AVX Multilayer Varistors Built to Respond to ESD Strikes in Less Than a NanosecondNovember 28, 2019 by Gary Elinoff
AVX’s TransGuard automotive VGAH series provides both EMI/RFI filtering and bidirectional overvoltage protection.
AVX’s glass-encapsulated multilayer varistors (MLVs) are designed for the harsh industrial and automotive arenas and for oil and gas applications.
MLVs based on zinc oxide (ZnO) exhibit bidirectional voltage-current (V-I) characteristics—akin to those of back-to-back Zener diodes—but with greater energy and current handling capabilities as well as sharper cutoff points.
In addition, the multilayer construction of the VGAH series provides significant inherent capacitance, which establishes EMI/RFI protection.
VGAH series of MLVs. Image from AVX
AVX’s automotive VGAH series of glass-encapsulated MLVs can combine bi-directional overvoltage protection and EMI/RFI filtering within one SMT component that can operate over a range of -55°C to +150°C.
Built for Harsh Environments
The series’ glass encapsulation provides protection against harsh environments and processes, which include challenges imposed by acids, salt, and chlorine flux.
Power derating curve (current, energy, power). Image from AVX
These devices are said to respond to an ESD strike in less than a nanosecond and exhibit multiple strike capabilities.
There is no derating of either current handling or energy absorption over the specified temperature range.
The members of this series are aimed at applications in harsh, high-temperature environments.
This may include applications that involve downhole drilling equipment, power tools, renewable energy systems, DC motors, turbochargers, and pencil coils. That might also be useful for vehicular relay applications.
AVX’s TransGuard automotive VGAH series of glass-encapsulated multilayer varistors. Image from AVX
Jiri Machanicek, product marketing manager for circuit protection at AVX, explains that “The new VGAH series of MLVs provide TVS protection in their on-state and broadband EMI/RFI filtering in their off-state, don’t require any current or energy derating over the entire range of rated operating temperatures, which spans -55°C to 150°C, and have a compact form factor that ruggedly withstands harsh-environment conditions and processes and satisfies increasingly common demands for lightweight, space-saving, multifunctional components.”
There are a total of 14 members of this series. Specifications across the series include:
- Working voltages: 16VDC to 31VDC and 11VAC to 25VAC
- Clamping voltages: 40V to 65V
- Energy rating: 0.6J to 13.0J
- Load dump energy: 1.5J to 50.0J
- Peak current: 100A to 1800A
- Capacitance: 700pF to 15,000pF
They are variously packaged in SMD sizes 1206, 1210, 1812, 2220, and 3220. The smallest size, 1206, is 3.2mm x 1.6mm x 1.7mm.
The largest size, 3220, measures 8.2mm x 5.0mm by 2.5mm.
Operating voltage derating. Image from AVX
The VGAH glass-encapsulated MLVs feature RoHS-compliant nickel-barrier-over-pure-tin (Ni/Sn) terminations.
The units are compliant with the ESD performance requirements as defined by the AEC-Q200, ISO 10605, and IEC 61000-4-2 standards.
Around the Industry
There are many participants in this competitive marketplace.
Littelfuse’s AUML series of varistors have working voltages ranging from 18VDC to 68VDC and clamping voltages ranging from 40V to 135V.
Load dump energies range from 1.5J to 50J. They are available in 1206, 1210, 1812, and 2220 packages.
The MLVA series from Bussman is multilayer surface-mounted varistors that are available in 0201, 0402, and 0603 packages.
Working voltages range from 4VRMS to 20VRMS and 5.5VDC to 26VDC. Clamping voltage can be specified over various values from 20V to 58V.