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Ultra-High-Precision Z-Foil Surface-Mount Current Sensing Chip Resistor

Ultra-High-Precision Z-Foil Surface-Mount Current Sensing Chip Resistor

Vishay Precision Group, Inc.'s Foil Resistors brand (VFR) has released a new ultra-high-precision Z-Foil surface-mount current sensing chip resistor that is the industry's first such device to combine a high power rating of 1 W at +70°C and low TCR of ±0.2 ppm/°C typical from -55°C to +125°C, +25°C ref.

By dissipating up to 1 W in the 1625 package size, the VCS1625ZP allows designers to use a single device to measure larger currents than previously possible. For high-power applications, the device offers tight tolerances to ±0.2% (0.1% and 0.05% are available) and a four-terminal Kelvin configuration for increased accuracy.

The VCS1625ZP features a power coefficient (∆R due to self-heating) of 5 ppm at rated power, a thermal stabilization time of <1 ns (nominal value achieved within 10 ppm of steady state value), and a wide resistance range from 0.3 ohms to 10 ohms. Any resistance value within this range is available at any tolerance with no additional cost or lead time effect. The resistor offers a rise time of 1.0 ns with effectively no ringing, short time overload of <0.005% (50 ppm), 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 electrostatic discharge (ESD) immunity, the device withstands ESD to at least 25 kV, for increased reliability, and offers a non-inductive (<0.08 µH), non-capacitive design. The Bulk Metal® Foil technology of the VCS1625ZP provides a significant reduction of the resistive component's sensitivity to ambient temperature variation (TCR) and to the self-heating effect caused by changing loads. This allows designers to guarantee a high degree of stability and accuracy in fixed-resistor applications. In addition, the resistor's design results in a very low thermal EMF of 0.05 µV/°C typical, which is critical in precision applications. The VCS1625ZP's load-life stability of 0.015% at +70°C for 2000 hours at rated power is an order of magnitude better than typical current sensing resistors.

The device's improved stability makes it ideal for tightened-stability reference voltage and precision current sensing applications in forced-balance electronic scales, measurement instrumentation, bridge networks, motor controllers, and medical and test equipment. In addition, the resistor can be tested in accordance with EEE-INST-002 (MIL-PRF 55342) for military and space applications. The all-welded construction of the VCS1625ZP is composed of a Bulk Metal Foil resistive element with plated copper terminations. The flat terminations make intimate contact with the resistive layer along the entire side of the resistive element, thereby minimizing temperature variations. In addition to the low thermal EMF compatibility of the device's metals, the uniformity and thermal efficiency of the design minimize the temperature differential across the resistor, thereby assuring low thermal EMF generation at the terminations. This further reduces the thermal EMF voltage, or "battery effect," exhibited by most current sensing or voltage reference resistors. The VCS1625ZP is available with tin/lead or lead (Pb)-free gold or tin termination options, and with additional post-manufacturing operations (PMO) to extend the operating temperature from +150°C to well above +200°C. Samples and production quantities of the VCS1625ZP are available now, with lead times of five working days for samples and eight weeks for standard orders. Pricing for U.S. delivery starts at $4.05.

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