IRC Inc. (Corpus Christi, TX) has developed the LRF3W Series, a line of ultra-low resistance surface-mount resistors capable of handling up to 3W in an industry-standard 1225 chip. IRC claims that they are the industry's smallest 3W current-sense resistors, and reports that they are suitable for application in high-power/high-frequency designs, including battery state-of-charge circuits, power supplies and audio amplifier output short-overload sensing applications. Their size also makes them suitable for automated assembly equipment, as well as wave or reflow soldering materials.
The ceramic-based LRF3W Series features IRC's four-terminal Kelvin connection design, which is designed to achieve resistance values of 0.003 ohms to 0.100 ohms. The resistors also exhibit inductance ratings of less than 0.4nH at 1GHZ. The resistors are rated of 3W at 70 degrees C. These devices have tolerances to ±1 percent and a temperature coefficient of resistance of less than ±100ppm per degree C.
According to Steve Wade, director of sales and marketing at IRC, the LRF3W Series employs a reverse-geometry termination. “This makes wider terminations possible, which in turn reduces solder joint resistance and thus enables the resistor to carry higher current at a lower overall temperature."
Typical pricing for the LRF3W Series resistors is approximately $0.35 each in quantities of 10,000, with delivery times of stock to six weeks. Samples are available immediately.
