Hello, I am a little bit confused when analyzing this design.
In fact, after following the path of the sensor output signal (TEMP PWM), I see that it was conditioned (impedance matching by U20B;amplification by U20A) than transmitted, after another amplification, to the feedback pin of the IC. But the signal temp in transmitted to the micro-controller (in another sheet) is simply the "image" of the sensor output, not a signal obtained from a real current measurement. Is that technique widely used in temperature control with Peltier elements?

 

Certainly the circuit is quite confusing and rather "circular". A guess is that the "off" state resistance, or voltage, is used to sense the temperature. Note the area with all the 1% resistors.

 

Certainly the circuit is quite confusing and rather "circular". A guess is that the "off" state resistance, or voltage, is used to sense the temperature. Note the area with all the 1% resistors.

Thank you; so are they thermistors?