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Varistors from AVX specifically designed to protect USB data lines deliver under sub-nanosecond response time

31st January 2008

AVX

ES Admin

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AVX Corporation has developed the USB Series varistors specifically to protect the high speed data lines that make up the Universal Serial Bus (USB) against ESD transients. Key criteria that make the varistors ideally suited to protecting high speed serial data lines is their fast turn on times and very low capacitance. Response time is less than 1 ns, while a special design ensures the devices meet the rigorous testing criteria of the IEC 61000-4-2 15-kV (air) and 8-kV (contact) standards.

The zinc-oxide (ZnO) based, multilayer ceramic varistors feature non-linear, bi-directional voltage-current characteristics similar to back-to-back Zener diodes and an EMC (electromagnetic compatibility) capacitor in parallel. By effectively integrating this functionality into a single device they require significantly less PCB real-estate.

Available as 0603 and 0402 discretes or 0405 dual, 0508 triple and 0612 quad arrays, the varistors offer many electrical advantages over zener diodes in USB applications, including better repetitive strike capability, higher in rush current capability, faster turn-on-time, and inherent EMI attenuation.

Other features encompass a DC working voltage of less than 18 V, AC working voltage of under 14 V, transient energy rating (10 x 1000 μs) of 0.015 J, peak current rating (8 x 20 μs) of 4 A, typical capacitance of 10 pF or less, operating temperature of -55 to 125 degrees Celsius, plated tin over nickel terminations, and low clamping and operating voltages.

Typical applications are USB and Firewire data bus lines, I/O lines, 10/100/1000 Ethernet, video card data lines, laptops, PDAs and LCD monitors.