Description

The MAX6691 four-channel thermistor temperature-to-pulse-width converter measures the temperatures of upto four thermistors and converts them to a series of outputpulses whose widths are related to the thermistors'temperatures. Each of the four thermistors and anexternal fixed resistor (REXT) form a voltage-divider thatis driven by the MAX6691's internal voltage reference(VREF). VREF and the voltage across REXT are measured and converted to a pulse.The MAX6691 has a single open-drain I/O pin that canbe readily connected to a variety of microcontrollers.The microcontroller initiates a conversion by pulling theI/O pin low and releasing it. When conversion is done,the MAX6691 signals the end of conversion by pullingthe I/O pin low once again. The pulse corresponding tothe first thermistor is sent immediately after the releaseof the I/O pin.The on-chip power-management circuitry reduces theaverage thermistor current to minimize errors due tothermistor self-heating. Between conversions, theMAX6691 falls into a 10µA (max) sleep mode, wherethe voltage reference is disabled and the supply currentis at its minimum.The MAX6691 is available in a 10-pin µMAX packageand is specified from -55°C to +125°C temperaturerange.ApplicationsHome AppliancesHVACMedical Devices