There are thermometer (temperature transducer or sensor) IC's and there are thermostat ICs. All of the sensor's I've seen have a positive output coefficient - voltage goes up when temperature goes up. Thermostat ICs do not make a linear output. The output is a digital logic low or high, and it changes state when the temperature crosses a threshold. The direction of the change varies with the chip, or some chips produce both.
Dozens on the market. Part number?????????????????????????????????????
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