Electronic Design

Current-Sense Metal-Element Resistors Boast Tight TCRs

The ULR series of ROHS-compliant surface-mount metal-element resistors feature tight temperature coefficients of resistance (TCR) and low inductance values. They offer designers an economical current-sense device that maximizes thermal performance and minimizes power consumption. The resistors come in 1206, 2010, and 2512 package sizes and feature power ratings of 1, 1.5, 2, 2.5, and 3 W at 80°C. Resistances range from 0.5 mΩ to 10 mΩ, with standard tolerances of ±1% and ±5% and TCRs as low as ±50 ppm/°C, depending on power rating and resistance value. Operating temperature ranges from –55°C to 170°C. The company will also produce devices outside these specifications to meet customer requirements. The ULR resistors are available in two versions, both featuring plated terminations that, in contrast to comparable components with copper terminals, streamline production and eliminate TCR degradation. The black-coated resistors (1 and 2 W) employ a low-resistance alloy plate. The green-coated resistors (1, 1.5, 2, 2.5, and 3 W) feature a printed-circuit board “clearance gap” that maximizes thermal performance and keeps the resistor’s “hot spot” off the PC board. Typical pricing for the resistors is approximately $0.14 each in quantities of 100,000. Lead time is from stock to six weeks.

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