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TS3DV642: Differential impedance measurement by TDR for TS3DV642.

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Replies: 7

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Part Number: TS3DV642

My customer asked us about differential impedance measurement by TDR for TS3DV642.
As you can see, it is stable at around 104 Ω without TS3DV642, but it is around 117 Ω with TS3DV642.

Figure1.:Without TS3DV642

Figure2: With TS3DV642

There is a difference with or without TS3DV642.

Is this an effect of ON resistance?
The difference between presence and absence of TS3DV642 is 13 Ω.
He is concerned that since the ON resistance of the TS3DV642 is TYP 6.5 Ω, since it matches when doubling it at the signal sink and source, the ON resistance is raised as it is.

Please let me know the above question.
Also please let me know the solution to this symptom.

Best Regards,

Y.Hasebe

  • Hello Hasebe-san,

    Yes, this impedance change is caused by Ron of the TS3DV642.

    Regards,
    JMMN
  • In reply to JMMN:

    Hello JMMN-san,

    Thank you for your reply.

    My customer want to reduce the increased impedance.

    Please let me know how to reduce the impedance.

    Best Regards,

    Y.Hasebe

  • In reply to yoshiki hasebe:

    Hello Hasebe-san,

    There is no way to modify the Ron impedance, but the customer can adjust the PCB impedance which may provide more margin.

    Regards,
    JMMN
  • In reply to JMMN:

    Hello JMMN-san,

    Thank you for your reply.
    I explained your comment to my customer.
    He asked us about as additional below questions.
    Please let me know additional below questions.

    1.On the principle that ON resistance influences:
     I understood that the cause is in ON resistance.
     However, I do not know why the ON resistance is added by TDR measurement.
     So, please let me know the principle of adding ON resistance.

    2.On the case of reviewing PCB impedance after HDMI-SW (TS 3 DV 642):
     Please let me know the specific case of actually taking such measures on the matter of adjusting PCB impedance after HDMI-SW (TS3DV642).

    Best Regards,
    Y.Hasebe
  • In reply to yoshiki hasebe:

    Hello JMMN-san,

    Could you please help us about yesterday's above questions.

    Best Regards,

    Y.Hasebe

  • In reply to JMMN:

    Hi, JMMN,

    My customer has the same problem, how can they adjust the pcb layout. Thanks!

    Thank you and Best Regards!

    Nicole Han

    Analog FAE

    Texas Instruments - China, Beijing

  • In reply to Nicole Han:

    What is their current PCB impedance? Can they lower it to 95ohm? If they have s-parameter of the board, can they share with us so we can simulate it first?

    Thanks
    David

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