FAQ: Operating the AD8362 Evaluation Board at Low Frequencies

Document created by enash Employee on Sep 2, 2010Last modified by AndyR on Jan 31, 2012
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Q.

I am having some problems getting the AD8362 evaluation board to work low frequencies (e.g. around 1-10 MHz). Do I need to make some changes to the evaluation board for operation in this frequency range?

 

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A.

The input balun on the evaluation board (ETC1.6-4-2-3) is specified to work from 500 MHz to 2.5 GHz. So, I would suggest removing this and driving the device single-ended as described in page 19 of the Rev. D datasheet.  Make sure that you use two input coupling capacitors that set a low enough input high-pass corner frequency (assume that the input resistance at the device is 200 ohms).  Another alternative would be to try and find a low frequency  4-to-1 balun that will fit on the existing footprint on the eval board. One option is MABA-010012-ES4302 (Macom) which will work down to 30 MHz.

 

If you want to operate below approximately 2 MHz, you will also need to add a capacitor to the CHPF pin. This moves the corner frequency of the offset compensation loop down in frequency.

 

Operation at low frequencies and setting CHPF are discussed on pages 20 and 21 of the Rev D data sheet and in AN-691 (Operation of RF Detector Products at Low Frequency)

 

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