VPG – Ultra high-precision wrap-around chip resistors range extended down to 5ohmJul 10 2012 - Passives [More Passives Articles]
Vishay Precision Group (VPG) has announced that its Vishay Foil Resistors (VFR) group has enhanced its VSMP series of Bulk Metal Z-Foil ultra-high-precision wrap-around chip resistors with an extended resistance range down to 5ohm for sizes 0805 and larger.
The devices feature ultra-low TCR of ±0.05 ppm/C typical (0C to +60C) and ±0.2 ppm/C typical (-55C to +125C, +25C ref.), and load-life stability of ±0.005% at 70C for 2,000 hours at rated power and ±0.01% at 70C for 10,000 hours.
Available in seven chip sizes, from 0603 to 2512, the VSMP series offers high power ratings up to 750mW at +70C and an excellent power coefficient of ±5ppm at rated power. The devices feature a wide resistance range from 5ohm to 125kohm, with tight resistance tolerance to ±0.01%. Any resistance value within this range is available at any tolerance with no additional cost or lead time effect. Matched resistor sets are available on request.
The extremely low TCR of VSMP resistors over a wide temperature range makes them suitable for the high demands of cryogenic applications. In addition, the devices are ideal for use in many alternative energy and smart-grid applications, where analog circuitry operates under severe environmental, thermal, and mechanical conditions. Designing and manufacturing equipment for this environment involves extreme challenges that seemed insurmountable until a few years ago. These challenges have an impact on the design of analog circuits in alternative energy applications, and on the role and expectations of precision resistors, which must be ultra-stable, ultra-reliable devices with an extremely low total error budget.
Many designers use a resistor’s TCR as a shorthand index to the resistor’s relative level of precision. While it is generally true that a better TCR does correspond to higher precision, this degree of precision does not maintain the same TCR/precision proportion across all technologies. For Bulk Metal Foil resistors, the stress / strain balance throughout the temperature and power application ranges ensures that none exceeds the elastic limit (Hooke’s law) for any material used and that all performance criteria are repeatable and reliable.
“In recent months, all sorts of precision electronic components have been targeted by counterfeiters who dump very realistic looking but unreliable copies of precision electronics onto the market,” said Yuval Hernik, senior director of applications engineering for Vishay Foil Resistors. “This is causing confusion about the differences between actual and published specifications, and it contaminates storehouses and circuits with unreliable and under-performing parts. It is said that imitation is the sincerest form of flattery. However, counterfeiting is a crime, and the consequences of substituting fake Bulk Metal Foil resistors for real ones in analog circuits, systems, and programs can be very grave indeed. That’s why it is more important than ever to verify that the foil resistors you’re using are in fact the high-precision devices you believe them to be. The best way to counter these fraudulent scams is to buy only from VFR or its authorized distributors and catalogue houses.”
Many users of precision electronic equipment suffer needlessly from unexplained instabilities and drifts due to noise effects. They resign themselves to making constant adjustments and troubleshooting, but, in fact, these can be avoided. Bulk Metal Foil VSMP resistors owe their low excess noise and high linearity to the type of material of which they are made: a cold-rolled metal alloy foil with a thickness of several microns.
Featuring a non-inductive (<0.08μH), non-capacitive design, VSMP devices offer a rise time of 1ns with effectively no ringing, a thermal stabilization time of <1s (nominal value achieved within 10ppm of steady-state value), current noise of 0.010µVrms per volt of applied voltage (<-40dB), and voltage coefficient of <0.1ppm/V. VSMP series resistors are immune to extraordinary incidents such as radiation exposure and withstand ESD spikes to at least 25kV.
The VSMP resistors’ full wrap-around terminations ensure secure contact during the manufacturing process and also provide stability during multiple thermal cyclings. The devices are available with both lead (Pb)-free and tin/lead alloy terminal finishes. Samples and production quantities of the Z-Foil resistors are available now, says the company.More news from Vishay Precision Group