When using the DAC interpolation mode on the ADuC7060/61, what are the recommended RC values for the external filter?
For the evaluation work at ADI for the DAC interpolation mode, the following values for the external RC filter were used:
R=1K and C=100nF
Some further information:
The reason the external filter is required in interpolation is because, the DAC output switches between 2 x output values at the rate selected by the interpolation clock – the filter is required to average this.
If you look at the raw DAC output before the filter, you will see a slight saw-tooth like level on the DAC output. These two levels are the result of adding 4 x extra bits to the normal 12-bit DAC output. The min. value is with these 4 extra bits low, the max value is with these 4-bits high.
From our evaluation of the DAC in interpolation mode, the DAC is monotonic to 14-bits.
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