Devices Available With Screening in Accordance to MIL-PRF 55342 and MIL-PRF 49465 for High-Precision Applications
MALVERN, Pa. - March 10, 2010 -Vishay Intertechnology, Inc. (NYSE: VSH) today announced that it has enhanced the CSMseries of ultra-precision, surface-mount, current-sensing resistors in the compact 2512 and 3637 case sizes. The improved devices offer a standard TCR of ± 15 ppm/°C max. (- 55 °C to + 125 °C, + 25 °C ref.), with ± 10 ppm/°C max. available on request, and an extended resistance range down to 1 mΩ.
The CSMfeatures a low thermal electromotive force (EMF) that is critical in many precision applications. The device's all-welded construction is composed of a Bulk Metal® resistive element with welded copper terminations, plated for soldering. The terminations make true ohmic contact with the resistive layer along the entire side of the resistive element, thereby minimizing temperature variations. The resistor element is designed to uniformly dissipate power, thereby minimizing parasitic contact resistance and contact resistance variation for a low thermal EMF of 3 μV/°C.
Traditional passive current sensors and shunts generate heat under power, which changes their resistance, and thus their voltage output. The CSM's low absolute TCR reduces errors due to temperature gradients, thus reducing a major source of uncertainty in current measurement. The CSMcan 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.
Featuring a four-terminal (Kelvin) design, load-life stability to ± 0.2 % at 70 °C for 2000 h at rated power (typical current sensing resistors offer a load-life stability of ≥ 0.5 % through a 1000-hour workload), and available with screening in accordance to EEE-INST002 (MIL-PRF 55342 and MIL-PRF 49465), the devices provide high stability and performance in precision current-sensing applications.
Designers often unnecessarily pay for tighter tolerances than required simply to accommodate the resistance stability shifts they know to be imminent in an application due to the large application-related changes in the components they selected. Selection of a high-stability component like the CSMin these applications eliminates the need for shift allowance due to "planned instability," and allows the use of looser initial tolerances than would be necessary with current-sensing resistors based on other technologies.
The CSM2512features a 1-W power rating over its entire resistance range from 1 mΩ to 200 mΩ, while the CSM3637is rated for 3 W from 1 mΩ to 10 mΩ and for 2 W from 10 mΩ up to 200 mΩ. Vishay Foil resistors are not restricted to standard resistance values, and can be supplied with "as required" values (e.g. 2.3456 mΩ vs. 2 mΩ) at no extra cost or delivery time.
The devices feature a maximum current up to 54 A, low inductance of < 5 nH, and thermal EMF of 3 μV/°C. The CSM2512and CSM3637 offer compact dimensions of just 0.25 in. by 0.125 in. [6.35 mm by 3.175 mm] and 0.360 in. by 0.370 in. [9.14 mm by 9.4 mm], respectively, with a height profile of 0.025 in. [0.635 mm].
Available in waffle-pack or tape-and-reel packaging, the CSM2512and CSM3637are available with lead (Pb)-free and tin/lead alloy terminations. The devices with lead (Pb)-free terminations are compliant to RoHS directive 2002/95/EC.
Samples and production quantities of the enhanced resistors are available now, with lead times of five days for samples, and five weeks for standard orders.