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HD3SS3212: Best placement for AC caps in DRP mode

d_zero
Genius 4775 points
Part Number: HD3SS3212
Other Parts Discussed in Thread: HD3SS3202

Dear *

I have few questions regarding the passive mux for USB 3 Gen2 and using Type-C connector

AC caps - in Datasheet there are multiple configuration but which one is recommended?

1) if our device is a DRP and can act as a source ( when USB key is attached to our device) or sink (when we attach our device to a PC), what is the recommended placement for AC caps ?

a) on TX PORT A between MUX and host/device?

b) on TX PORT B,C between MUX and the connector

2) if our device is a UFP , what is the recommended placement for AC caps ?

a) on TX PORT A between MUX and device?

b) on TX PORT B,C between MUX and the connector

3) Which passive MUX does TI recommend for NEW designs HD3SS3212 or HD3SS3202?

And can you tell why is HD3SS3212 better than HD3SS3202 or vice versa?

Best Regards,
David.

  • 0
    TI__Guru 64326 points

    Hi,

    HD3SS3212 has better performance than HD3SS3202 but both devices can be used for USB 3 Gen2 Type-C. The ultimate design decision is this, What do I want to bias my Type-C Mux (HD3SS3202/HD3SS3212)? I recommend that the Type-C Mux is always biased by the Host/controller for all applications because this value is generally known and maintained by Host/controller internally. In some cases biasing by the endpoint is preferred however in application where the  Type-C Mux is in between a connector and Host/controller and the biasing for the Type-C Mux comes from the connector, this value is unknown and could cause potential issues. 

  • 0 in reply to Malik Barton57
    Genius 4775 points

    Dear Malik,

    thank you for the replay.

    1) so whatever is the MUX configured as UFP, DFP or DRP it is better to bias the MUX from the HOST (DFP) or DEVICE (UFP) USB controller?

    2) please can you tell which parameters are better performance on HD3SS3212 than HD3SS3202, i see that the HD3SS3202 is a newer device ?

    3) so you recommend the HD3SS3212 (older part) for NEW DESIGNS?

    Best Regards,

    David.

  • 0 in reply to d_zero
    TI__Guru 64326 points

    Hi,

    1) It is generally better to bias from the Host (DFP/DRP). In some cases the Vcm may be incompatible between the two devices and AC coupling has to be used.

    2) Please refer to the electrical specifications of each datasheet and compare values such as Differential insertion loss. 

    3) Both devices are recommended for new designs. 

  • 0 in reply to Malik Barton57
    Genius 4775 points

    Hi Malik,

    i looked in datasheet for parameters on page 6.

    Please can you confirm that HD3SS3212 has better IL and RL, and HD3SS3202 has better Oirr and Xtalk @ 2.5G and 5G ?

    In previews post you said "HD3SS3212 has better performance than HD3SS3202" did you mean about the IL and RL, because the IL and RL are more important than Oirr and Xtalk?

  • 0 in reply to d_zero
    TI__Guru 64326 points

    Hi,

    In general, IL and RL are key parameters that should be considered when selecting your high speed mux. I would not say they are more important than Oirr and Xtalk. IL and RL help the designer to understand the effect of the signal as is passes though the high speed mux. Oirr and Xtalk help to describe the effect of one channels effect on other passing through the same device. My previous statement was referring to the IL and RL for HD3SS3212 however if you have a design in which you expect less losses through the other transmission media then HD3SS3202 is a viable option. 

  • 0 in reply to Malik Barton57
    TI__Guru 64326 points

    Is there any more support needed for this issue? If so please reply with any relevant details so that I can further assist you. For now I will be marking this thread as "TI Thinks Resolved". If you have resolved your issue, please post the solution to the original problem/post for others with similar issues.