TUSB8041: SSTX/SSRX connection and AC coupling capacitors location in specific USB topology

Matan Hershkovitz

Part Number: TUSB8041

Hi,

I have the following topology.

1. Can you confirm that SSTX/SSRX connection between ICs and connectors, numbered from 1 to 5, are OK?

2. I recall that AC coupling capacitors should be placed near the connectors - for both upstream and downstream (numbered 1 and 5). Is that correct?

I've marked the location of the coupling capacitors by PINK oval.

However, I'm not sure where to place the coupling capacitors in other connections, numbered from 1 to 5. Can you please tell where those should be placed?

What about placing also on SSRX lanes? I know there was an ECN which defines this as an option.

Thanks!

over 1 year ago

0 Brian Zhou over 1 year ago

TI__Guru*** 146785 points

For 1 and 5, 100nf cap is needed on TX, 330nf or none cap on RX.

for 2: need 100nf on both TX and RX .

for 3 and 4, need 100nf on both TX and RX either on 3 or 4, but just one one side of mux.

Regards'

Brian

0 Matan Hershkovitz over 1 year ago in reply to Brian Zhou

Intellectual 905 points

Hi Brian,

Thanks for your answer.

For 1 and 5 - where the RX capacitors should be placed?

For 3 or 4 - the capacitors should be placed closer to the mux or the hub?

Can you please explain the reasoning for all items?

Thanks,

Matan

0 Brian Zhou over 1 year ago in reply to Matan Hershkovitz

TI__Guru*** 146785 points

Metan:

for 1 and 5, RX cap should be placed close to connector.

for 3 and 4 , cap should be placed on TX of hub side, so one on 3 Tx and one on 4 TX side

signal is from TX to RX, so cap is close to TX to minimizes both the spread of DC content and the turnaround time of reflections.

Regards

Brian

0 Matan Hershkovitz over 1 year ago in reply to Brian Zhou

Intellectual 905 points

Thanks, Brian

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TUSB8041: SSTX/SSRX connection and AC coupling capacitors location in specific USB topology