TDK Corporation (TSE: 6762) presents two new series of ThermoFuse® varistors, which are equipped with monitor outputs and integrated thermal protective components for overvoltage protection.
The MT25 series (B72225M*) currently covers a voltage range from 150 VRMS to 385 VRMS, and its maximum surge current capability is 20 kA at a pulse form of 8/20 µs, according to IEC 61643-11. With dimensions of 25 x 28 x 14 mm, the completely encapsulated protective components feature a particularly compact design. Their monitor outputs are optionally available with or without electrical isolation.

TDK Corporation presents a new range of Open Mode chip varistors for electronic automotive assemblies that are directly connected to the battery. The new chip varistors offer reliable protection against transient surge voltages according to ISO 7637-2, and meet the failsafe requirements according to the VW standard VW 80808. Even when subject to excessive bending stress, short-circuits are avoided, which is particularly important for unswitched battery terminals (e.g. terminal 30).

Chip varistors and TVS diodes are commonly used as over-voltage protection components.
Their structural design and manufacturing methods are completely different, but they offer similar characteristics with regard to protection from static electricity.
They generally can therefore be used interchangeably in a circuit, but there are cases where chip varistors are considered to be not suitable.
For historical reasons, many of the specification items given in catalogs and data sheets are different, which makes it difficult to compare characteristics based solely on these data, unlike in the case of capacitors and other general components.
The aim of this article is to clarify the difference between varistors and diodes and to introduce data that can be used to compare the two.