Current-sense resistors optimise power use on PCBs

Produced using two different proprietary manufacturing technologies known as ISA-Plan and ISA-Weld, the current-sense resistors meet stringent criteria with regard to thermoelectric voltage, long-term stability and inductance that allow electronics designers to optimise power use on PCBs more efficiently than otherwise possible.

Isabellenhütte power resistors are widely used in automotive applications such as battery management in electric, hybrid and conventional vehicles, ABS (anti-lock braking systems), ASR (anti-slip regulation), cruise control, power steering, fuel injection and traction control systems.

They are also found in power supplies, as shunts for energy meters and IGBT (insulated-gate bipolar transistor) power modules, and in various industrial, telecommunications and consumer applications.

In ISA-Plan devices, highly precise resistor elements are etched onto a homogenous film of one of Isabellenhütte’s resistance alloys — either Manganin or Zeranin — which exhibit a very low temperature coefficient of resistance (TCR).

They are electrically insulated, mounted on a metal substrate with good thermal conductivity, and packaged as small SMDs. The resistor material is thermoelectrically well matched to copper, reducing thermoelectric voltage to virtually zero. Heat conduction into the substrate permits excellent pulse power ratings.

ISA-Plan resistors are available with resistance values from 1mΩ to 4.7Ω, tolerances of 0.5%, 1% or 5%, power ratings from 0.5W to 7W, and TCR down to 20ppm/°C.

ISA-Weld power resistors consist of an electron-beam-welded composite of copper and a resistance alloy: Manganin, Zeranin, Noventin, ISAOHM or Aluchrom. 

These materials are flexible enough to be adapted to a range of geometries and applications and offer uniform current density and heat distribution within the resistor. ISA-Weld resistors offer resistance values from 0.1mΩ to 6.8mΩ, tolerances of 1% or 5%, power ratings up to 15W, and TCR down to 20ppm/°C.

The Isabellenhütte portfolio of high-precision, low-ohmic current-sense resistors is shipping now from RS in the EMEA and Asia Pacific regions.