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DAC38RF80: output resistors at output of DAC38RF80

LALIT VERMA
Expert 1655 points
Part Number: DAC38RF80

Hi TI,

We are using DAC38RF80 in our design which is a single ended output DAC.

I have a query regarding the the resistors used on output of DAC38RF80 Eval Board.

What is the purpose of these resistors? Do they function as attenuator or have some other purpose also?

For DAC38RF80, output power level is 0 dBm @2.1Ghz and power level decreases as the output frequency increases.

We are not using any amplifier for increasing the power level of DAC output.

So my question is can we connect the output of DAC directly to SMA connector using AC coupling capacitor only and not using these resistors?

An early response will be highly appreciated.

Thanks,

Lalit

  • 0
    TI__Mastermind 18095 points

    Lalit:

    Short answer is yes, you can eliminate those resistors and connect directly to SMA connector or other device.

    The components are a place-holder for a pi-pad attenuator or for matching options or for a 3rd order filter.  As you have noticed, we typically don't use it for anything and the circuity is bypassed.

    Note, the 5600 pF caps and 0.3pF cap around the balun are needed; these values are recommended by balun manufacturer to maintain broadband impedance.

    --RJH

  • 0 in reply to RJ Hopper
    Expert 1655 points

    Hi RJH,

    Thanks for the quick reply.

    We are using DAC38RF80 which have integrated balun. I think this recommended 5600 pf capacitor value is for the baluns which are used with DACs which have differential output and external baluns need to be used for converting the signal into single ended.

    Is there any recommended output capacitor value for DAC38RF80 which has integrated balun?

    Thanks,

    Lalit

  • 0 in reply to LALIT VERMA
    TI__Mastermind 18095 points

    Lalit:

    Yes.  Good point.  I got my parts messed up.  No specific AC coupling cap value required.  Choose one best suited for your frequency of operation.

    --RJH