PTC thermistors are self-regulating and protect the circuit behind them as well as themselves from overcurrent by automatically increasing their resistance value with rising temperatures. Furthermore, the PTC element does not need to be replaced after a tripping event because it resets itself when the cause of the failure is cleared and the temperature returns to a safe level.

Not only the component or temperature dependency of the PTC resistor must be taken into account, but also the voltage or frequency dependency, because these influence the maximum current value that can be applied to the application circuit. Please refer to 6.1 and 6.2 of PTC general technical information

An inrush current limiter PTC should be carefully selected according to the specified design target. First, the number of PTC elements required must be determined using the equation described in each data sheet. This includes the circuit design specifications as well as the PTC specifications of interest, such as reference temperature or heat capacitance. For consecutive charging/discharging cycles in a short period of time, a higher number of PTC elements might be required because heat dissipation may be limited within the time to the next cycle.