ADT14

The ADT14 is a temperature sensor and controller that generates an output voltage proportional to temperature and provides four temperature trip points. The four trip points, or temperature setpoints, and their hysteresis are determined by voltage levels set by the user. An on-chip voltage reference provides an easy method for setting the temperature trip points.

The ADT14 consists of a bandgap voltage reference combined with four matched comparators. The reference provides both a temperature-stable 2.5 V output, and a voltage proportional to absolute temperature (VPTAT) which has a precise temperature coefficient of 5 mV/K = 5 mV/(°C +273.15). The VPTAT output is nominally 1.49 V at +25°C. The comparators determine whether the VPTAT output is above the voltages set up by external resistive dividers (temperature trip points) and generate an open-collector output signal when one of their respective thresholds has been exceeded.

Hysteresis is programmed by a user-selected voltage at the hysteresis pin. This voltage adjusts the hysteresis current which is used to generate a hysteresis offset voltage. The comparator's noninverting inputs are connected in parallel, which guarantees that there is no hysteresis overlap and eliminates erratic transitions between adjacent trip zones.

Using a proprietary thin-film resistor process in conjunction with production laser trimming, a temperature accuracy of ±3°C at 25°C is guaranteed. The open-collector outputs are capable of sinking 5 mA, and provide TTL/CMOS logic compatibility with an external pull-up resistor. Operating from a single 5 V supply, the quiescent current is 600 mA max.