Most semiconductors and the circuits comprised of them exhibit a positive temperature coefficient. NTC thermistors are well suited for compensating these responses to temperature changes. It is important to match the temperature of the compensating NTC thermistor to that of the component responsible for the temperature response.
RTI's SMD temperature measurement NTC sensors can operate over a wide temperature range (-55 to +150°C). They are stable throughout a long lifetime, and are small and comparatively inexpensive. Typically, they have negative temperature coefficients between -3.3 and -4.7%/°C at 25°C. RTI's SMD style thermistors are used in many applications that require a high degree of accuracy and reliability.
Some of the most popular applications of NTC thermistors include:
- Temperature Compensation
- Temperature Measurement & Control
- LCD Controls
- Power Transistor Stabilization
Selection Considerations for SMD NTC Devices
To determine the nominal resistance value of a thermistor at a specified temperature, multiply its RT/R25 value for the desired temperature and R-T curve from the table on NTC Resistance/Temperature Conversion Tables by its nominal resistance value at 25°C. As an example, the nominal resistance value at 80°C for a thermistor with the part number KR0805B103K is 10,000 times 0.157, the RT/R25 value in the R-T Curve "B" in the table under NTC Resistance/Temperature Conversion Tables.
Standard resistance tolerances at 25°C for RTI's SMD thermistors is ±10% and is indicated in its part number by the addition of the suffix K. To determine the resistance value at other than 25°C, add the appropriate DEV value from the NTC resistance/Temperature Conversion Tables to its resistance tolerance at 25°C. For example, the resistance tolerance at 80°C for a thermistor with part number KR0805B103K is ±10% ±3.0%, the DEV value from the R-T Curve "B" Table.
Although standard sizes, resistance values and tolerances are listed on SMD Standard Products and Sizes, custom sizes, resistance values and tolerances are available depending on the application and volume requirements.