Silicon linear thermistor takes on NTC temperature sensing

February 18, 2020 //By Nick Flaherty
TI's silicon linear thermistor technology enables devices costing as little at 5¢ with 50 percent higher accuracy than NTC thermistors
TI's silicon linear thermistor technology enables devices costing as little at 5¢ with 50 percent higher accuracy than NTC thermistors

Texas Instruments (TI) has developed silicon linear thermistor technology to take on negative temperature coefficient (NTC) thermistors with significantly higher accuracy for a similar price.

The 50 percent boost in accuracy enables operation closer to the thermal limits of the other components and the overall system, particularly at temperatures above 80°C.

Low cost NTC thermistors are widely used but struggle with degraded performance at temperature extremes and complex calibration requirements, which increases design time. The silicon linear thermistors have a similar price while minimising design time, reducing component count and increasing system performance in industrial, automotive and consumer applications where precise, real-time temperature readings are vital.

NTC thermistors provide less accurate temperature readings due to their low sensitivity and high resistance tolerance at temperature extremes. To compensate for these challenges, many engineers calibrate at three points across the temperature range or use multiple thermistors to monitor different temperature ranges. These approaches can still produce unreliable temperature readings, which can require systems to shut down before reaching their true thermal limit. The linearity and higher accuracy of TI’s thermistors enable single-point calibration, which maximises system performance and simplifies design.

The resistance of TI’s silicon-based linear PTC thermistor increases as the temperature rises, which decreases power consumption. And because they are made out of silicon, these devices have minimal self-heating compared to the materials of NTC thermistors.

The silicon linear thermistor also has a very low typical drift of 0.5% to improve the reliability of temperature measurements, enabling designers to boost system performance while maintaining safe operation.

Eliminating the need for additional linearisation circuitry or redundant NTC thermistors reduces the printed circuit board (PCB) layout size by a third compared to NTC thermistors. The thermistors are also one-tenth the size of other silicon-based linear thermistors, with a low profile and small package area that enable placement closer to thermal hot spots for faster thermal response and more consistent temperature measurements.

TI’s new thermistor portfolio with the TMP61


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