Spotlight on Magnetics

Feb 1, 2007 12:00 PM

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This “Spotlight on Magnetics” section looks at recently and soon-to-be introduced inductors and transformers for power-system applications. Although many of these components target specific applications, a common thread among them is the quest for small size, particularly low package height. In addition, most of the devices profiled here offer RoHS compliance and tape-and-reel packaging.

The component descriptions provided are summaries of the standard specifications, features and options offered by the vendors. However, many of these suppliers are willing to customize their products further to meet user requirements.

Low-Profile Shielded Inductors

Stackpole Electronics announces three series of shielded power inductors that offer high performance in combination with a low package height and a small footprint. The devices target dc-dc converters, notebook computers and LCD screens, among other applications.

The PSDB series features inductance values ranging from 1.3 µH to 1000 µH, current ratings up to 10 A and three package heights ranging from 3 mm to 5 mm. The SFM series offers inductance values from 1 µH to 680 µH, current ratings up to 7.7 A and six sizes with heights as low as 1.8 mm. The PDRH series provides inductance values from 1 µH to 100 µH, ratings up to 1.5 A, a footprint less than 4 mm per side and a height of just 1.8 mm.

In the PSDB and PDRH series, an electrode is connected directly to the ferrite core. Typical unit pricing is $0.34 for the PSDB series, $0.28 for the SFM series and $0.26 for the PDRH series.
Stackpole Electronics
Raleigh, N.C.
www.seielect.com

Inductors for Voltage Regulators

From TT electronics' BI Technologies Magnetic Components Division comes a series of high-power molded surface-mount inductors targeting nonisolated voltage-regulator designs. Members of the HM72A series are low-profile, RoHS-compliant inductors with a pressed-powdered iron-alloy core construction that optimizes current saturation levels while minimizing ac and dc losses.

The devices feature inductance values from 100 nH to 33 µH, saturation levels up to 80 A and an operating temperature range of -40°C to 155°C. The HM72A inductors are available in three package sizes: 7.23 mm × 6.8 mm, with a height of 3 mm; 11.5 mm × 10.5 mm, with height options of 2.5 mm and 4 mm; and 13.5 mm × 13 mm, with height options of 3.5 mm, 5 mm and 6.5 mm. Typical pricing is approximately $0.55 to $0.85 each.
BI Technologies
Fullerton, Calif.
www.bitechnologies.com.

High-Frequency, High-Current Inductors

Four low-profile, high-current inductors from Vishay Intertechnology feature maximum operating frequencies up to 5 MHz and inductance values down to 0.047 µH. According to the vendor, the IHLP series inductors offer the lowest DCR/µH for their respective package sizes, making them suitable for VRMs and other dc-to-dc converters.

The IHLP-1616AB-11 and IHLP-1616BZ-11 inductors offer a maximum frequency of 1 MHz, while the IHLP-1616AB-01 and IHLP-1616BZ-01 feature a maximum frequency of 5 MHz. Inductance ranges from 0.047 µH to 4.7 µH. All four devices feature dimensions of 0.160 in. × 0.175 in., and occupy the 1616 footprint. The IHLP-1616AB-01 and IHLP-1616AB-11 inductors offer profiles of 0.047 in., and the IHLP-1616BZ-01 and IHLP-1616BZ-11 inductors offer profiles of 0.079 in.

Other features include a shielded, composite construction that is RoHS-compliant and an operating temperature range of -55°C to 125°C. Unit pricing for U.S. delivery in 10,000-piece quantities is $0.56.
Vishay Intertechnology
Malvern, Pa.
www.vishay.com.

Split-Core Current Transformers

From LEM S.A., the TT series of compact split-core ac current transformers features an innovative core material, which enables high performance at an attractive price. The core material used in the transformers is a new type of ferrite with improved magnetic permeability, allowing the accurate measurement of ac signals within an extended frequency range that includes 50 Hz/60 Hz.

The transformers feature an absolute accuracy better than 1% at the nominal current and even better for lower primary currents. The ferrite material provides an excellent linearity of better than 0.1%, even at very low levels, and the transformers have a particularly low phase shift of 1.5 degrees, ±1 degree between measured voltage and current. The hard and dense core allows very small air gaps and is insensitive to aging and temperature changes.

Two ranges of primary current measurement are available: 50 A and 100 A. The TT 50-SD measures only 1.43 in. × 1.69 in. × 1.24 in. with a 0.31-in. diameter sensing aperture for noncontact measurement. The TT 100-SD measures 1.75 in. × 2 in. × 1.44 in. with a 0.63-in.-diameter sensing aperture. Other features include a 3000 to 1 ratio and an internal output-protection circuit.
LEM USA
Milwaukee, Wis.
www.lem.com

Ultrathin Surface-Mount Inductors

The DR365-1 miniature surface-mount inductors from Datatronic Distribution are designed for applications requiring very low package height. A seated height as low as 0.047 in. above the pc board make these parts suitable for portable applications such as PDAs, mobile phones, hard drives, medical appliances and bar-code scanners. Device footprints are as small as 0.237 in².

Inductances range from 3.3 µH to 100 µH (at 100 kHz, 0.1 V); DCR, from 0.11 Ω to 2.8 Ω; and current rating, from 0.94 A to 0.20 A. Parts operate from -20°C to 80°C and meet UL94V-0 requirements for flammability. Units are priced from $0.44 each in production volumes.
Datatronic Distribution
Romoland, Calif.
www.datatronics.com

Inductor Cores

Additions to Magnetics' Kool Mµ line of segment cores enable designers to configure extremely large shapes (≥4 in.) for high-current inductors. These parts are available as either complete geometries (toroids or racetracks) or as individual interlocking segments (arcs and I segments). Segments are currently available in two sizes with outer diameters of 4 in. or 5.22 in., but new sizes are being added.
Magnetics
Pittsburgh, Pa.
www.mag-inc.com

100-VA Class 2 Transformer

Foster Transformer is offering the 100 VA SURVIVOR Class 2 transformer as the industry's highest capacity inherently limited Class 2 transformer. It features short-circuit and overload protection, which allows it to withstand a direct short circuit in excess of 15 days. Target applications include medical instruments, devices and applications, HVAC and refrigeration, control panels, appliance, vending and battery charging.

The 100VA SURVIVOR model is available with either 60-Hz or 50-Hz/60-Hz ratings. Primary input voltages include 115 V, 115 V/230 V and 200 V/230 V with 24-V output. Each size/model includes UL-recognized Class 130 (B) insulation. In addition, IEC-, EN- and CE-compliant designs are available.
Foster Transformer
Cincinnati, Ohio
www.foster-transformer.com

Configurable Transformers

Wurth Elektronik's WE-FLEX series transformers consist of six independent windings that can be connected on the pc board in several configurations, providing custom transformer flexibility at a cost closer to that of a standard component. According to the vendor, the WE-FLEX transformers will cost 10 to 20 times less than equivalent custom units. Unit pricing will depend on size and quantity.

The 25 transformers facilitate more than 500 transformer and choke variants capable of accommodating power levels from 1 W to 50 W and switching frequencies up to 1 MHz. Target applications include flyback, forward, push-pull, stepdown, stepup and SEPIC converters. Transformers are available in four sizes, with or without air gaps, and with a choice of five different air-gap lengths. Other specifications include 500-Vdc isolation and a -40°C to 125°C operating temperature range. In addition, the transformers are said to exhibit exceptionally low levels of leakage inductance.
Wurth Elektronik
Waldenburg, Germany
www.we-online.com

Surface-Mount Power Inductors

Designed for IMVP6 voltage regulator circuits, the PG0437NL series inductors eliminate many of the drawbacks associated with the iron-core inductors typically used in such applications. Constructed using ferrite cores, the PG0437NL units meet the same footprint, height and electrical parameters as the existing iron-core devices, but eliminate thermal aging, reduce core losses and increase overall battery life.

Pulse has compared the PG0437NL against competitive solutions in Dell, IBM and Apple computers using the BAPCO battery life test software. In these tests, the PG0437NL increases battery life by 4% to 6% and lowers the inductor's operating temperature by 5°C to 8°C, according to the vendor. The inductors feature a max package height of 4.5 mm, a max footprint of 12.5 mm × 11 mm and a peak current rating up to 39 A.
Pulse
San Diego
www.pulseeng.com/power

Table. Vishay Intertechnology's IHLP series specifications.

Device	Inductance	Saturation	Max DCR
‘1616AB-11	0.047 µH to 2.2 µH	3 A to 15 A	3.3 mΩ to 100 mΩ
‘1616BZ-11	0.19 µH to 4.7 µH	1.75 A to 12 A	4.5 mΩ to 150 mΩ
‘1616AB-01	0.047 µH to 1 µH	8.5 A to 32 A	3.75 mΩ to 50 mΩ
‘1616BZ-01	0.10 µH to 2.2 µH	6 A to 35 A	5 mΩ to 90 mΩ

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