ROHM’s new low-profile 12W metal plate shunt resistor

Shunt resistors have been used in power modules for industrial equipment for some time. Similarly, in the automotive sector the number of thin double-sided cooled power modules adopted in the main inverters of xEVs – demanding to incorporate power device chips (IGBTs and SiC MOSFETs) and shunt resistors to decrease housing size – is rising.

Conventional metal plate shunt resistors reduce the cooling efficiency of power devices due to their relatively high profile. But decreasing height has proven difficult, as it is necessary to prototype and evaluate a variety of welding materials in different configurations. ROHM is able to take advantage of its strengths in manufacturing and design to create small-lot prototypes in a range of welding materials and patterns. This flexible development capability tailored to market needs makes it possible to develop the thinnest power shunt resistors on the market.

The PSR350 utilises ROHM’s vertically integrated production system together with material and process optimisation to achieve a thickness of just 0.03 inches (0.85mm), about half that of conventional products in the 12W class. The same technology is used to develop the smallest size (0.25x0.25inch/6.4x6.4mm) 15W-rated shunt resistor in the industry (PSR330). This decreases size by about 65% compared to conventional products in the same class, helping to reduce the mounting area in a wide range of high-power applications. At the same time, the PSR100 will be available in a 0.2mΩ model that extends the lower limit from the existing 0.3mΩ to enable the detection of even higher currents.

Going forward, ROHM will continue to contribute to the miniaturisation and energy saving of high-power applications by improving the performance of its broad family of metal plate shunt resistors.

PSR series

ROHM’s PSR series covering the high-power range is increasingly being adopted in automotive and industrial equipment applications. Traditionally, there has been a trade-off relationship between rated power and size in resistors, making it difficult to achieve both at the same time. However, ROHM’s vertically integrated production system allows for a quick development cycle through small-lot prototyping. Optimising material selection along with the manufacturing process achieves high-rated power in a compact size while also reducing the temperature coefficient of resistance compared to general products at the same rated power. This contributes to greater miniaturisation and improved reliability in a variety of applications.

Application examples

• These new products are suitable for high-current sensing in applications equipped with motors and/or Li-ion batteries.
• Automotive: Electronic Power Steering (EPS), Electric Compressors, Main Inverters, On Board Charger (OBC), DC-DC, Battery Management System (BMS)
• Industrial Equipment: Power Modules, Power Tools, PV Inverters, Server Power Supplies, Uninterruptible Power Supply (UPS), Base Station Power Supplies
• Consumer Devices: Home Appliances (e.g. Air Conditioners, Refrigerators, Vacuum Cleaners, Washing Machines)