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Coupled inductors suit step-down DC/DC voltage regulators

Posted: 05 Apr 2006 ?? ?Print Version ?Bookmark and Share

Keywords:Pulse? Technitrol? coupled inductor? DC/DC voltage regulator?

Coupled inductors for DC/DC voltage regulators

Pulse, a Technitrol company, unveiled what it touts as the industry's first family of coupled inductors for non-isolated step-down DC/DC voltage regulators.

The new multi-phase coupled inductors are developed and manufactured under a license agreement with Volterra to support Volterra's VT1165M and VT1115M chipsets, which implement its patented coupled inductor topology.

Pulse's PA131xNL is a family of off-the-shelf, surface-mount, RoHS-compliant inductors, with 2, 3, 4 or 5 phases magnetically coupled together in a single part. Each phase has an equivalent transient inductance of 50nH and a magnetizing inductance greater than 250nH. Each phase is rated for 40A and has a direct current resistance of 0.5 m? maximum. These parts can accommodate a 5A current imbalance between phases, ensuring they will operate well in less-than-ideal conditions.

"The Pulse PA131xNL family, when used with Volterra's chipsets, provides lower current ripple per phase, improved transient response, and higher efficiency," said Michael Arkin, Pulse's power division product line manager. "Their lower transient inductance compared with traditional solutions reduces cost because fewer bulk capacitors are required to support high-transient-load applications such as high-performance central processing units and graphical processing units used in personal computers, workstations and servers, DC/DC power for gaming consoles, video cards, and DDR SDRAM (double data rate synchronous DRAM) memory."

In a non-coupled multi-phase DC/DC converter, each phase has an independent inductor. To improve transient response, the value of this inductor must be reduced. However, this reduction causes an increase in current ripple per phase and a decrease in efficiency. With a coupled inductor topology, all of the inductors are integrated on the same magnetic core and the interaction of the magnetic fields from each phase enables the use of a lower equivalent inductance for faster transient response without increasing the current ripple per phase. The reduction in ripple current in a coupled inductor topology compared to a non-coupled solution is approximately 50 percent for a 2-phase system, 66 percent for 3-phase, 73 percent for 4-phase, and 77 percent for a 5-phase system.

The Pulse PA131xNL family package dimensions and footprint were selected to match Volterra's requirements to enable second sourcing for the inductors while maintaining a low profile and small footprint. The sizes of the inductors are: PA1312NL18.3-by-9-by-5.2mm, PA1313NL27.3-by-9-by-5.2mm, PA1314NL36.6-by-9-by-5.2mm, PA1315NL42.7-by-9-by-5.2mm.

The inductors are available packaged in tape and reel and in trays. Pricing in 50,000 unit quantities is 45 cents per piece for the PA1312NL, 60 cents for the PA1313NL, 75 cents for the PA1314NL, and 90 cents for the PA1315NL.

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