DS160PR421: DS160PR421 cascading

Gang Liu

Part Number: DS160PR421
Other Parts Discussed in Thread: DS160PR412, TMUXHS4412

Hello,

I have a question about the PCIE MUX, initially we planned to use the MUX for SSD hot swap, either go to RP1 or RP2.

Currently we are looking for a 3rd path, does TI have a similar product? Or can we use two layers of MUX cascading to reach one in three out?

Thanks.

over 2 years ago

0 Nasser Mohammadi over 2 years ago

TI__Guru* 93670 points

Greetings,

At TI we do not have 1:3 as you noted in your block diagram. Also, typically we do not recommend cascading muxes sine this makes tuning CTLE setting very complex and not reliable.

One possible solution is to use a DS160PR412 with a passive mux such as part shown below:

https://www.ti.com/lit/ds/symlink/tmuxhs4412.pdf?ts=1672336608722&ref_url=https%253A%252F%252Fwww.ti.com%252Fsitesearch%252Fen-us%252Fdocs%252Funiversalsearch.tsp%253FlangPref%253Den-US%2526searchTerm%253Dpassive%2Bmux%2526nr%253D1975

Regards,Nasser

0 Gang Liu over 2 years ago in reply to Nasser Mohammadi

Prodigy 130 points

Thanks for the reply, my understanding is as long as not cascading two redriver MUX as below then it should be OK, is that correct?

0 Nasser Mohammadi over 2 years ago in reply to Gang Liu

TI__Guru* 93670 points

Hi Gang,

The idea is to use TMUXHS4412 with signals from RP_A and RP_B - as you have shown in your block diagram. Then use PR12 with signals from TMUX and RP_C. This way PR412 - at the end of the transmission line - would do the final equalization.

We do have IBIS-AMI model for both TMUX and PR412 - you can use these along with your transmission line s-parameter model to do signal integrity analyses.

Regards,Nasser

0 Gang Liu over 2 years ago in reply to Nasser Mohammadi

Prodigy 130 points

Thanks Nasser,

I have marked TMUX and PR412 into the block, can you please help confirm is the same as you suggested? Thanks.

0 Nasser Mohammadi over 2 years ago in reply to Gang Liu

TI__Guru* 93670 points

Hi Gang,

Yes your understanding is correct.

Regards,Nasser

0 Gang Liu over 2 years ago in reply to Nasser Mohammadi

Prodigy 130 points

Thanks for the great help!

If I am use TUX and PR412 for some hot swap application, switching from A side to B side with power on, do you have any recommendations? Thanks.

0 Nasser Mohammadi over 2 years ago in reply to Gang Liu

TI__Guru* 93670 points

Hi Gnag,

We do not expect an issue.

Please make sure you connect PD pins of the PR412-421 to the PRSNT signal of the end point. Given this, RX detect would get restarted when the end point is plugged in.

Regards,Nasser

0 Gang Liu over 2 years ago in reply to Nasser Mohammadi

Prodigy 130 points

Yes, will do that. Usually there is a pull on on the PCB of the drive GND pin, when the drive is plugged in this pin will turn from high to low.

I am considering do I need to add some de-bouncing on this type of detection.

0 Nasser Mohammadi over 2 years ago in reply to Gang Liu

TI__Guru* 93670 points

Hi Gang,

Typically we have not seen a need for de-bouncing circuit on this signal and thus we don't see a need for this.

Regards,Nasser

+1 Gang Liu over 2 years ago in reply to Nasser Mohammadi

Prodigy 130 points

Hi Sasser,

Great, it sounds like this is a very common MUX application of this hard drive hot insertion.

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DS160PR421: DS160PR421 cascading