TUSB522P: Can be placed in daughter board?

Kailun Liu

Part Number: TUSB522P

Tool/software:

Hi Team,

In DS, it shows that TUSB522P is in mother board. Can it be placed in daughter board and host is in mother board? The distance between host and redriver will over 10000mil, there is a FFC line connect DB and MB.

Follow up question is that: how to evaluate the influence of line capacitance?

6 months ago

0 Vishesh Pithadiya 6 months ago

TI__Mastermind 40810 points

Hi Kailun,

It is possible to place the TUSB522p on a daughter card while the host is on the motherboard. The trace length of over 10000mil may be too long for the TUSb522p to compensate for.

To measure line capacitance you can use either a TDE or an LCR. The effect of line capacitance is a slower edge on data transitions. Its best to have line capacitance as low as possible.

0 Kailun Liu 6 months ago in reply to Vishesh Pithadiya

TI__Expert 3153 points

Hi Vish,

The trace length of over 10000mil may be too long for the TUSb522p to compensate for.

Just further check with you, in datasheet it describes max 20 inches. Does it has to be less than 10 inches?

0 Vishesh Pithadiya 6 months ago in reply to Kailun Liu

TI__Mastermind 40810 points

Hi Kailun,

Yes, this is true in the datasheet, but the datasheet is assuming a single trace without vias and a width of 3.4 mil. In the customers application there will be 10000 mil of trace + jitter and loss of the 2 FPC connectors, and the loss of the FPC cable.

A redriver can only account for insertion loss, but cannot cleanup jitter well. This is why I am more conservative with the max trace length in your application. The TUSB522p can work here, it will just be higher risk.

0 Kailun Liu 6 months ago in reply to Vishesh Pithadiya

TI__Expert 3153 points

Got it. Thanks.

If TUSB522P had risk about this application. Does TI have other cost effective alternative solution?

0 Vishesh Pithadiya 6 months ago in reply to Kailun Liu

TI__Mastermind 40810 points

Hi Kailun,

Unfortunately, we dont have any retimers in our portfolio, but this topology with a separate MB and daughtercard is more tailored to retimers than redrivers. Are you able to provide the loss of the cable? I can try to estimate the risk using the following calculator:

8156.RX & TX trace length budgeting - TI information - selective disclosure - revI.xlsx

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