Ceramic PTC Thermistor: Glossary Zero-power resistance (RT) The zero-power resistance is the resistance value measured under specified temperature conditions, and the self-heating during measurement can be negligible. Resistance-temperature characteristic (R-T curve, see Fig. 4) R-T curve is relationship of zero-power resistance and temperature of CPTC thermistor at specified direct voltage. It is a curve drawn on a semi-logarithmic coordinate graph (Temperature (T) is on X-axis and resistance (R) is on Y axis). Fig.4 R-T Curve Log R Rmax R25: Zero power resistance at 25℃ Rmin: Minimum resistance TRmin: Temperature corresponding to minimum resistance Tc: Curie temperature or switch temperature RTc: Switch resistance (RTc=2xRmin) Rmax: Maximum resistance TRmax: Temperature corresponding to maximum resistance RTc=2xRmin R25 Rmin T(℃) 25℃ TRmin Tc TRmax Minimum resistance (Rmin) Minimum resistance is the lowest resistance on R-T curve and corresponds to TRmin, temperature of minimum resistance. (see Fig. 4) Temperature of minimum resistance (TRmin) TRmin is temperature that corresponds to Rmin on R-T curve. Curie temperature or switch temperature (Tc ) Cuire temperature is temperature that corresponds to RTc =2 ×Rmin. When the temperature is reached, a step-like increase of CPTC thermistor resistance is started. THINKING ELECTRONIC INDUSTRIAL CO., LTD. All specifications are subject to change without notice. 3 www.thinking.com.tw 2014.05 Ceramic PTC Thermistor: Glossary Voltage-current characteristic (V- I curve, see Fig. 5) V-I curve is relationship of applied AC or DC voltage at thermistor terminations and steady-state current when thermal equilibrium is reached in still air at 25℃. Fig. 5 V-I Curve I. Imin. V Vmax. Rated voltage (VR) Rated voltage typically equals to voltage of supply source. Maximum operating voltage (Vmax) Maximum operating voltage is maximum AC or DC voltage that continuously applies to thermistor and does not exceed maximum overload current. Maximum link voltage (VLmax) Maximum link voltage is maximum DC voltage of filter capacitor in inrush current limiting application. Withstanding Voltage (VW) Maximum voltage that CPTC thermistor can withstand under specific conditions. Maximum operating current (Imax) Maximum operating current is maximum permissible current before reaching curie temperature. Tripping current (IT) Tripping current is the lowest current that causes thermistor to trip to high resistance at specified temperature (preferably 25℃). Maximum non-tripping current (IN) Maximum non-tripping current is maximum current that thermistor keeps definitely in its low resistance condition at a specified ambient temperature (preferably 25℃). THINKING ELECTRONIC INDUSTRIAL CO., LTD. All specifications are subject to change without notice. 4 www.thinking.com.tw 2014.05 Ceramic PTC Thermistor: Glossary Heat capacity(Cth) Heat capacity is energy (in J) for increasing 1K of thermistor’s body temperature. Power consumption (P) Power is measured with rated voltage and Imax after CPTC thermistor trips. Operating time(to) Operating time is the time for current of CPTC thermistor to change to 0.5 times of Iin after tripping is occurred. Recovery time(tr) Recovery time is the time which the resistance value of PTC recovers to 2 times of R25. Responding time(ta) Responding time is the time that A current takes to reduce to B current after CPTC thermistor trips. (A and B currents are specified in specifications.) Surface temperature (Tsf) Surface temperature is temperature of CPTC thermistor’s surface when the component is operated at specified voltage and ambient environment is in a state of thermal equilibrium for a certain period of time. Typical ambient temperature is 25℃. Sensing temperature (Ts) Sensing temperature is temperature related to a defined resistance value in the steep region of R-T curve. THINKING ELECTRONIC INDUSTRIAL CO., LTD. All specifications are subject to change without notice. 5 www.thinking.com.tw 2014.05