Resistors and potentiometers

There have been several interesting new resistor products of late — some with higher power in the same package. Impossible you say? Not really. Some new products also have much better surge capabilities. These improvements are coming from a combination of resistive element design and manufacturing methodology advancements. Engineers have to pay attention to the advantages of these new “standard” components.

The HCS Series shunt resistor from Stackpole uses a solid metal element that is elevated off the mounting plane. This increases the ability of the part to dissipate the heat into the ambient air and not into the PCB. The HCS2512, for example, will run typically 15° to 20°C cooler than an equivalent flat chip. The device features resistance values down to 0.3 mΩ and TCR of 50 to 150 ppm/°C. The series has 3- and 5-W ratings with 1% or 5% tolerance — and all this from just $0.30 to $0.70 each in full reel quantities.

 The HCS Series shunt resistor from Stackpole.

Also from Stackpole is the RNS Series of axial-leaded ultra-mini-metal film resistors with a ½-W power rating in a traditional ⅛-W package size.The RNS can achieve this high-power handling through tight manufacturing control of a unique power film alloy. It has flameproof silicone coating and is capable of precision down to 0.5% and TCRs as low as 25 ppm.

The RNS series resistor from Stackpole.
The Vishay Precision Group extended itsVTAZ series of bulk metal Z-Foil ultra-high-precision axial-lead resistor with a new version in the RBR57 MIL size. It is designed to provide a direct replacement, with better performance,for wire wound and metal film devices, and features an ultra-low TCR of ±0.05 ppm/°C nominal (0° to 60°C) and ±0.2 ppm/°C nominal (-55° to 125°C), and load-life stability of better than ±0.005% after 2,000 hours at rated power and 70°C. Tested to EEE-INST-002 guidelines for critical space applications, the VTA57Z offers 0.25-W power rating at +70°C and a 160-V maximum working voltage. It's available with in 5-Ω to 100-kΩ values and tolerance to ±0.01%.

Another important consideration in the choice of resistors for precision applications is where a significant signal voltage may change the resistance value. Under these conditions, bulk metal foil resistors behave better than other resistor technologies. Foil resistors also have a matched TCR for all values above 100 Ω and track over temperature better than wirewound devices. The VTAZ series has an inductance of

Also from Vishay we have the PHPseries  of precision thin film chip resistors that now include 0603 (375 mW), 0805 (625 mW), 1206 (1 W), and 2512 (2.5 W)case sizes. They feature 2x the power rating of traditional thin film chip resistors in the same case size. Available tolerance range from 0.1% to 5% with values from 10 Ω to 30.1 kΩ.

 Vishay's PHP chip resistors.

The resistors have a TCR of ±25 ppm/°C and a temperature range of -55° to 125°C. They  feature low noise of

The  CRF0805 SMT current-sense resistor from Bourns features a 0.5-W rating, derated from 70°C, in a small 0805 package. It has a resistance range from 5 to 20 mΩ.

Bourns offers you the CRF0805 SMT current-sense resistor.

This resistor has an operating temperature range of -55° to +170°C and a temperature coefficient of ±100 ppm/°C, with ±1% and ±5% tolerances are available. Price is from $0.15 ea/5,000 for a 1% version.

The TP810 thick-film high-energy resistor from Ohmite offers the benefits of non-inductive design and high power density. It provides the impulse energy capability normally associated with wirewound or composition resistors.

The Ohmite TP810 is surge tolerant resistor.  

The 1 x 1 x 0.24-in. 10-W device is the first of a new platform for the company's thick-film resistors. It is offered in eight standard resistance values from 10 Ω to 10 kΩ, with a 5% tolerance and suits surge protection applications. It has been successfully tested at 100 J over a 100-ms pulse.

A metal plate current sense resistor from KOA Speer.

The TLRH3AWTTE  metal plate chip current-sense resistor from KOA Speer features a resistance range of 10 mΩ to 270 mΩ with a 2-W power rating at 105°C, high corrosion protection, and a temperature range of -65° to 170°C. The 2512 package size resistor has a tolerance of 1%, low inductance, and a TCR of ±75 ppm in 10 to 22 mΩ, or ±50 ppm in 24 to 270 mΩ. The part is also AEC-Q200 qualified and costs from $0.60 ea/2,000.