VISHAY'S POWERPAK POWER MOSFETS PROVIDE ON-RESISTANCE DOWN TO 2.25 MΩ
13 June 2003 - Vishay Electronic

Research conducted by Siliconix indicates that these new Vishay Siliconix devices offer the best performance of any power MOSFETs in an SO-8 footprint. The new PowerPAK devices provide on-resistance, gate-charge, and on-resistance-times-gate-charge values optimized for synchronous low-side operation and/or high-side control operation in core voltage dc-to-dc buck converters, and for secondary-side synchronous rectifiers in isolated dc-to-dc converters.

The new devices are designed for use in single or multiphase power supply circuits in server and desktop computer applications; notebook computer applications requiring 30-V devices; and in dc-to-dc converters and point of load converters in fixed telecom applications.

The PowerPAK SO-8 package provides up to 60% better power dissipation and up to 45% higher drain current than standard SO-8 devices, thanks to its order-of-magnitude lower thermal resistance. Compared with devices in the DPAK package, PowerPAK has a 53% smaller footprint area and a 55% thinner profile. The higher efficiency of PowerPAK power MOSFETs prolongs battery life in notebook computers while allowing them to run cooler and more reliably. In fixed telecom applications, the new devices' high efficiency enables design of smaller end products with less intrusive cooling requirements.

Low On-Resistance
For low-side dc-to-dc applications in computers, Vishay offers the 20-VDS/20-VGS Si7866DP and 30-VDSM/12-VGS Si7442DP, which offer on-resistance values of just 3.75 mΩ and 3.2 mΩ (4.5 VGS), values that are 25% and 27% lower than those offered by the best competing devices. The new Si7880DP (30 VDS/20 VGS) features an exceptionally low on-resistance of just 4.25 mΩ, 20% lower than the best competing devices. All of these low-side, low-rDS(on) devices have an optimized Qgd/Qgs of less than 1 to help prevent the low-side MOSFET from going into a "shoot-thru" situation during which both the high and low side are on, creating a short from the input voltage to ground.

For fixed telecom applications, the lowest MOSFET on-resistance is offered in the 12- to 40-V range - including key telecom rectification voltages (20 VDS and 30 VDS), for use in a variety of topologies. In addition to the Si7866DP, Si7442DP and Si7880DP, the table below summarizes the Si7858DP, Si7862DP, Si7864DP, Si7868DP, Si7458DP, and Si7884DP, which offer the lowest on-resistance for their respective voltage grades.

With their exceptionally low on-resistance values, these PowerPAK SO-8 devices provide low conduction losses and increased efficiency for prolonged battery life and/or cooler system operation.

Low On-Resistance-Times-Gate-Charge Product
For power conversion applications in computers, the 30-VDS/20-VGS Si7860DP offers the lowest on-resistance-times-gate-charge product in the industry - just 143. A Qgd/Qgs of less than 1 prevents "shoot-thru" conditions, while the Si7860DP's industry-leading performance allows designers to use the same power MOSFET for both the low and high side, thereby reducing the cost and complexity of the assembly process.

For fixed telecom applications, the Si7368DP, Si7366DP, Si7864DP, Si7860DP, and Si7884DP shown in the table below are optimized for high switching frequencies.

The Si7806DN operates with minimal switching losses to maximize efficiency in low-duty-cycle dc-to-dc applications. In fixed telecom and high-side computer operation, the 30-VDS/20-VGS Si7806DN offers an exceptionally low gate charge of just 8.5 nC (4.5 VGS) and a low on-resistance-times-gate-charge product of just 149 in the smaller PowerPAK 1212-8 package, just 1/3 the size of the PowerPAK SO-8 package.

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