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SN75DPHY440SS: mipi signal integrity with long cable

miles lee
Prodigy 20 points
Part Number: SN75DPHY440SS

Hi,

my customer would like to know the mipi single quality with long cable?

the current application it might need a mipi re-timer IC. But I am not familiar with this kind chipset. How and when to use this mipi re-timer IC?

Example, if the overall trace length is as the following

Option 1:  198mm in total with 2 extra connectors.

Option 2:  148mm FPC calbe without extra connectors.

or timing can’t meet? how to know if we need use this to regenerate mipi signal or not?

I have checked section 8 of datasheet, but i still not very clear if we need this kind re-timer IC.

about the data rate, please base on Data Rate (200 Mbps to 1.5 Gbps) to provide the simulation or something. we can judge this easily.

thanks.

 

 

  • 0
    TI__Guru*** 146785 points

    Retimer is needed when your design failed mipi compliance test.

    RX of 440 can compensate 5db of trace loss at 750Mhz, TX of 440 can compensate 2.5db loss.

    we have s-parameter model for your simulation.

  • 0 in reply to Brian Zhou
    Prodigy 20 points

    we did the simulation, now we can know trace loss between CPU and LCD module is around 4dB(with two connectors will be 6dB).

    ======================

    Roughly estimated the loss = 0.4dB*10” + 1dB(connector) *2 ~ 6dB loss/ Total @ 1GHz

    Need to notice the connector of any impedance control.

    250MHz Signal need well impedance control to reduce the SI reflection.

    ======================

    Base on the current tract loss information, may I know whether this still need additional mipi retimer IC? Or what kind information is still lacking? 

    Please advise. thanks.

  • 0 in reply to miles lee
    TI__Guru**** 178126 points

    Does CPU or LCD module have any equalization function to compensate for the 6dB loss? If there is no equalization, or equalization is less than the 6dB insertion loss, then you would need to consider the use of re-timer IC.

    Thanks

    David

  • 0 in reply to David (ASIC) Liu
    TI__Guru*** 146785 points

    Lee:

        can you reply to David?