What is PTC?

POLY-FUSE devices are Polymeric Positive Temperature Coefficient (PPTC) devices which offer a resettable overcurrent protection alternative, thereby reducing warranty, service and repair costs. Ideal for situations where frequent overcurrent conditions occur or constant uptime is required, resettable PTCs (PPTCs) are typically used in consumer electronics, power line, telecom, I/O port, process control and medical equipment protection applications.

PTCs increase resistance as temperature increases due to increased flow. Designed to limit unsafe currents while allowing constant safe current levels, resistance will ‘resets’ automatically when the fault is removed and temperature returns to a safe levels.

Take one PCT for example, if your circuit tries to draw more than 250mA of current (if you have a bad short for instance) the PTC would ‘trip’ (by heating up). The increased resistance (trip state) would break the circuit and allow only a small leakage current.

The leakage current may still be enough to hurt some electronics but it’s much less than the 3A that the short may have allowed. Removing the short, the PTC ‘resets’ and allows current up to 250mA to flow again. It’s a resettable fuse that protects your system! Good for use on battery powered devices that need to protect again high-current accidental discharges.