ANALOG DEVICES MAX6691MUB+

The MAX6691MUB+ is a four-channel thermistor temperature to pulse width converter in 10 pin µMAX package. It measures the temperatures of up to four thermistors and converts them to a series of output pulses whose widths are related to the thermistors temperatures. Each of the 4 thermistors & an external fixed resistor form a voltage-divider that is driven by the MAX6691’s internal voltage reference. VREF and voltage across REXT are measured and converted to a pulse. The MAX6691 has a single open-drain I/O pin that can be readily connected to a variety of microcontrollers. The microcontroller initiates a conversion by pulling the I/O pin low and releasing it. When conversion is done, the MAX6691 signals the end of conversion by pulling I/O pin low once again. The pulse corresponding to first thermistor is sent immediately after the release of the I/O pin. The on-chip power-management circuitry reduces the average thermistor current to minimize errors due to thermistor self-heating.