High-density overcurrent protection for DSL

A novel small-footprint low-resistance surface-mount device provides tandem resettable overcurrent circuit protection for use in high-density multiport linecards and other telecomms network equipment.

A novel small-footprint low-resistance surface-mount device provides tandem resettable overcurrent circuit protection for use in high-density multiport linecards and other telecomms network equipment.

The Raychem TSM600-250 PolySwitch device incorporates two matched, low-resistance PPTC (polymeric positive temperature coefficient) components into a single device yielding balanced protection on tip-and-ring lines with minimal attenuation of data transmission.

"By combining a single TSM600-250 device with 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, Telecommunications and Networking Market Manager for Tyco Electronics Power Components.

"Compared to a typical SMT telecom fuse, the TSM600-250 device reacts at higher speeds and helps provide protection even under low-current fault conditions.

In addition, the TSM600-250 device assists in coordination of the primary and secondary overvoltage protection components and reduces energy let-through without compromising lightning surge capability of network equipment".

The TSM600-250 device occupies half of the board space of two previous generation 600V PPTC devices and eliminates the risk of unmatched tip-and-ring line protection.

In addition to interrupting AC power faults, the device is robust to Telcordia GR-1089 lightning and has a rated hold current of 250mA.

The devices are tape and reel packaged for compatibility with high-volume assembly.

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