Littelfuse 777 Series Axial Lead Fuses

Littelfuse, Inc., the global leader in circuit protection, has introduced the compact 777 Series Fuse to provide protection for higher-wattage wall-mount chargers for battery-powered electronic equipment. Although chargers for earlier generations of mobile phones had relatively low wattage (typically about 5W), today’s highly compact chargers must often be able to handle 10-15W of power, which requires withstanding higher levels of current. The axial lead, 3.6mm x 9mm 777 Series Fuse incorporates an innovative type of filler material that provides a finely tuned balance between the surge tolerance necessary to prevent nuisance fuse tripping with the fuse’s ability to open safely when a short-circuit occurs. The 777 Series’ robust design lets it withstand up to 24 hits of 7.5kV ringwave surge; it will open safely on a direct short condition without producing soot, sparks, and sounds. Typical applications include wall-mount smartphone and tablet chargers and 10‑20W power supply modules for other battery-powered consumer electronics.

“From the consumer perspective, everybody wants their mobile electronic devices to recharge quickly, so they can get back to using them in the way they were intended. The 777 Series Fuse allows circuit designers to engineer fast, compact, and economical chargers that don’t compromise user safety,” said Daniel Wang, product manager for the 777 Series Fuse line. “Circuit designers can count on Littelfuse for robust fuse design and superior manufacturing quality.”


  • Its high interrupting rating design ensures the fuse will open safely under short-circuit conditions without producing soot, sparks, or popping noises.
  • The high surge withstand capability prevents nuisance tripping of the fuse caused by transient surges.
  • The fuse’s 3.6mm x 9mm footprint conserves board space, which makes it suitable for use in compact wall-mount charger designs.
  • Its epoxy coating provides insulation on the vertically mounted fuse body.