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By treez
#159489
Hello,

We are using the SAM3N00B microcontroller's DAC output to provide a voltage.

The DAC's output voltage goes to an RC filter which is 1K and 100p.
Page 720 of the SAM3N00B datasheet says that the max load capacitance for the DAC can be no more than 50pF.
Since our 100p is not directly connected to the DAC pin, but is after the 1K resistor, will we thus be allright using the 100p capacitor?

Also, page 720 of the SAM3N00B datasheet says that the minimum resistor load for the DAC output is 5K....does this mean that any resistor that shunts to ground from the DAC pin must be greater than 5K?

SAM3N00B DATASHEET:
http://www.atmel.com/Images/doc11011.pdf
User avatar
By viskr
#161437
Like many things, I'll assume that you have tried this and it either performs to your needs or not. Though you are exceeding specs.

The 50 pF load capacitance would normally be an issue for stability if you are driving it directly, but you are driving it with a 1K series resistor, which for that is probably OK.

But the 1K resistor may be too small, as the 5K limit has to do with the drive capability of the DAC output. This may be the limit to achieve the full frequency response of the DAC, and in your case with the filter in the 10s of KHz you probably don't care. The average drive of the DAC into your filter is probably OK.
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