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HD3SS3220: AC Coupling Capacitors for SS signals

K.Yaita
Guru 29720 points
Part Number: HD3SS3220
Other Parts Discussed in Thread: 3220DFP-DGLEVM,

Hi Team,

The datasheet shows "75-200 nF range allowed" for AC Coupling Capacitors for SS signals (TX pairs).
On the other hand, 3220DFP-DGLEVM has 0.47uF each.

http://www.ti.com/lit/ug/sllu237a/sllu237a.pdf

Which is recommended value?

Best Regards,
Yaita

  • 0
    TI__Guru**** 182631 points
    Yaita-san

    There would be another set of capacitors (0.1 µF) in series with the USB TX path of the host system, so this will bring the total capacitance to 1/(1/0.1 + 1/0.47) = 82nF.

    But 0.47uF needs to be updated per the latest USB ECN. The latest ECN states the capacitor needs to be 0.297uF min and 0.363uF max. The typical value is 0.33uF.

    Thanks
    David
  • 0 in reply to David (ASIC) Liu
    Guru 29720 points

    Hi David-san,

    Thank you for your reply.

    >But 0.47uF needs to be updated per the latest USB ECN. The latest ECN states the capacitor needs to be 0.297uF min and 0.363uF max. The typical value is 0.33uF.
    I believe you referred ECN above is for RX path however the following C17,C19, C21, C22 are actually TX path as I pointed red squares in the following schematic.
    How should I consider it?



    Best Regards,
    Yaita

  • 0 in reply to K.Yaita
    TI__Guru**** 182631 points

    Yaita-san

    Please see the diagram below. HD3SS3220 is a switch, so even though it is connected to CTX[n]_P/N of the Type C receptacle, from Type A connector perspective, I still consider the signal to be RX.

    Thanks

    David