Medium power multilayer chip varistors

A range of medium-power, multilayer chip varistors from AVX Corporation, is available for transient voltage suppression and ESD protection in telecommunications and automotive applications..

Designated the Telecom Series VC14 and Automotive VC13 Series, they feature an operational temperature range from -55 to +125°C. Series VC14 devices meet interference requirements of telecoms equipment with a 2000 V rated test pulse of 10 x 700 µs duration as specified by CCITT or IEC 61000-4-5. For example, a 60Vrms varistor can reduce the interference voltage at the equipment connected from 2kV to less than 200V. Automotive versions, VC13, feature high energy ratings of up to 25 Joules, and satisfy Load Dump and Jump Start test requirements.

Zinc-oxide (ZnO) based, these multilayer ceramic varistors feature non-linear, bi-directional voltage-current characteristics similar to those of back-to-back Zener diodes having an EMC (electromagnetic compatibility) capacitor in parallel. By effectively integrating them into a single device, the varistors require significantly less board real-estate and reduced component placement costs.

Varistors offer a number of electrical advantages over zener diodes, including multiple strike capability without degradation, higher inrush current capability, faster turn-on time, and inherent EMI/RFI attenuation. The varistor is also suitable for protecting devices from induced slow-speed transient voltages and currents, as well as ensuring negligible degradation in signal integrity.

VC14 Telecomms versions are available in an 1812-size package while their automotive equiavalent, VC13, embody case sizes of 1206, 1210, 1812 and 2220 according to the required performance characteristics. Both types incorporate palladium silver terminations. Detailed operational characteristives are given on the AVX web site.

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