The HY5640 is a subminiature temperature controller for thermoelectric coolers (TEC). This device is intended for "heat or cool" fixed temperature applications where front panel controls and digital readouts are not required. The HY5640 uses a thermistor bridge to precisely measure and regulate the temperature of a device affixed to a TEC. With proper heat sinking, the power stage of this device will deliver up to +/- 2 Amperes of current to a TEC. This controller was designed for single power suppply operation down to +5V. In addition, the device can be operated with dual supplies where VS can be as low as +3V and VDD as low as +5V.