VPG Releases New Ultra-High-Precision Z-Foil Power Current Sensing Resistor With Low TCR to ±0.05ppm/°C, Tolerances to ±0.02%, ESD Immunity to at Least 25 kV, and High Power Rating of 2 W

The VCS232Z features a wide resistance range from 0.25 Ω to 500 Ω. Vishay Foil resistors are not restricted to standard values and specific as required values (e.g. 100.234 Ω vs. 100 Ω) can be supplied at no extra cost or delivery time. The resistor features a rise time of 1 ns, with effectively no ringing, thermal EMF of 0.05 μV/°C typical, a thermal stabilization time of <1 s (nominal value achieved within 10 ppm of steady-state value), current noise of 0.010 μVrms/V of applied voltage (<-40 dB), and a voltage coefficient of <0.1 ppm/V. Offering the utmost in ESD immunity, the device withstands electrostatic discharges up to at least 25 kV for increased reliability, and offers a non-inductive (<0.08 μH), non-capacitive design.

The power current sensing resistor released today is designed to improve performance by directly replacing wirewound resistors for pulse and current sensing applications in automatic test equipment, high-precision instrumentation, electron beam applications, power amplifiers, power supplies, and military and medical equipment. Today, designers of analog circuits are demanding discrete power current sensing resistors that approach the ideal in performance. They require stable, high-speed, high-accuracy components that will operate with assured, predictable reliability for years in a variety of environments. The Z-Foil resistor meets those demands with unequalled performance.

Four fundamental factors determine how ideal a precision power current sense resistor will be: initial resistance value; how precisely the value of individual resistors can be maintained; how precisely the end-of-life tolerance is maintained under a wide range of operating conditions and stress factors; and fast response time without ringing and fast thermal stabilization. Until the development of Foil resistors, precise control of all four factors was virtually impossible.

The VCS232Z resistor, containing the latest Z-Foil technology, achieves maximum stability, a near-zero temperature coefficient, and the ability to remove errors due to temperature gradients. This superior performance is built into every unit and does not rely on culling or other artificial means for uniform excellence. The stability of Vishay Foil resistors allows designers to eliminate other passive components and costly corrective circuitry. With the VCS232Z, only a minimal shift in resistance value will occur during its entire lifetime. Most of this shift takes place during the first few hundred hours of operation, and virtually no change is noted thereafter.

Current sensing is best achieved with a Kelvin connection, as featured with the VCS232Z, which removes the unwanted influences of lead resistance and lead sensitivity to temperature. Especially for low ohmic resistance values, a Kelvin connection reduces a measurement error due to the resistance of the lead wires and the solder joints as the sensing is performed inside the resistor, in or close to the active resistive bulk metal foil element.

The VCS232Z has a low thermal EMF, which is directly attributed to the special design of the device. Thermal EMF results from the thermocouple effect which exists between dissimilar metals. Under normal conditions, the voltage generated in one lead is cancelled by that of an equal and opposite polarity in the other lead. When a temperature differential exists between the two leads, a voltage difference will occur between them.

Offered with lead (Pb)-free or tin/lead alloy terminations, and compliant to RoHS Directive 2002/95/EC, samples and production quantities of the VCS232Z are available now, with lead times of five days for samples, and eight weeks for standard orders.