HD3SS3212: Trace impedance

Hi Zach,

Zach Kimble said:

1. What trace impedance should I use for USB3.0? 90 ohm or 100 ohm?

For USB3.0, we recommend 90Ohm differential, with +/- 15% variance. You can find our design guidelines for USB3.0 in this datasheet: https://www.ti.com/lit/an/slla414/slla414.pdf?ts=1733766272554&ref_url=https%253A%252F%252Fwww.ti.com%252Fproduct%252FHD3SS3212

Zach Kimble said:

2. The ON resistance for this device is specified as 8 ohms max. How does this affect signal integrity? Does this create a large impedance mismatch? Do I need to adjust the differential pair impedance to account for the ON resistance?

ROn will cause the signal integrity to decrease slightly, which over longer distances might have an adverse affect, however you do not need to change your impedance to better match it. It is better to check the signal after going through the mux, and seeing if maybe something like a redriver will be needed.

Please let me know if there are any other questions.

Thanks,

Ryan