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  • TI Thinks Resolved

HD3SS3220: DRP not consistently enumerating as a SS device

Prodigy 35 points

Replies: 5

Views: 58

Part Number: HD3SS3220

We have a custom product we have developed that is using a USB-C connector to implement a SS port.  The port is a DRP so additional circuitry has been added to support this feature aside from the HD3SS3220 switch.  In my design I'm using 100nF AC coupling caps on TX1/TX2 and RX1/RX2 lines.  However, I noticed some posts have suggested to use 220nF instead of the 100nF.  I also noticed another forum post suggested using 330nF coupling caps on the RX lines.  What is the correct values to utilize?  How are those values determined?  Could this be causing my issue?? Also I'd like to have someone review my schematic.  Is there an email address I can send my schematic sheet too.  

  • pls send your schematic with private message.

    normally RX should be 330nf, TX can be either 10nf or 220nf.

  • In reply to Brian Zhou:

    I've sent you the schematic in a private message.

    Is the TX value a typo?  Should it be 100nF not 10nF?

  • In reply to Jacqueline Flores:

    sorry,  TX should be 100nf.

    you only can have cap  on one side of MUX.

    on RX side, either 330nf or no cap.so C912, C927,C928,C929 need to be changed to 330nf.

    if you don't need Current_mode, lust leave it open or pullup to 5v, don't ground.

    what relationship between 5v, 3.3v and Vbus?

  • In reply to Brian Zhou:

    I'm using current mode to set the limit to 900mA when the DRP is in DFP mode.  This is why I have the current_mode signal tied to ground.  Is this incorrect?  

    The 5V is generated from an external DC jack.  This is the power source used when the device is in DFP mode.  The TPS66021 is used to switch the VBUS power on and off. I also sent you a message containing the schematic page with the dc input jack as well as the power switch we are using.  Either the DC jack, V5p0, or USBC_VBUS_SRC are used to generate the 3.3V.  This is controlled by the switch, TPS2121RUXT.  Please let me know your thoughts here. 

  • In reply to Jacqueline Flores:

    Current mode is correct.

    Since you are using both 3.3v and 1.8v, its better power up after 5v and off before 5v .

    Vbus is correct

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