High heat dissipation structure improves reliability and space-saving in automotive and industrial applications
ROHM has announced the availability of GMR50 series shunt resistors that are capable of delivering industry-leading 4W rated power (at electrode temperature TK=90°C). It is ideal for current detection in motors and power supply circuits used in automotive systems and industrial equipment.
This new series combines a revised electrode structure with an optimised device design that improves heat dissipation to PCB where the resistor is mounted on. The result is a 39 per cent smaller mounting area over conventional 4W rated products.
In addition, this new series can sustain against overcurrent loads and deliver stable current detection accuracy even when unexpected loads exceed the applied rated power.
Shunt resistors are widely used in the automotive and industrial markets for current detection. In the automotive sector, increasing functionalities are resulting in a greater number of motors and ECUs, which in turn require high-density mounting for components like compact, power shunt resistors. However, the currently available mounting area for applications are limited.
To meet these needs, ROHM previously released the GMR100 series of power shunt resistors in the 6.4mm×3.2mm (2512 type package) size. Since then, these have been well received in the automotive and industrial equipment markets that demand strict temperature requirements.
The newly released GMR50 series has been developed to meet the demand for further miniaturised components and higher power than conventional products. In addition to expanding the lineup of shunt resistors, the company also focuses to strengthen its technical support such as thermal simulations by offering unique solutions together with power devices and op-amps to help automotive and industrial customers.
- Heat dissipation for achieving the industry’s highest-rated power along with improved durability under overcurrent loads
To increase the rated power while reducing size, it is necessary to ensure long-term reliability against self-heating. So, the heat dissipation can be improved by revising the electrode structure and optimising device design. For example, when using a 5mΩ product at 2W, a surface temperature rise can be reduced by 57 per cent as compared to conventional 5025 size resistors.
1) High rated power contributes to greater space savings
The GMR50 series delivers superior heat dissipation, guaranteeing the industry’s highest-rated power (4W) in the 5.0mm×2.5mm package size at a terminal temperature of TK=90°C (and 3W at TK=110°C).
Improving rated power makes it possible to use shunt resistors one size smaller in the 4W class, reducing mounting area by 39 and contributing to greater space savings.
2) Excellent durability enables stable current detection
Shunt resistors are used in current detection circuits, but stable current detection is required even when a large current flows through the resistor due to failure of the detection target or ground faults/short-circuit.
This latest series provides greater durability against overcurrent loads than conventional products, resulting in minimal resistance change even when overcurrent above the rating flows for stable current detection accuracy.
3) ROHM can provide unique solutions (as a comprehensive semiconductor manufacturer)
In addition to shunt resistors, ROHM can provide a broad portfolio ranging from ICs to power devices as well as advanced technical support such as thermal simulation.
For example, with the newly developed GMR50 series mounted on PCB, it is possible to simulate surface temperature rise in comparison with ROHM’s conventional products. The simulation result suggests that it is able to suppress temperature rise over circuits that use two conventional 5025 size resistors in parallel, even when mounting just one unit.
- Excellent temperature coefficient of resistance in the low resistance region
This new series utilizes a high-performance metal alloy as the resistive element to provide superior Temperature Coefficient of Resistance (TCR) even in the low resistance region. As an example, 0 to +25ppm/°C is ensured for 5mΩ resistance.
This enables high accuracy current detection that is less affected by changes in ambient temperature, contributing to improved application reliability.
The lineup has been expanded to include the 5.0mm×2.5mm (2010 type) package GMR50 series in addition to the existing 6.4mm×3.2mm (2512 type) package GMR100.