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AD8436 DIP Package Output Unreliable

Question asked by AnalogLover on Mar 9, 2015
Latest reply on Feb 27, 2017 by jstaley

I am attempting to use the AD8436 DC coupled so that the Vout signal is the residual sum of squares (RSS) value of both the AC and DC voltages as seen on page 4 of the the application note here: http://www.analog.com/media/en/technical-documentation/application-notes/AN-1341.pdf

 

I have the AD8436 connected using a single supply (Vcc = 5.0 V Vee = GND) and have connected the chip exactly as Figure 5 (page 3) in the same application note listed above has said to. I am not using the sum pin and only connecting my input to the RMS pin. I am also using the DIP Package on a breadboard for testing purposes.

 

When I ground the input I get 0.237 V on the Out pin. One volt DC voltage applied to the RMS pin results in 0.24 V on the Out pin, and three volts DC results in 1.068 V on the Vout pin. It seems as though I have not configured the device correctly as I am not receiving the unaltered DC voltage on the output pin Vout. I am using a 10uF capacitor for CAVG, and a 0.1 uF for CCF. I have also tried using the SUM pin as the only input and tried using both the SUM and RMS pins tied together as the input, but with no better results.

 

Any help resolving this issue would be greatly appreciated.

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