Ultra-High-Precision Z-Foil Molded Surface-Mount Resistors

The devices provide a low typical TCR of ±0.05 ppm/°C from 0°C to +60°C, +25°C Ref, and ±0.2 ppm/°C from −55°C to +125°C, +25°C Ref., an excellent PCR (ΔR due to self heating) of ±5 ppm at rated power, tolerances to ±0.01%, load-life stability of 0.005% (50 ppm) at rated power for 2000 hours at ±70°C, and end-of-life tolerance to less than 0.1%. This superior performance is built into every unit, and does not rely on culling or other artificial means for uniform excellence.

The SMRxDZ series is based on a new resistor concept developed by Vishay that utilizes a proprietary Bulk Metal Foil and new fine photo-etching techniques created by the Company, so that the conductor can be considered a flat wire. Because the metals used are not drawn, wound, or mistreated in any way during the manufacturing process, the SMRxDZ series maintains all its design, physical, and electrical characteristics. These factors are both measurable and predictable before, during, and after manufacturing.

The SMR1DZ and SMR3DZ offer a variety of screening options in accordance with MIL-PRF-55182. The enhanced resistors feature flexible terminations to ensure minimal stress transference from the PCB due to a difference in thermal coefficient of expansion (CTE). The devices offer a wide resistance range of 5 Ω to 80 kΩ, and like all Vishay Foil resistors, are not restricted to standard values. Vishay can supply as required values (e.g., 7 kΩ vs. 7.5678 kΩ) at no extra cost or delivery time.

With Vishay Bulk Metal Foil resistors, 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. The SMR1DZ features a power rating of 250 mW at +70°C, while the SMR3DZ offers a power rating of 600 mW at +70°C. Both devices have a load-life stability of ±0.005% for 2000 hours at 70°C; a low voltage coefficient of < 0.1 ppm/V; current noise less than -40 dB; and low thermal EMF of 0.1 µv/°C. They offer a fast rise time of 1.0 ns, effectively without ringing, and feature a non-inductive (<0.08 µH), non-hot-spot design.

The level of the voltage produced in electronic discharge (ESD) and static electricity depends on a number of factors, such as the affinity of the two bodies and the air humidity, and can reach over 25 kV. The SMR1DZ and SMR3DZ resistors offer the utmost in ESD immunity, withstanding electrostatic discharges up to 25 kV, for increased reliability.

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 and long-term applications-related performance, as well as the designer's peace-of-mind. Additionally, 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. The SMRxDZ series with Z-Foil technology offer a good example of this principle.