Surface-Mount Bulk Metal Z-Foil Resistors for AMS Applications

Several PMO options are available to Vishay customers to further enhance the already-high stability of the new SMD wraparound devices based on the VSMP configuration. These include processing to remove the 100 ppm knee in the load life curve, such that the load life curve becomes virtually flat from time zero, and temperature cycling and elevated temperature exposure to further improve stability. Further information can be requested from foil@vishay.com.

The new SMD resistors for AMS applications are the industry's first devices to provide high power ratings up to 750 mW at 70°C with long-term stability down to ±0.005%, low typical TCR of ±0.2 ppm/°C, Power Coefficient of Resistance (ΔR due to self heating) of ±5 ppm at rated power, and tight tolerance of ±0.02%.

Z-Foil improves stability by an order of magnitude compared to any other resistor technology, allowing designers to guarantee a high degree of accuracy in fixed resistor applications.

The stability problems associated with analog circuits are very pervasive, but knowledgeable selection of a few high-quality resistors, resistor networks, or trimming potentiometers in critical locations can greatly improve the efficiency of circuit design and long-term application-related performance.

With the new SMD resistors for AMS high reliability applications, any value from 10 Ω to 100 kΩ is available with a device that can retains its initial accuracy within several parts per million. This means that the instrument calibration cycle can be extended, or, in applications where no calibration cycle is possible (such as space applications), the designer can rely on anticipated shifts or specify further stabilization with well documented enhancements to ensure compliance with end-of-life design criteria.

Designers often pay more than they need to for tighter tolerances simply to accommodate the resistance shifts they know to be inherent in a given application. Using the new SMD series (0805-2512) allows the use of looser tolerances than would be necessary with other resistor technologies. For example, after 2,000 hours under full rated load at 70°C, the resistance shift experienced by this SMD series is just 0.005 % or more than an order of magnitude lower than the typical 1.0% experienced by other resistor technologies.

Additional features include a low thermal EMF of less than 0.1 µV/°C, voltage coefficient below 0.1 ppm/V, inductance lower than 0.08 µH, and response time faster than 1 ns effectively no ringing. The noise generated by these resistors is less than -40 dB, or essentially noise-free.

A robust conventional wrap-around termination and top coating ensures safe handling during the mounting process and provides stability during the multiple thermal cyclings the device will experience over its lifetime.

Available in waffle-pack and tape-and-reel packaging, samples and production quantities of the new wrap-around AMS resistors with post-manufacturing screening are available now. Lead time for production quantities is six to eight weeks and can be accelerated on request.