Semiconductor e-News
June, 2006

Current monitor/PolySwitch combinations enhance overcurrent handling

In collaboration with Raychem Circuit Protection (a business unit of Tyco Electronics), Zetex has produced an application note, AN46 entitled: The use of Zetex current monitors with the PolySwitch™ overcurrent device.

Here is an introduction to the note:
Zetex current monitors work by measuring the small voltage across a low value sense resistor. This signal is translated to either a voltage or current output and then used in many applications to measure, control or protect the system. The sense device is normally a precision low ohm resistor. It is possible to make use of the small finite value resistance of a PolySwitch device from Raychem as the sense element.

PolySwitch devices are used where resettable overcurrent protection is required and can be used as a more practical solution than fuses. They are thermally operated devices with a finite trip time. The PolySwitch has a low ohmic resistance in its normal conduction condition that is ideal for use with a Zetex current monitor over a wide range of currents from hundreds of milli amps to tens of amps.

The note discusses the applications, considerations and limitations of using a PolySwitch device in conjunction with Zetex current monitor ICs to monitor current and give a pre-warning of an overcurrent trip event.

A link to this application note can be found at www.zetex.com/zxct, along with details of the full range of Zetex current monitors and associated datasheets.

For more about PolySwitch overcurrent devices, click here.

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