ADA2200: Replacing RCLK signal with DAC output

Document created by brianharrington Employee on Jun 14, 2018
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Question from customer about the ADA2200 :

 

I need to excite my sensor with a sine wave. If I understand correctly, RCLK is only producing a squarewave, which is very unpleasant because it is quite tricky to filter out all the harmonics to obtain a pure sine wave.  The harmonics can induce a phase shift in my measurement. I want to avoid the complexity of designing and building an analog filter to remove the harmonics.

 

Can I use the DAC of my microcontroller to produce a sinewave and excite my sensor with that signal?

 

Answer:

Yes, you can generate a sinewave with a DAC and use that as an exitation signal instead of using RCLK.  It is important to phase-lock the sample clock of the DAC to the ADA2200 CLKIN signal.  In your case you could use the microcontroller to drive the CLKIN signal and control the DAC, which should make synchronization straightforward.  The input sampling rate of the ADA2200 is 64x the frequency of RCLK.  Selecting a DAC sample rate that matches the input sampling rate would result in very low harmonics with minimal anti-aliasing filtering on the DAC output.

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