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Help with AD8302

Hi, I need to measure phase and magnitude of a signal against a reference in my project. Reading the datasheet, It seems that AD8302 evaluation board might be used for this.

I have a couple of questions that I wonder if someone can help though:

1) Both the input signal and reference are DC coupled square wave. The input signal is voltage output from a photodetector, and the reference is a output signal from the FPGA. I am wondering if I will need any additional signal conditioning before feeding siginal to AD8302?

2) Reading through other posts, it seems AD8302 becomes less accurate when the phases of the two signal are close. Can someone explain what range is considered "close"? What's the error range in this case? What the error when the phases of the two signals are, say, 90 degree apart?

Thanks in advance!

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  • I would use the eval board as is, unless you get some erroneous results.

    It may take some experimentation.  Take C1, C4, C5, C6 to 100nF and put the same on C2 and C8.  If you are still getting erroneous results, then make the caps even bigger, say 1uF.  But I think you may be able to get away with the stock component values being that you are at 1MHz.

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  • I would use the eval board as is, unless you get some erroneous results.

    It may take some experimentation.  Take C1, C4, C5, C6 to 100nF and put the same on C2 and C8.  If you are still getting erroneous results, then make the caps even bigger, say 1uF.  But I think you may be able to get away with the stock component values being that you are at 1MHz.

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