SUNNYVALE, CA-February 25, 2002-Maxim Integrated Products introduces the MAX6691 four-channel thermistor-to-digital converter. The MAX6691 measures the temperatures of four external thermistors and converts those temperatures to a series of output pulses whose widths are related to the thermistors’ temperatures.
An external fixed resistor is connected in series with each thermistor sequentially, forming a voltage-divider that is driven by the MAX6691’s internal voltage reference.
Because the voltage reference is active only during conversions, thermistor power dissipation is greatly reduced, slashing self-heating effects. This can improve measurement accuracy significantly, while reducing total system power. The internal voltage reference also gives greater immunity to system noise, further increasing measurement accuracy while simplifying system design.
The divider voltage is converted into a pulse that represents temperature. By measuring pulse widths, a microcontroller can read four temperatures over a single wire.
The internal voltage reference is shut down between measurements, reducing supply current to 3.5µA (typ). The MAX6691 operates between 3.0V and 5.5V over the military temperature range (-55°C to +125°C). It is available in a 10-pin µMAX package.
