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C6748: DDR_ZP, 75Ohm

Stefan_Haas
Mastermind 25252 points

Hello,

a C6748 customer asks for clarification on the DDR_ZP pin.

The datasheet shows that a 50Ohm resistor needs to be connected, but is that also correct in case the customer board works with 75Ohm impedance?

What resistor shall be used in this case?

Thanks in advance, Stefan

  • 0
    TI__Intellectual 1670 points

    As stated in the data sheet, a 50 ohm resistor (+/-2%) is always used, it does not change based on the board impedance.  This resistor is not used to match board impedance, but to set internal currents.  Adjustment of the buffer impedance (to match the board impedance) comes from internal register settings, not this resistor.

    Always use a 50 ohm resistor on this pin.  Set the registers according to the impedance.

    Good luck!