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MOSFETs in leadless packages increase power density

Reduced on-resistance, gate charge and package parasitics cut losses

Infineon has extended its range of OptiMOS 3 MOSFETs to include parts with breakdown voltages of 40, 60 and 80V, claiming the lowest on-state resistance at those voltages in leadless SO-8-derived packages. The FETs come in the SuperSO8 and Shrink SuperSO8 (S3O8) outlines that can halve board area for a given power compared to TO-style packages. The range now covers 20 to 150-V devices; as well as low on-resistance, Infineon says that the switches have very low gate charge and Miller-charge specifications. According to a company spokesman, the 40-V parts will find applications in automotive designs, and the 80-V switches in synchronous rectification. RDS(on)max is as low as 1.8 milliohms for OptiMOS 3 40V, 2.8 milliohms for 60V and 4.7 milliohms for 80V. The FOM (figure of merit, calculated as on-state resistance times gate charge) of these devices is as much as 25% better than that of similar parts in standard TO packages, enabling even faster switching while minimising switching and gate-drive losses. The package inductance of the SuperSO8 package is less than 0.5 nH compared to 5 to 10 nH for a TO-220, further improving overall efficiency and minimising ringing under switching conditions. Thermal resistance is 1° K/W to the PCB; you can also apply top- and double-sided cooling, for a continuous current rating of 100 A.
Members of the OptiMOS 3 60V family are now available in production quantities, and Infineon is sampling 40V and 80V devices. An OptiMOS 3 60V, with RDS(on) of 2.8 milliohms in an SuperSO8 package, costs €0.64; the 80V version, with RDS(on) of 4.7 milliohms in an SuperSO8 package, €0.70; a 6.7 milliohm OptiMOS 3 60V in an S3O8 package is € 0.38), and a 12.3 milliohm OptiMOS 3 80V in an S3O8 package, €0.42 (all 10,000).