CN0359: Float of signal from Instrumentation Amplifier

We have set up EVAL-CN0359 and have the following problem. 
We are measuring the voltage from J5 pins 2 or 3.
These feed AD8253.
We see the expected distorted square wave on the scope but it is floating up and down between the rails.
Page 18 of the datasheet for AD8253 possibly implies that the inputs are not stabilized by a bias current path to ground in the CN0359 layout.
See also fig. 6 of your article by Kitchin concerning "Common Problems When Designing Amplifier Circuits".

Any advice here? T
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    •  Analog Employees 
    on Apr 24, 2019 6:07 PM over 1 year ago in reply to Brandon

    Hi all,

    Just wanted to leave a note saying Fritz has also sent me a probe to do some testing at our Wilmington site. 

  • +1
    •  Analog Employees 
    on Apr 30, 2019 1:31 PM over 1 year ago in reply to LBrodeur

    Hi Fritz,

    We have some preliminary testing done with a TOPAC probe that we have available here and we have seen no anomalies on the output signal. We have tested it with varying resistor values in place of the probe and was also able to get correct values with the readings and the output signal looks as expected concluding that the circuit works as expected with the given test cases.

    We have received the probes yesterday and have been able to start the testing of the board with your probe. We are able to see and replicate your test case where the output of the in-amp swings to the negative rail.

    We are now trying to explore the possible instances why this would happen. Lia and our team are sharing our data to gain better traction in solving this issue.

    Please stay tuned on the advancements of our testing.

    Thank you,