Spotlight on Passives

Apr 1, 2008 12:00 PM

High-Power Resistors

From IMS, the N-Series of high-power resistors and terminations on AlN offers unmatched power handling and flexibility in meeting specific circuit requirements.

The N-Series is available in cases 0505 to 3725, thicknesses 0.015 in., 0.025 in. or 0.040 in., and multiple termination styles, including single wrap to groundpad, center stripe, extended wrap or single sided with backplane for added power dissipation.

Standard resistance range is 10 Ω to 2 kΩ with tolerances to 2%. N-Series resistors and terminations are available with RoHS-compliant platinum silver, pre-tinned platinum silver or wire-bondable gold terminals, making them ideal for any application operating above 10 W.
IMS
Portsmouth, R.I.
www.ims-resistors.com

Charging Resistors

From Epcos, the J20X series of charging resistors employ a PTC ceramic construction that enables them to be self-protecting despite their small size. The family consists of three products — the J201, J202 and J204 products — whose specifications are listed in the table. These resistors overcome a key limitation of ohmic resistors that are typically used to limit current when charging capacitors. Those resistors can fail if the capacitor short circuits or a relay malfunctions when short circuiting the capacitor. These faults can subject ohmic resistors to fatally high power levels.

In contrast, when the J20X series of resistors is subjected to a fault, the temperature and inherent resistance of the PTC ceramic increases in line with the increased ohmic losses and limits the current to a safe level. Typical applications include industrial power supplies, frequency converters and UPS systems in the power range from 500 W to 50 kW. In such applications, a link-circuit capacitor is used to smooth the generated dc voltage or as an energy-storage device in the link circuit. Unit pricing is approximately $2.35 each in quantities up to 5000.
Epcos
Munich, Germany
www.epcos.com

Precision Surface-Mount Resistors

TT electronics IRC's PPC Series combines the precision of a thin-film resistor with the power-handling capabilitiess of a thick-film resistor. The component merges the high-surge capability (up to 1500 W for 1 ms) of IRC's CHP Series with tolerances to 0.1% at TCRs of 25 ppm/°C.

Available in 1206, 2010, 2512 and 3610 package sizes, the cylindrical surface-mount PPC Series resistor features maximum power ratings of ⅛ W, ½ W, 1 W and 2 W, with working voltages of 200 V, 300 V, 350 V and 500 V, respectively. Resistance ranges from 100 Ω to 10 kΩ, with tolerances down to ±0.1% and TCRs of ±25 ppm/°C.

Pricing for the PPC Series surface mount precision power resistor starts at $0.35 each in quantities of 2500. Lead time is from stock to 8 weeks.
TT electronics IRC
Corpus Christi, Texas
www.irctt.com

Military SMPS Stacked Capacitors

KEMET's military-grade ceramic stacked capacitors are intended for high-reliability switch-mode power supply and pulse-energy applications. The SMPS Stacked Capacitors are qualified to Military Performance Specification MIL-PRF-49470 and DSCC Drawing 87106. Their low ESR and ESL make them ideally suited for input and output filtering of power-supply applications as well as snubber applications.

The capacitors are available in case codes 3, 4 and 5 (larger case codes 1, 2 and 6 will be available in the third quarter of this year), X7R dielectric, and voltage ratings from 50 Vdc up to 500 Vdc, and capacitance values up to 47 µF. The chip stack is horizontal and the leadframe attachment is a high-temperature solder. They are also available in unencapsulated (unpotted bare chips) or encapsulated (potted assembly) styles.

With an operating temperature range between -55°C and 125°C, and with capacitance shift limited to ±15% over that range, the SMPS Stacked Capacitors are an excellent choice for electrical applications, general-purpose applications and high-frequency power-supply circuits.
KEMET
Greenville, S.C.
www.kemet.com

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