ROHM's new shunt resistors support miniaturization in high-power applications

ROHM developed the GMR320 series of shunt resistors, featuring a rated power of 10W. The GMR320 series is the highest-rated, power product in ROHM high-power, low-ohmic GMR series lineup.

Recent years have seen an increased requirement in the automotive and industrial fields for lower-power consumption in higher-power applications. This, in turn, requires shunt resistors that support accurate, high-power current detection to achieve efficient operation. ROHM’s GMR and PSR series of shunt resistors provide extremely accurate current detection even at a high power, making them ideal for applications in the automotive, industrial, and consumer sectors.

The newly developed GMR320 series is offered in a resistance value range from 5mΩ to 100mΩ and a rated power of 10W. This makes them ideal for automotive engine ECUs, headlamps, motors, and power supplies for industrial equipment and home appliances. Unique structure and optimized materials allow the GMR320 series to reduce surface temperature rise by 23 percent over standard products, ensuring ruggedness against overcurrent loads even though it has the smallest size among 10W class resistors in the market .

In addition, a high-performance metal alloy for the resistive material provides a low temperature coefficient of resistance (TCR), which makes it reliable and highly accurate current detection possible even in the low-resistance values.

On the other hand, for the PSR series, which is widely used as high-power shunt resistors, the maximum rated power has been increased by up to 15W and the standard TCR value has been improved by applying the terminal temperature derating method. Ultra-low resistances value from 0.1 to 3.0mΩ can be offered. Also, a higher-rated power and highly accurate current detection is provided in a compact package, contributing to greater miniaturization in automotive and industrial applications same as GMR series.

Furthermore, from October 2021, thermal simulation models for shunt resistors will be available. This will make it possible to perform simulations before designing the actual products, even in high-power applications where thermal design is particularly difficult, reducing design man-hours considerably.

ROHM is committed to continuing to expand its resistor lineup (a founding product) from low to high power, providing various tools and other technical support to contribute to the evolution of vehicles and industrial equipment by great energy savings and miniaturization.

ROHM newly developed the GMR320 series of high-power, low-ohmic shunt resistors while extending the rated power of the ultra-low-ohmic PSR series to cover the power range up to 15W.

Furthermore, both series are qualified under the AEC-Q200 automotive reliability standard for passive components, ensuring a maximum operating temperature of 170° C that provides strong reliability even in vehicle environments where temperatures can be particularly severe, such as in the engine compartment.

GMR320 series advantages
1. High-heat dissipation structure reduces surface temperature
One issue when using shunt resistors at high power is suppressing the rise in surface temperature of product. GMR320 series improves heat dissipation by conducting a thorough review of materials and adopting a proprietary structure that significantly suppresses surface temperature rise.

For example, when a 5mΩ product is used at 7W, the surface temperature of standard products can reach as high as 154.3° C, while ROHM’s new products suppress temperature rise to just 117.8° C, a difference of 23 percent. Moreover, superior heat dissipation makes it possible to achieve the smallest size (7.1 x 4.2mm) in the 10W class while ensuring stable performance without a change in resistance value, even at overcurrent loads.

2. Excellent temperature coefficient of resistance
Generally, the lower the resistance the higher the temperature coefficient of resistance (TCR). However, GMR320 series uses a high-performance alloy for the resistive element that ensures a very low TCR of ±25ppm/° C or less, even in the low-resistance range.

This limits the resistance drift due to heating-up to about half that of standard products in the low-resistance range, enabling high accuracy current detection that improves application reliability.

PSR series advantages
ROHM’s PSR series of shunt resistors which feature excellent TCR even in the ultra-low-ohmic range has been well-received in the automotive and industrial equipment markets exposed to harsh temperature environments.

Until now ROHM used ambient temperature derating for its shunt resistors, but this time terminal temperature derating has been applied, making it possible to drastically improve the rated power. For example, for the PSR500 series, the rated power has been increased from the conventional 5W to 15W, enabling support for a wider range of applications.

Learn more here.