The MR Series is a family of power-rated surface-mount current sensing resistors that combines multiple resistive alloy materials, two structural variants, and two package sizes to address a wide range of accuracy, inductance, and surge-handling requirements within the standard 2512 and 2818 chip footprints. The AEC-Q200 qualification across the full range makes the MR Series suitable for direct use in automotive designs without additional component-level qualification activity.
The Normal Type (MR2512*Z and MR2818*Z) prioritises low inductance, achieving no more than 5nH across the resistance range. This is significant in switching power conversion circuits, motor drives, and other applications where the current sensing resistor carries high-frequency switching currents: at elevated frequencies, a resistor with significant inductance introduces reactive impedance that distorts the current waveform seen by the sensing circuit, causing measurement error and potentially destabilising control loops. The MnCu element in the MR2512*Z delivers a TCR of no more than ±50ppm/°C across the 2mΩ to 20mΩ range, while the MR2818*Z uses MnCuSn, MnCu, and NiCrAl alloys across its 1mΩ to 50mΩ span to maintain TCR within ±75ppm/°C to ±250ppm/°C depending on resistance value.
The Anti-Surge Type (MR2512*G) uses a construction engineered to withstand short-duration overload events that would degrade or destroy a standard low-inductance element. Its resistance range extends from 1mΩ to 50mΩ, with MnCu used from 1mΩ to 4mΩ and FeCrAl from 5mΩ to 50mΩ, maintaining TCR within ±50ppm/°C to ±100ppm/°C. The anti-surge construction absorbs transient energy without the resistance shift or physical damage that arises in standard elements subjected to the same stress, making it the appropriate choice for circuits where motor start-up inrush, capacitor discharge, or load dump events will periodically subject the shunt to currents well above its steady-state rating.
Short-time overload is rated at five times rated power for five seconds for the MR2512 and four times rated power for five seconds for the MR2818, with resistance change not exceeding ±1.0%. Environmental qualifications follow JIS C5201-1, IEC-60115-1, JESD22, MIL-STD-202, and AEC-Q200-006 methods, covering 1000-hour high-temperature exposure at 170°C, 1000-cycle temperature cycling from −55°C to +155°C, 1000-hour biased humidity at 85°C and 85% RH, 1000-hour load life at rated power, solder heat resistance at 260°C, dielectric withstanding voltage at 500VAC, bending strength, core body strength, and terminal strength per AEC-Q200-006. Resistance values are laser-marked in a four-digit format using the letter ‘R’ to denote the decimal position in ohms.
