRP mode as its needed for UFP operation. Having the 900k PUP on VBUS_DET will not affect DFP functionality.

  • 0 in reply to Vishesh Pithadiya
    TI__Guru 55676 points

    I will have the schematic reviewed in 1-2 business days.

  • 0 in reply to Vishesh Pithadiya
    Mastermind 8735 points

    Hi Vishesh,

    Please find the updated circuit below. Since our application operates in DRP (Dual Role Port) mode—acting as both Host and Device—that is why we are inquiring about the capacitance requirements.

    TUSB321AI.pdf

    I noticed the reference design places 150µF on the VBUS switch input and 10µF on the output. Is this configuration intended to support both DFP (Downstream Facing Port) and UFP (Upstream Facing Port) modes?

    My understanding is that the USB-IF specifies capacitance for the Host/Source side, likely to manage inrush current.

    Thanks!

    Jeff

  • 0 in reply to Jeff YANG
    TI__Guru 55676 points

    Hi,

    Here is the schematic review:

    1/2) CC1 & CC2: From pin of TUSB321 to USB Type-C connector. (May wan to add ESD protection here).

    3) CURRENT_MODE: 10K PUP to 5V. (5V 3A mode), OK

    4) PORT: PUP and PDOWN options, Floating (DRP mode), OK

    5) VBUS_DET: 910K PUP to VBUS, OK

    6) VCONN_FAULT: 200k PUP for open drain. May want to add test point to probe this signal. 

    7/8) OUT1 & OUT2: 200k PUP for open drain. May want to add test point to probe this signal. This is how current mode is transmitted to USB sink in UFP mode.

    9) ID: 200k PUP for open drain. Through inverter to EN pin of DIODES_AP22615AWU-7. OK

    10) GND: GND, OK

    11) DIR:  200k PUP for open drain. From pin of TUSB321 to SEL pin of PI3DBS16212ZBBEX. May need stronger PUP, see figure 3 in datasheet.

    12: VDD: 1x 100nF, 1x 4.7uF. OK

  • +1 in reply to Vishesh Pithadiya
    TI__Guru 55676 points
    Jeff YANG said:

    I noticed the reference design places 150µF on the VBUS switch input and 10µF on the output. Is this configuration intended to support both DFP (Downstream Facing Port) and UFP (Upstream Facing Port) modes?

    My understanding is that the USB-IF specifies capacitance for the Host/Source side, likely to manage inrush current.

    Yes its to help with inrush as well as provide filtering on Vbus to minimize pk2pk ripple and steady state noise. 

  • 0 in reply to Vishesh Pithadiya
    Mastermind 8735 points

    Hi Vishesh,

    thanks for your support.

    Jeff