Resistors and potentiometers

Looking over new resistor products for the past few months turned up some interesting completely new takes in this area, along with some updates and improvements of good old standard parts. Here are five products I thought might interest you.

The RK73H precision SMT thick-film chip resistor from KOA Speer is available in 0.5% and 1% tolerances, in a wide range of sizes from 01005 to 2512. The 2512 can handle 1 W — derating after 70ºC.  Values range from 10 Ω to 10 MΩ, and maximum working voltage runs from 15 to 200 V. The low-cost availability of 0.5% parts might make them your favorite way to go. The RK73H1ETTP1022D 10.2 K 0.5% part will cost you just 7 cents in 10,000 qty. But, a similar 1% tolerance is only 0.8 cents.

Fig. 1: The KOA Speer RK73H precision SMT thick-film chip resistor.

Vishay Intertechnology is sampling a new massive electro-pyrotechnic ignitor chip (MEPIC) resistor offering Joule effect or flash ignition for fast firing times down to 250 µs. The device is available in wraparound or flip chip versions, or can be integrated on a PCB substrate to simplify the assembly process. The 0805 MEPIC resistor is optimized for electronic ignitor applications in automotive safety systems for the deployment of airbags and other safety devices,  digital blasting in mining applications, and fireworks applications. 

Firing energy down to 1.5 mJ and ohmic value is 2 Ω (± 10%). The device provides very predictable, reproducible, and reliable behavior and has ESD withstanding to 25 kV without extra protection. The MEPIC resistor's performance meets no fire/all fire conditions and the requirements of USCAR, AKLV16, and major car manufacturer standards. The device is RoHS-compliant and ranges in price from $0.08 to $0.25 each.

Fig. 2: The MEPIC resistor is optimized for electronic ignitor applications.

Caddock's type USF270 ultra-precision, ultra-stable film resistor features 1,400 V maximum operating voltage. Values range from 990 KΩ to 5 MΩ and temperature coefficient is just 2 ppm/°C. Tolerance is 0.01% or 0.10%. The parts voltage coefficient is an excellent 0.02 ppm/volt and load life stability for 2,000 hours at +85°C and rated voltage is +0.015%, ±0.015%. Available similar models have voltage ratings of 300 or 2,500 V at +85°C.

Fig. 3: The type USF270 ultra-stable resistor from Caddock is rated for 1,400 V.

The FW Series of fusible wirewound axial-leaded resistors from Bourns provides both inrush current protection and fusible overcurrent protection. The series ranges from 1 to 7 W with resistance of 4.7 to 100 Ω. Models will fuse at 120 V or 240 V, and they are RoHS compliant.

Fig. 4: The TP Series resistors from Ohmite offer high power density.

The TP Series high-energy thick-film resistors from Ohmite Manufacturing are built on alumina substrate and  offer non-inductive performance and high power density. They also provide a high impulse energy capability of 100 J for a 100-ms pulse with a 100-μF capacitor, not to exceed 1,500 V. Double-sided screen printing of pulse-tolerant thick-film ink, coupled with a sophisticated laser-trimming process, maximizes the devices' energy-withstanding capabilities. The resistors come in 10-Ω to 1-MΩ values. The parts temperature coefficient is 100 ppm/°C for 1 to 100 Ω, and 50 ppm for higher values, and they are available with 1%, 5%, and 10% tolerances.