New Industry Products

Varistors in the Spotlight: Advanced Circuit Protection Solutions

February 17, 2024 by Jake Hertz

TDK and Littelfuse have released varistor lines offering circuit protection in rugged and high-temperature environments.

Surge protection is a vital safety aspect of power system designs, and the varistor is a prominent component in most systems. 

A voltage-dependent resistor, varistors become effective short circuits when exposed to high voltages. Hence, they are ideal for redirecting large voltage spikes away from sensitive electronics and to GND (ground).

 

SM10 varistors.

SM10 varistors. Image used courtesy of Littelfuse

 

Recently, TDK and Littelfuse released varistor offerings with unique features fitting the needs of many applications. 

 

TDK SMD Varistors

TDK has added two families of surface mount device (SMD) varistors for handling applications with high surge current capability. 

 

SMD varistors.

SMD varistors. Image used courtesy of TDK

 

The first family is the B72210M* series, which offers a surge current capability of 6,000 A. This family is designed with horizontal and vertical variants, offering footprints of 22 x 15 x 11 mm and 15 x 10 x 20 mm, respectively.

The second family is the B72214M* series, rated for surge currents up to 10,000 A. Similarly, this series comes in horizontal and vertical variants, with footprints of 27 x 18 x 11 mm and 18 x 10 x 25.5 mm, respectively.

Notably, both device families come in SKUs varying from operating voltages of 1275 VRMS to 460 VRMS, roughly equivalent to 225 VDC to 615 VDC. Both series are also qualified to AEX-Q200 standards and have operating temperatures up to 125°C. The company claims both families are ideal for uses like on-board chargers, power supplies, and photovoltaic systems.

 

Littelfuse SM10 Varistors

Littelfuse’s suite of varistor offerings is dubbed the SM10 Series.

This notable series comprises the first surface-mounted metal oxide varistor (MOV) devices complying with the AEC-Q200 automotive standard, which is a testament to their robustness and reliability in harsh environments. A standout feature of the SM10 Series is its high operating temperature capability, withstanding temperatures up to 125°C. This ensures the varistors can reliably perform in extreme conditions, which is critical for automotive and industrial applications where high temperatures are common. 

 

The SM10’s repetitive surge capability. Image used courtesy of Littelfuse

 

The SM10 Series also boasts an ultra-high surge capability, which can handle up to 40 pulses of 6 KV/3 KA surges. With a wide voltage rating range from 130 VAC to 625 VAC, the SM10 Series’s versatility can meet the needs of most electronic applications. The compact design of these varistors, with a 15.7 mm x 8.5 mm x 14 mm footprint, also allows for efficient use of PCB surface space and facilitates automated Surface Mount Technology (SMT) PCB assembly processes, making them ideal for a wide range of electronic applications.

Littelfuse recommends these devices for power storage, onboard chargers, and general electrical products.