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DAC5670 termination

Daniel Pirkl
Prodigy 20 points

Figures 26 & 27 of the DAC5670 datasheet show the DAC output termination configurations with a 1:1 transformer and a 1:4 transformer.  Is a 1:2 transformer configuration also possible and why?

For the 1:1 transformer configuration, would the differential trace from the output termination to the transformer require a 50-ohm differential impedance to avoid signal distortion due to transmission line reflections?  Or how do you recommend handling this?

Thanks,

Danny

  • 0
    TI__Mastermind 20541 points
    Hi Daniel,

    Just so that we are on the same page, 4:1 ratio shown in Figure 27 is not the turn ratio but the impedance ratio . As you must know Zp/Zs = (Np/Ns)^2 so it is actually a 2:1 transformer.

    Please refer to this app note to get detailed information on how to implement passive termination for current output DACs.
    www.ti.com/.../slaa399.pdf

    Regards,
    Neeraj Gill
  • 0 in reply to Neeraj Gill
    Prodigy 20 points

    Thanks for the reply.

    We are on the same page. The presented impedance ratio's are 1:1: and 1:4.  My question is in regard to a 1:2 impedance ratio option not presented.

    Danny