Under & Over Temperature Sensor AC Switch for Heater, Fan, and Airflow Controller Using TMP01


Under & Over Temperature Sensor AC Switch for Heater, Fan, and Airflow Controller

The TMP01 is a temperature sensor that generates a voltage output proportional to absolute temperature and a control signal from one of two outputs when the device is either above or below a specific temperature range. Both the high/low temperature trip points and hysteresis (overshoot) band are determined by user-selected external resistors. For high volume production, these resistors are available on board.

The TMP01 consists of a band gap voltage reference combined with a pair of matched comparators. The reference provides both a constant 2.5 V output and a voltage proportional to absolute temperature (VPTAT) which has a precise temperature coefficient of 5 mV/K and is 1.49 V (nominal) at 25°C. The comparators compare VPTAT with the externally set tempera-ture trip points and generate an open-collector output signal when one of their respective thresholds has been exceeded.

Hysteresis is also programmed by the external resistor chain and is determined by the total current drawn out of the 2.5 V reference. This current is mirrored and used to generate a hysteresis offset voltage of the appropriate polarity after a comparator has been tripped. The comparators are connected in parallel, which guarantees that there is no hysteresis overlap and eliminates erratic transitions between adjacent trip zones.

The TMP01 utilizes proprietary thin-film resistors in conjunc-tion with production laser trimming to maintain a temperature accuracy of ±1°C (typical) over the rated temperature range, with excellent linearity. The open-collector outputs are capable of sinking 20 mA, enabling the TMP01 to drive control relays directly. Operating from a 5 V supply, quiescent current is only 500 μA (max).



  • Over/under temperature sensor and alarm
  • Board-level temperature sensing
  • Temperature controllers
  • Electronic thermostats
  • Thermal protection
  • HVAC systems
  • Industrial process control
  • Remote sensors





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