IR qualifies DirectFET MOSFET package for automotive designs

EDN Europe, 25 Jan 2010

International Rectifier has introduced a new variant of its DirectFET package for power switch devices, with features optimised for automotive designs. DirectFET is a metal can package that holds a single FET die. It takes the form of an inverted dish, of the same depth as the die thickness, and IR uses it for vertical FETs, with source and drain connections on front and back of the silicon. The back face of the die attaches to the inside of the can, and the folded tabs of the can then provide a low-resistance connection down to the printed-circuit board. The top surface of the die is in the same plane as the package tabs, so that surface of the die also connects directly to the PCB. This construction, IR says, provides low electrical resistance to both top and bottom die connections, very-low inductance paths, and high thermal conductivity to both top and bottom of the die.
DirectFET2, making its first appearance housing the AUIRF7739L2 power MOSFET, and paried with the smaller AUIRF7665S2 switch, now adds AEC-Q101 qualification to the combination of high power density, dual-sided cooling and low parasitic inductance and resistance. IR says it will expand the automotive-qualified range to include parts optimised for ultra-low on-state resistance (RDS(on)), gate charge (Qg) or logic level operation. It also quotes improved moisture-sensitivity-levels (MSL1) for the automotive environment. Prior to this revision, IR acknowledges that the DirectFET format was “not suitable for automotive qualification”, but has now resolved all the relevant issues.
The AUIRF7739L2, in the new large can – DirectFET2 is a physically larger package than the original DirectFET, which IR sells into space-constrained power conversion applications – yields an RDS(on) figure of 0.7mΩ (typical) at 40V. The package measures 9.03 x 6.85 x 0.68mm. Although it is a bigger version of the DirectFET package, it is still 60% smaller in outline (while accommodating a 30% larger die) and 85% lower profile than a D2PAK, IR says. You might use it, the company suggests, in Electric Power Steering (EPS), battery switches and Integrated Starter Alternators (ISA) in Micro Hybrid Vehicles, and chassis, drive train and power train systems.
The AUIRF7665S2 uses a small-can outline and is optimised for very low gate charge with low parasitics for fast and efficient switching. The DirectFET2 MOSFET is suitable for automotive switching applications including the output stage of Class D Audio amplifiers as well as DC-DC converters and fuel injection systems, with 51-mΩ, 100-V, and 8.3-nC gate charge specifications. Pricing for the AUIRF7739L2 and the AUIRF7665S2 begins at US $2.60 each and US $0.46 each respectively in low volume quantities.