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Tyco resettable fuses provide primary protection

Posted: 24 May 2002 ?? ?Print Version ?Bookmark and Share

Keywords:lvr? tsm600 250? resettable fuse? telecom fuse? pptc?

Tyco Electronics' power components division has launched two products in its Raychem line. The company says its LVR series of PolySwitch resettable fuses is one of the first high-voltage devices suitable for line-side protection and its TSM600-250 is a minimum-parts solution for DSL/telecom equipment.

Used to guard against both overcurrent and overtemperature faults on the primary side of power supplies and transformers, the company's LVR series is rated for 240Vac applications, handles a maximum voltage of up to 265Vac and is available in hold currents from 50mA to 400mA.

"For many years, circuit designers have relied on polymeric positive-temperature coefficient [PPTC] devices for secondary-side protection," said Steve Zalewski, industrial-market manager for the power components division.

"This development makes possible, for the first time, resettable PPTC circuit protection on the primary side of power circuitry. Higher voltage ratings and the thermal characteristics of the LVR series make it a logical solution for power supply and charger designs," Zalewski said.

The LVR devices are available in straight-lead or kinked-lead configurations and can be supplied in tape-and-reel packaging for compatibility with high-volume assembly. Underwriters' Laboratories, Canadian Standards Association and T\V certifications are pending.

The second offering, the TSM600-250 PolySwitch, is intended to provide overcurrent protection for DSL and other telecom network equipment applications. The surface-mount device consists of two low-resistance PPTC components, matched to ensure balance between tip and ring for use in high-density multiport line cards and other telecom network equipment.

"By combining a single TSM600-250 device with our SiBar overvoltage devices, compliance with the lightning and ac power fault protection requirements of the Telcordia GR-1089 standard can be effected without additional components," said Rodrigo Rubiano, telecom and networking market manager.

"Compared to a typical SMT telecom fuse, the TSM600-250 reacts at higher speeds and helps provide protection even under low-current fault conditions. In addition, it assists in the coordination of primary and secondary overvoltage protection components and reduces energy let-through without compromising lightning surge capability of network equipment," Rubiano said.

The TSM600-250 occupies half the board space of two previous-generation 600V PPTC devices. It has a rated hold current of 250mA. The devices are packaged in tape-and-reel.

The LVR devices are priced at 20 cents to 34 cents each in OEM quantities. Pricing for the TSM600-250 starts at 80 cents each in volumes of 100,000. Lead time is eight weeks ARO.

Vincent Biancomano

EE Times

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