The IRF6621/ I R F 6 6 1 2 s y n c h r o n o u s buck converter from International Rectifier is a 30V MOSFETbased chipset for 14 to 18A multiphase dc/dc s u p p l i e s , primarily in notebook PCs. Consisting of a control MOSFET (IRF6621) and a s y n c h r o n o u s MOSFET (IRF6612), each optimized for their role in the buck converter topology (reduced switching losses for the former; low conduction losses for the latter), designs using this chipset can reach 87% efficiency at 18A per phase, and 90% at 10A. The IRF6621 has Qg of 11 nC and Qgd of 3.8 nC; the IRF6612 has 3.4 mohm Rds(on) at 4.5V. In 10,000- unit quantities, the MOSFETs are $1.03 and $0.76, respectively. By Bill Schweber
