Trouble designing compensation network for TEC Controller using Analog ADN8831
This circuit requires an integration component of the PID controller.  The integration causes a ramp either up or down when the setpoint temperature is reached. The result is an oscillation around neutral when holding a constant temperature.  I missed this when testing because I didn't have a fan blowing on the TEC heat sink.  As a result, the heat sink got too hot and the TEC was unable to bring the temperature down: it never reached equilibrium, and I had assumed it was unstable.  Getting the right compensation here is important, otherwise the circuit burns significant power constantly heating and cooling the TEC.