• State TI Thinks Resolved
  • Replies 2 replies
  • Answers 1 answer
  • Subscribers 33 subscribers
  • Views 28 views
  • Users 0 members are here
Support feedback
Options
Options
Related

TMDS181: create a complete 4:1 MUX HDMI re-timer circuit.

Henry Wang3
Genius 3685 points

Part Number: TMDS181
Other Parts Discussed in Thread: HD3SS215, , TMUXHS4612

Hi Sir,

My customer currently evaluating the hardware design and exploring alternative solutions for the ITE IT6635.

They would like to consult with you on a specific architecture: If they cascade three TI HD3SS215 chips to form a 4:1 HDMI MUX, and pair them with one TI TMDS181 HDMI re-timer to create a complete 4:1 MUX HDMI re-timer circuit.

TI HDMI v2.0 4-in to 1-out active mux.jpg

Could this proposed architecture fully replace the ITE IT6635 in our design?

ITE6635.jpg

 

I would appreciate it if you could share your insights on the feasibility of this workaround, particularly regarding signal integrity, EDID handling, PCB layout, and overall switching performance compared to a single-chip solution.

Thank you for your time and support. I look forward to hearing from you.

 

  • 0
    TI__Guru**** 188841 points

    Hi,

    I would point you to this app note, https://www.ti.com/lit/an/scda047/scda047.pdf, on the effect of cascading MUX and its impact on the signal integrity. As noted in the app note, a multiplexer with a bandwidth close to or equal to the working frequency won’t be a good fit for minimizing losses in the system. A good strategy is to select a multiplexer with 1.5x – 2x the Nyquist frequency (twice your operating frequency) for sine waves and 5x-7x the fundamental (operating) frequency for square waves. This helps maintain that more of the signal gets retained when passing through the mux. So If this is a HDMI2.0 6Gbps design, then HD3SS215 is not a good fit as its bandwidth is too close to the 6Gbps, you will need to use a higher BW MUX. 

    The EDID is outside of the MUX and the TMDS181 and will be passed between the HDMI source and sink. So MUX and TMDS181 does not impact the EDID. 

    In terms of the layout, you will have to factor in the insertion loss of the two MUX with the pre-channel loss. Also with the two MUX introducing additional intra-pair skew, you will want to minimize the trace intra-pair skew as much as possible. You can also see this high speed layout guide as a reference, https://www.ti.com/lit/an/spraar7j/spraar7j.pdf.    

    Thanks

    David

  • 0 in reply to David (ASIC) Liu
    Genius 3685 points

    Hi Sir,

    Thank you for your response.
    Due to bandwidth limitations, would it be feasible to replace the TMDS181(6Gbps) with the TMUXHS4612(20Gbps)?