News and New Products

MOSFETs get their 15 minutes of fame at APEC

By Margery Conner, Technical Editor -- EDN, 3/14/2008

One thing you can count on at the power-conversion industry’s annual APEC (Applied Power Electronics Conference) is that MOSFETs will feature prominently. This year’s conference, which took place last month in Austin, TX, was no exception, with new announcements from Infineon, Fairchild, and Toshiba, among others.

Infineon is claiming an industry-first with its 900V superjunction MOSFETs, which target high-efficiency SMPS (switched-mode-power-supply), industrial, and solar-energy applications. Infineon claims that the CoolMOS power-MOSFET family overcomes the “silicon limit,” a characteristic of MOSFET semiconductors in which doubling of voltage blocking capability leads to a fivefold increase in on-resistance. In overcoming the silicon limit, the CoolMOS devices achieve the industry’s lowest on-resistance per package type: 0.12Ω in a TO-247 package, 0.34Ω in a TO-220 package, and 1.2Ω in a D-Pak. The company claims that these figures are at least 75% lower than those for conventional 900 V MOSFETs. The devices offer a figure of merit, which the company calculates as on-resistance times the gate charge, as low as 34Ω-nC, yielding low conduction, driving, and switching losses, and increased efficiency. The volume price for a 120-mΩ part in a TO-247 package is less than $3.50.

Using discrete MOSFETs on a board can increase manufacturing costs and resistance between parts. Fairchild attacks this problem by incorporating two PowerTrench MOSFETs and a high-current gate driver into its EPM15-packaged Power-SPM FPP06R001, which replaces as many as 10 discrete components. Fairchild claims the advanced package accounts for 10% lower on-resistance and 16% lower stray inductance than comparable discrete approaches. The devices cost $5.

Toshiba announced a family of high-speed switching MOSFETs, which the company based on its UMOS VI-H sixth-generation trench process. The new devices enable increased power efficiency by lowering on-resistance and increasing switching speed through lower gate charge and lower gate resistance. The new MOSFETs also feature aluminum-strap connections instead of conventional wire-bond technology to further reduce on-resistance. The devices will find use as low-side MOSFETs in dc/dc-converter applications. Features include a maximum drain-to-source voltage of 30V, a maximum drain current of 50A, and a typical on-resistance of 2 mΩ. Packaging options include a low-profile SOP Advance measuring 5×6×0.95 mm. Prices start at 65 cents each.

The importance of using discrete semiconductors in power-efficient designs is becoming increasingly clear, and it makes you wonder whether companies such National Semiconductor, which spun its discrete analog parts to Fairchild several years ago, and Texas Instruments, would be better off with their own MOSFET groups to best tailor their switching components to their control electronics.