ROHM Semiconductor has recently announced the development of low-ohmic chip resistors optimized for current detection applications in compact equipment such as smartphones and wearable devices. The UCR006 series of ultra-compact (0.6×0.3 mm / 0.2 x0.1 inch) thick-film chip resistors is offered in resistances as low as 100mΩ, providing greater energy savings. They are also the first 0603-size(mm) / 0201-size(inch) resistors in the industry to ensure a temperature range of -55 to 155 degrees C in the low-ohmic region, and feature twice the rated power compared with previous products in the same size, enabling support for a wide range of applications. This higher power-handling capability in a smaller size makes them suited as replacements for larger 1005-size(mm) / 0402-size(inch) resistors, contributing to further miniaturization.
In order to operate smartphones and other electronic devices it is necessary to control the voltage and detect current internally, and resistances exceeding 100mÎ© are typically used. But to minimize power loss during current detection it is important to use the smallest resistance value possible while also providing sufficient power rating to ensure reliable performance.
To meet these needs ROHM has developed the UCR series of low-ohmic chip resistors designed for current detection. However, in recent years the proliferation of smart phones and emergence of wearable tech devices have increased the demand for components that are even more compact and consume less power. But in the case of resistors for current detection applications, a number of challenges must first be overcome in order to decrease chip size, such as maintaining low resistance values and tolerances while improving rated power.
ROHM's latest series utilizes new materials and a new structure to achieve class-leading low resistance (100mÎ©) in a 0603-size(mm), thick-film design. In addition, heat dissipation is improved, and rated power is increased to 0.1W twice that of conventional products. Operating temperature range has also been expanded in the low-ohmic region to an industry-best -55 to 155 degrees C, enabling compatibility with a greater variety of applications. These devices handle full-rated power up to 70 degrees C and derate linearly to 155 degrees C. And unique laser trimming technology makes it possible to achieve a resistance tolerance of ±1% (F Class), which has been traditionally difficult to realize at low resistances.
Furthermore, these new products have adopted the reverse-mount design utilized in the existing series in order to minimize resistance variations during soldering and ensure a temperature coefficient of resistance (TCR) between 0 and 300ppm/degree C, which reduces resistance fluctuations due to temperature changes. This provides high accuracy current detection required by today's high-performance devices. Going forward ROHM will continue to expand its lineup of compact, high accuracy resistors.