A PTC Device is a resettable overcurrent circuit protection device that is typically used in applications where sensitive components are at risk from overcurrent conditions. It was invented by Raychem in 1989. Littelfuse has been selling PTC Devices since 1996. In March 2015, Littelfuse acquired the Raychem PTC business from TE Connectivity.

The ability of a PTC Device to reset after exposure to an overcurrent condition is an attractive feature in circuits that are not easily accessible to a user or technician or where constant uptime is required. Typical applications include port protection on personal computers such as the USB, FireWire, keyboard, mouse and serial ports, computer peripherals such as hard drives, video cards and hubs, cell phones, battery packs, industrial controls, lighting ballasts and motor controls. A summary of typical PTC Device applications is as follows:

Telecom	Computer	Consumer Electronics	Batteries
UL 60950, TIA-968-A, GR-1089 Applications	CPU	Set Top Boxes	Li-Ion, NiMH, NiCd Cells
ITU-T Recommendations	USB	Loudspeaker	Battery Packs
Customer Premise Equipment	Parallel Data Bus	Smart Card Readers
Analog Line Cars	IEEE 802.3	Mobile Phones
T1/E1/J1 and HDSL	IEEE 1394	Linear AC/DC Adaptors
ISDN	I/O Ports	Portable Electric Input Ports
ADSL	PC Cards	Electromagnetic Loads, Motors
Cable Technology	SCSI Cards	Solenoid Protection
Telephone Systems	Video Port	Home Appliances
Fiber Optic Networks	LCD Monitors	Power Tools