### Ceramic PTC Thermistor Catalogue - Thinking Electronics Industrial

```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.
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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 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.
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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
```