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TPD2E2U06-Q1: impedance drop in TDR analysis

Masaoki Koide
Intellectual 580 points
Part Number: TPD2E2U06-Q1
Other Parts Discussed in Thread: TPD1E05U06-Q1, TPD1E05U06

Dear Sir,

Our customer is using TPD2E2U06-Q1 with FPD Link III serializer and deserializer in their system. 

They analyzed impedance on their system by TDR and found the drop from 100 to 75~85 ohm at TPD2E2U06-Q1.

Does the device affect to impedance on the signal pass this much? Could you please advise how to reduce the drop?

If the device is not suitable for FPD Link III, please let me know which device is better and the reason why you choose it.

Regards,

Koide

  • 0
    TI__Genius 12410 points

    Koide,

    I apologize for the delay in response. Are they doing single ended or differential.

    Also here is the S-parameter model for the TPD2E2U06-Q1 the customer can use to do more simulations.

    https://e2e.ti.com/cfs-file/__key/communityserver-discussions-components-files/138/5657.TPD2E2U06Q1.s2p

    Regards,

    Cameron

  • 0 in reply to Cameron Phillips
    Intellectual 580 points

    Cameron-san,

    Thank you for the feedback. They are doing differential. They have already used the S-parameter model for the TPD2E2U06-Q1 provided from you in the different thread.

    If you have any suggestion or comment for reducing the impedance drop, please let us know. If possible, I would like to send you their layout and impedance curve personally.

    Your cooperation would be appreciated.

    Regards,

    Koide

  • 0 in reply to Masaoki Koide
    Intellectual 580 points

    Cameron-san,

    Could you please give us your feedback? Your cooperation would be highly appreciated.

    Regards,

    Koide

  • 0 in reply to Masaoki Koide
    TI__Genius 12410 points
    Koide-san,

    I understand what you are seeing and believe the device could effect the signal that much. The capacitance of the device is the biggest factor in this.
    I can recommend that you use TPD1E05U06-Q1 which has a typical cap of 0.4pF.

    Regards,
    Cameron
  • 0 in reply to Cameron Phillips
    Intellectual 580 points

    Cameron-san,

    Thank you for the feedback. We understand that the impedance depends on its capacitance, so you recommend the lower capacitance device, TPD1E05U06-Q1.

    I'll share this information with our customer. For the reference, do you have any other idea to reduce impedance except for changing device ?

    Regards,

    Koide

  • 0 in reply to Cameron Phillips
    Intellectual 580 points

    Cameron-san,

    We were asked about TPD1E05U06-Q1 from our customer as follows. Could you please advise about them? Your prompt reply would be highly appreciated.

    - Is TPD1E05U06-Q1 suitable for FPD Link III signal using SerDes DS90UB913A/914Q-Q1?

    - Which is better way  to confirm the transmission characteristics of FPD Link III, seeing eye-pattern opening or impedance measurement? Do you have any criteria for them to evaluate signal quality?

    - Do you have any data about impedance of TPD1E05U06-Q1?

      We need an impedance curve like following. It's from TI application note, SLVA793.

    Regards,

    Koide

  • 0 in reply to Masaoki Koide
    TI__Genius 12410 points

    Koide-san,

    Both the eye diagram and the impedance measurement are important for the spec so they both have to pass to work

    Here is the S-parameter model I have for the TPD1E05U06 that you can simulate a TDR measurement with using the FPD Link III rise time

    https://e2e.ti.com/cfs-file/__key/communityserver-discussions-components-files/138/TPD1E05U06.s2p

    Regards,

    Cameron

  • 0 in reply to Cameron Phillips
    Intellectual 580 points

    Cameron-san,

    Thank you for the feedback. Very helpful. May I confirm whether TPD1E05U06-Q1 is suitable for FPD Link III ?

    Regards,
    Koide