VHigh-Precision Surface-Mount Current Sensing Chip Resistor

Vishay has introduced the new VCS1610 high-precision Bulk Metal Foil surface-mount current sensing chip resistor. The new device provides an absolute TCR of ± 2.0 ppm/°C from (55 °C to + 125 °C, + 25 °C ref., and tolerances to ± 0.5 %. While typical current sensing resistors offer a load-life stability of ≤ 0.2 % through a 1000-hour workload, the VCS1610 features an improved load-life stability of ± 0.02 % at + 70 °C for 2000 hours at rated power.

In addition to its low TCR, tight tolerance, and excellent load-life stability values, the VCS1610 offers a 0.25-W power rating at + 70 °C, and current noise of < - 42 dB. The resistor features a non-inductive (< 0.08 µH), non-capacitive design, and a 4-Kelvin terminal connection for increased accuracy.

The new device provides a broad resistance range of 0.1 Ω to 1 Ω. Like all Vishay Foil resistors, the VCS1610 is not restricted to standard values, and can be supplied with “as required” values (e.g. 0.2345 Ω vs. 0.2 Ω) at no extra cost or delivery time.

While other resistor technologies can take several seconds or even minutes to achieve a steady state thermal stabilization, the VCS1610 has an almost instantaneous thermal stabilization time of < 1 s (nominal value achieved within 10 ppm of steady state value), and a nearly immeasurable 1.0-ns rise time, effectively without ringing. The device is compliant to RoHS Directive 2002/95/EC, and is available with gold or lead (Pb)-free, or tin/lead terminations.

Featuring a new current resistor design that utilizes Vishay’s proprietary Bulk Metal Foil as the resistive element and ultra-fine photo-etching techniques, the VCS1610 eliminates the inter-parameter compromises inherent in all other types of precision resistors. Other technologies produce metallurgical changes in the resistance material, which noticeably change a device’s electrical characteristics. Such changes are not predictable, and thus randomly alter performance parameters. The construction of the VCS1610 results in an extremely low and reproducible reactance.

Traditional passive current sensors and shunts generate heat under power, which changes their resistance, and thus their voltage output. The VCS1610’s low absolute TCR eliminates errors due to temperature gradients, thus reducing a major source of uncertainty in current measurement. The VCS1610 can withstand unconventional environmental conditions, including the extremely high temperatures and radiation-rich environments of down-hole oil exploration and well logging, or the deep-sea underwater repeaters in cross-ocean communications.

Thermal EMF is another important factor in low-ohmic, current-sensing resistors used in DC circuits. The VCS1610 minimizes its effect through the use of appropriate materials between the resistive layer and terminations, resulting in a low thermal EMF of 0.1 µV/°C. Furthermore, electrostatic discharge (ESD) is known to produce catastrophic failures in thin film and thick film resistors at only 3,000 V. The Bulk Metal Foil resistor, however, withstands ESD events up to 25,000 V because its thicker resistance element and greater metallic mass afford much higher energy-handling capabilities than either the thin film resistor or the sparse, non-homogeneous metallic content of the thick film resistor.

In the past, designers had to compromise by utilizing other resistor technologies, such as thin or thick metal film, that had to start at very tight initial tolerances to assure that reasonable end-of-life tolerances are achieved. Because of its low power coefficient, low TCR, and very low thermal EMF, the VCS1610 can measure current changes very precisely, regardless of temperature variations. Designers can thus avoid overspecifying by relying on the VCS1610 resistor to deliver improved load-life stability and system performance.

The stability problems associated with analog circuits are very pervasive, but knowledgeable selection of a few high-quality resistors, networks, or trimming potentiometers in critical locations can greatly improve circuit performance, long-term application-related performance, as well as the designer’s peace of mind. Additionally, the overall system cost is often reduced when a knowledgeable designer concentrates costs in a few exceptionally stable components whose proven minimal-deviation load and environmental stability can often eliminate the necessity of additional compensating circuitry or temperature-controlling systems.

Samples and production quantities of the VCS1610 are available now, with lead times of five working days for samples, and five to eight weeks for standard orders.