Monolithic Power MOSFET and Schottky Diode Achieves 3 Milliohms On-Resistance in SO-8

The new Si4628DY SkyFET will typically be used as the low-side power MOSFET in synchronous buck converters for notebook core voltage and VRM applications, graphic cards, point-of-load power conversion, and synchronous rectification in computers and servers. Its on-resistance times gate charge figure of merit (FOM), a key indicator of performance in such applications, is 26 % better at a 10-V gate drive and 34 % better at 4.5-V than the next best device in the SO-8.

The Si4628DY is designed to improve power conversion efficiency at light loads for both mains-powered servers and battery-operated notebooks. Under light-load conditions, the MOSFET in power converters is off, and current is conducting through the Schottky diode. Because the Schottky is integrated with the MOSFET, its forward voltage drop is much lower than the voltage drop across the intrinsic body diode of the MOSFET. This results in substantially less power loss when the MOSFET is turned off during dead time in a buck converter application.

A second improvement results from the lower reverse recovery charge (QRR) of the Schottky diode compared to the QRR of the body diode of the MOSFET. Vishay Siliconix SkyFET technology reduces QRR in the device by almost 75 % from the standard MOSFET body diode, which improves converter efficiency at light loads.

Finally, integration of the Schottky into the MOSFET silicon chip eliminates the parasitic inductances that would be present if these were mounted to the PCB as individual components or if separate MOSFET and Schottky diode components were co-packaged.

The improvement in efficiency enabled by these features translates directly into lower energy usage, and thus lower electric bills for facilities like server farms and longer battery life between charges for laptop computers.