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HD3SS3220: UFP mode AC coupling capacitor

Giacomo_Angiolini
Prodigy 20 points

Part Number: HD3SS3220

Hi all,

I'm designing an FPGA board which implements USB type-C connection.
I've chosen to use HD3SS3220 MUX/controller (configured as UFP) since my USB (device) controller supports only USB 3.0.
I've no other devices in between, so: FPGA <-> USB device controller <-> HD3SS3220 <-> USB type-C connector <-> PC/host


With reference to SLLU241A schematics on page 7, my question is: do I only need to put AC coupling capacitors (100nF) on SSTX+/- lines on the host side (pin 21,20 and 17,16), without pulldown on device side (pin 6,7)?
Moreover, do I need coupling capacitors and pull-downs on SSRX+/- lines on device side (pin 9,10)? Or they're only needed if bias from my USB device controller is above 2V?

I've already read most of the previous forum posts and the reference designs on the topic, but I would like to have a confirmation.

Thank you in advance for the replies

  • 0
    TI__Guru**** 187671 points

    Do I only need to put AC coupling capacitors (100nF) on SSTX+/- lines on the host side (pin 21,20 and 17,16), without pulldown on device side (pin 6,7)?

    *** You do need AC coupling caps (100nF) on SSTX+/- lines on the host side (pin 16, 17, 20, and 21)

    *** The pulldown resistors help to reduce the discharge time to be within the spec limit of 250 ms. The resistors are optional assuming leakage current from external components is enough to discharge capacitor.  

    Do I need coupling capacitors and pull-downs on SSRX+/- lines on device side (pin 9,10)

    *** This is optional since the corresponding TX should have 100nF AC coupling caps. If needed, please use 330nF on SSRX+/-.

    Thanks
    David

  • 0 in reply to David (ASIC) Liu
    Prodigy 20 points

    Hi David,

    thank you for your reply!