Shunt resistor power boost from new electrode design

February 18, 2020 //By Nick Flaherty
Rohm has developed a high heat dissipation structure to boost the reliability and space saving of a shunt resistor in automotive and industrial applications
Rohm has developed a high heat dissipation structure to boost the reliability and space saving of a shunt resistor in automotive and industrial applications

The GMR50 shunt resistor series supports 4W of rated power at an electrode temperature (T K) of 90°C in a compact 5.0mm×2.5mm (2010 type package) size.  It uses a high-performance metal alloy as the resistive element to provide a Temperature Coefficient of Resistance (TCR) of 0 to +25ppm/°C for a 5mΩ resistance.

This enables high accuracy current detection that is less affected by changes in ambient temperature, contributing to improved application reliability, and makes it suitable for current detection in motors and power supply circuits used in automotive systems and industrial equipment.

The re-designed electrode structure improves heat dissipation to PCB where the resistor is mounted on. The result is a 39 percent smaller mounting area compaed to previous 4W shunt resistor designs. This also allows the devices to handle overcurrent loads and deliver stable current detection accuracy even when unexpected loads exceeding the rated power are applied, contributing to improve reliability in system level. For example, when using a 5mΩ product at 2W, the surface temperature rise is reduced by over half of a conventional 5025 size resistor.

The shunt resistor is a key part of a motor in automotive and industrial markets. In the automotive sector in particular where there are more motors and control units there is increasing pressure on the mounting area. Shunt resistors are used in current detection circuits, but stable current detection is required even when large current flows through the resistor due to failure of the detection target or ground faults/short-circuits. As a result, high density mounting is increasing, spurring demand for components including a compact power shunt resistor.

This shunt resistor family follows the GMR100 series launched in 2017 in a 6.4mm×3.2mm (2512) package, which has since been well received in the automotive and industrial equipment markets demanding strict temperature requirements. Rohm says it will continue to strengthen its technical support such as thermal simulations for automotive and industrial customers using the GMR50 where it is possible to simulate surface temperature rise


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