New current sense resistors roll out with performance improvements

By Jean-Jacques DeLisle, contributing writer

Developers at Bourns Inc. have developed a new family of sense resistors, the CSM2F series, which uses a metal alloy element that has been electron-beam-welded to tin-copper terminals. This design is said to offer excellent electrical properties, additional mechanical strength, and ease of solderability. An added benefit of the metal-alloy current sense resistors is that it allows for a minimal thermal electromagnetic field (EMF) as low as 0.25 µV/K.

The CSM2F sense resistors are designed for use in high-current applications while still providing very low resistance. The devices deliver resistance values as low as 50 µΩ, continuous current of up to 1,000 A, and power ratings of up to 50 W. Engineered for design flexibility, the series features three different footprint sizes: 8518, 7036, and 6918 metric.

The high-current sense resistors also provide a low temperature coefficient of resistance (TCR) of 50 ppm/°C at temperatures between 20°C to 60°C. This extremely low TCR allows these sense resistors to maintain a desirably low drift of resistance with temperature.

Three different models comprise the new CSM2F series of resistors, all of which feature metal-alloy construction and are RoHS- and AEC-Q200-compliant. These model series include the CSM2F-8518 Series, CSM2F-7036 Series, and the CSM2F-6918 Series.

Thanks to high measurement accuracy and “relatively” low cost compared to other technologies, said Bourns, the current sense resistors are finding homes in most market segments, particularly battery management systems in automotive, industrial, and computer electronics.

Other companies also have been developing new current sense resistors. Stackpole Electronics Inc. recently launched the HCSM2818 5-W surface-mount current sense resistor. This new component features an all-metal element as well as a molded construction in resistance values of 4, 5, 10, 15, and 20 mΩ. Along with an array of resistance values, tolerances of 1% or 5% are available. The device offers a TCR of 200 ppm for resistors below 10 mΩ and 75 ppm for values of 10 mΩ and higher.

The new current sense resistors provide full-power operation up to 100°C and have an operating temperature limit of 170°C, making them suited for high-power current sensing that experiences significant self-healing, said the company. This series also features large terminals that allow for a thermally efficient connection, which helps reduce convection and conduction cooling, making them suited for high-voltage applications.

The HCSM2818 series is RoHS-compliant and halogen- and lead-free. The resistor series is priced at $0.38 each in full-reel quantities. The parts are available direct or through Stackpole’s franchised distributors.