Wireless Systems Design

Cell Phones Reap Power-MOSFET Benefits

Mobile devices require low-power electronics like the new TrenchFET power MOSFETs. Built on a patent-pending p-channel technology, these packages can reduce device on-resistance to as low as 5 milliohms in the PowerPAK SO-8 configuration. When used as load switches, the p-channel power MOSFETs use this technology to reduce power consumption. They also cut the board area required for power components in cell phones, PDAs, notebook computers, and other compact battery-operated products.

In such systems, p-channel MOSFETs are used to turn off features that are not being used. Examples include the user display screen or device power amplifiers. However, these features also can be turned off by switching the system from an active to a sleep mode. Either way, the result is battery-life savings.

This device family is offered in 12-V, 20-V, and 30-V single and dual versions. Each version comes packaged in LITTLE FOOT small-outline package types (SO-8, TSSOP-8, TSOP-6, and SOT-23). They also come in the leadless, thermally enhanced PowerPAK SO-8 and 1212-8 packages.

The on-resistance for the −12-V Si7407DN, which is packaged in the 3.3-×-3.3-mm PowerPAK 1212-8, is just 12 milliohms at −4.5 V. That translates into a 25% improvement over the previous state-of-the-art for this package type. In addition to saving space, the PowerPAK 1212-8 dissipates up to 3.8 W of power—nearly double the level of any MOSFET device with a TSSOP-8-size footprint or smaller. Thermal resistance of just 1.9°C per Watt allows space requirements to be reduced in portable electronics without increasing "hot spots."

The −20-V Si4423DY is the first SO-8 device to utilize this new p-channel technology. It is rated for 7.5 milliohms at 4.5 V and 11.5 milliohms at 1.8 V. These figures equal improvements of 12% and 18%, respectively, over the next-best devices.

The Si7451DP is the first −30-V, p-channel device in the PowerPAK SO-8. On-resistance for the device is just 5 milliohms at 10 V, with a maximum VGS of 25 V. This higher gate-to-source voltage provides an extra safety margin in 20-V-bus notebook-computer applications.

Among the first LITTLE FOOT TSOP-6 devices built on p-channel technology is the single-channel, −30-V Si3483DV. This device is rated for maximum on-resistance of 53 milliohms at 4.5 V—a 28% improvement over the next-best device on the market. Maximum current handling for the device is 6.2 A.

Samples and production quantities of the new p-channel power MOSFETs are available now. Lead times of 8 to 10 weeks exist for larger orders. Pricing for U.S. delivery ranges from $0.25 to $1.50 in 100,000-piece quantities.

Vishay Siliconix
2201 Laurelwood Rd., Santa Clara, CA 95054; (619) 336-0860, www.vishay.com.

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