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DAC7578 Output impedance

Takumi Suzuki1
Mastermind 8420 points
Other Parts Discussed in Thread: DAC7578

Hi,

I would like to ask you about the output impedance of DAC7578.

There describes on the datasheet page 4 as below.

You know, the impedance is 4.5ohm(TYP) and its measurement condition is "At midscale input".

I do not understand "At midscale input" well.

My understanding is that 4.5ohm is measured at 1/2 reference voltage output. (= If AVDD is 5V, that is 2.5V.)

Is my idea correct?

Best Regards,

  • 0
    TI__Mastermind 46290 points

    Suzuki-san,

    Your understanding is correct.

    This is the measurement practice because the biasing of the transistors in the output stage is different when the output is near the positive or negative supply rails and therefore creates a sort of "anomalous" representation of the output impedance.

    Generally speaking our electrical characteristics table will specify output impedance at "nominal" mid-scale biasing conditions and the typical characteristics curves shown later in the datasheet show more information about operation near the supply rails.

  • 0 in reply to Kevin Duke
    Mastermind 8420 points

    Kevin-san,

    Thank you very much for your reply!

    I understood well.

    Best Regards,