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.