Features and Benefits
- Simple Single-Wire Interface
- Measures Up to Four Thermistor Temperatures
- Low-Average Thermistor Current Minimizes Self-Heating Errors
- Internal Voltage Reference Isolates Thermistor from Power-Supply Noise
- Accommodates Any Thermistor Temperature Range
The MAX6691 four-channel thermistor temperature-to-pulse-width converter 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 four thermistors and an external fixed resistor (REXT) form a voltage-divider that is 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 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 the I/O pin low once again. The pulse corresponding to the 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. Between conversions, the MAX6691 falls into a 10µA (max) sleep mode, where the voltage reference is disabled and the supply current is at its minimum.
The MAX6691 is available in a 10-pin µMAX package and is specified from -55°C to +125°C temperature range.
- Home Appliances
- Medical Devices
Product Lifecycle Production
At least one model within this product family is in production and available for purchase. The product is appropriate for new designs but newer alternatives may exist.
Documentation & Resources
Thermal Management Handbook5/4/2010
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