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DAC8812 Input impedance

PAN-M
Mastermind 8375 points
Other Parts Discussed in Thread: DAC8812

Hi

The REFERENCE Input resistance is 4K to 6K ohm, written in the datasheet.
Is this a value between VrefX and AgndX?

PAN-M

  • 0
    TI__Genius 11750 points

    Howdy PAN-M,

    Your assumption is correct, but I thought I'd give you a little more background on the architecture of this DAC.  This DAC consists of a R-2R architecture, which is illustrated below.  IoutX typically connects to a transimpedance amplifier stage, and connects through virtual ground, which equates to the voltage of AGNDX (IOUTX (V)=AGNDX (V)).  The input resistance can then be seen as the equivalent resistance from VrefX and Agndx, which you may have noticed equates to R when simplifying the R-2R network.  The value of this 'R' is the input resistance specified in the datasheet, which has a typical value of 5K for DAC8812.

    Best Regards,

    Matt