Wireless Systems Design

Power MOSFETs Set On-Resistance Records

Designers of portable equipment must ensure battery protection while squeezing in on-resistance to extend battery life. To help them achieve this goal, Siliconix, Inc., a subsidiary of Vishay Intertechnology, Inc., has released five n-channel TrenchFET power MOSFETs. The devices are aimed at battery-protection applications in one- and two-cell lithium-ion and -polymer battery packs and circuitry.

The common-drain devices protect against overcurrent and overvoltage conditions during charging. Thanks to a reverse blocking function, they also prevent discharge back into the ac source once the battery is fully charged. Their extremely low on-resistance helps to prolong battery life. As a result, they extend talk and standby times in portable equipment like cell phones, pagers, and PDAs.

Among the new devices are two chip-scale MOSFETs offering industry-low on-resistance-per-footprint area. For applications that require the lowest possible on-resistance, Vishay Siliconix provides the MICRO FOOT Si8900EDB. It boasts an on-resistance of 24 milliohms at a 4.5-V gate drive. The average footprint for the device is 8.07 mm2. For designers needing smaller designs, the MICRO FOOT Si8902EDB flaunts an on-resistance of 45 milliohms. The gate for this device is also 4.5 V. Yet it flaunts an average footprint of only 3.68 mm2.

The bidirectional, 20-V MICRO FOOT devices have a profile of just 0.62 mm. They fit easily on the slim printed-circuit boards demanded by narrow handheld electronics. By relying on a solder bump process and proprietary techniques developed by the company, the devices eliminate the need for an outer package to encase the power-MOSFET die. The Si8900EDB and the Si8902EDB both provide 4000-V ESD protection.

The other three MOSFETs in the family serve different applications. For applications that require a 30-V device, for instance, the bidirectional Si6876EDQ power MOSFET offers low on-resistance of 30 milliohms at a 4.5-V gate drive. If a lower breakdown voltage is acceptable, the 20-V Si6880EDQ steps in with an on-resistance of 18 milliohms at a 4.5-V gate drive. It's specified for operation down to 1.8 V. Both of these devices come in a TSSOP-8 package. They feature ESD protection of 4000 V.

Lastly, the 30-V Si7902EDN serves applications that require enhanced thermal performance. This dual common-drain power MOSFET has an on-resistance value of 28 milliohms at a 4.5-V gate drive. Its ESD protection is 3000 V. The device is available in a PowerPAK 1212-8 package. At 1.07 mm, it has a very low profile. The footprint area also is small at 10.56 mm2, making it roughly half the size of the TSSOP-8.

All five power MOSFETs are rated for operation over a temperature range of −55° to +150°C. Samples and production quantities of the Si8900EDB, Si8902EDB, Si6876EDQ, Si6880EDQ, and Si7902EDN are now available. Lead times are 12 weeks for larger orders. In the U.S., pricing ranges from $ .60 to $1.15 for delivery in 100,000-piece quantities.

Vishay Siliconix
2201 Laurelwood Rd., Santa Clara, CA 95054; e-mail: [email protected], www.Vishay.com.

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