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DAC8822: Full Scale Range calculations and resistor tolerances

Evan Lewis
Prodigy 10 points
Part Number: DAC8822


Tool/software:

Hi! When trying to determine the full scale range of DAC8822 I noticed that the datasheet states "The R-2R ladder presents a code-independent load impedance to the external reference of 5kΩ ± 25%". Does this mean that the full scale output of my DAC could have as much of a variance of ± 25% from chip to chip? Assuming a reference voltage of 5V, that would mean we could have an output anywhere from ± 0.8mA - ± 1.3mA? The datasheet also states that Rfb can be between 8k-12k (tolerance of ± 20%). How consistent from chip to chip are these variances and is there anything I can do to ensure I am getting a consistent full scale range on the output? Thanks!

  • 0
    TI__Mastermind 42273 points

    Hi Evan,

    While the total impedance of the ladder seen by the reference can vary by 25%, the ladder is well matched to itself. So code to code changes and the full scale error will not be 25% in terms of output voltage at the TIA. We share accuracy and full scale error specs in the datasheet.

    Rfb is also well matched to the equivalent resistance of the ladder, so the 25% tolerance if this resistance does not have an effect on the output of the DAC output voltage at the TIA. If you were to use an external Rfb then the 25% ladder tolerance would have more of an effect.

    Best,

    Katlynne Jones