q101fets| Application Note
New Power MOSFET Technology with Extreme Ruggedness and Ultra- Low RDS(on) Qualified to Q101 for Automotive Applications
by Anthony Murray, Harold Davis, Joe Cao, Kyle Spring, Tim McDonald International Rectifier Abstract An extremely rugged technology has been developed for ultra low RDS(on) applications. This paper compares the R.A product and ruggedness of this new technology with a previous generation technology. A factor of 2 improvement in R.A product and a factor of 5 improvement in avalanche energy have been demonstrated. The paper also presents a scheme to reliably rate devices under repetitive avalanche conditions. undesirable turn-on by minimizing the parasitic base resistance (Rb) under the N+ source and also ensuring the source is always shorted to the P body. The stripe versus cell structure for the two technologies in question is shown in Figure 1, along with a cross-section of a power MOSFET illustrating the inherent parasitic bipolar transistor.
Gate Contact Regions Gate
1. INTRODUCTION Today's automotive applications demand improved system efficiency at low cost. As system size shrinks and frequency increases, the performance demand on components rises rapidly. Trends have been towards lower R DS(on) parts, resulting in fewer components and improved efficiency and performance. However, as die size has decreased and switching frequency increased, the ruggedness requirements on today's power MOSFETs has significantly increased due to increased power density. Modern systems require parts to withstand repetitive high voltage transients generated by di/dt and parasitic inductance, sometimes forcing devices into a repetitive avalanching condition. A technology with extreme ruggedness has been developed, while maintaining ultra low R DS(on) . This technology is ideal for electronic power steering, starter alternator and direct battery control automotive applications.
P- body contact
P+
N+ PN- Epi N+ Substrate
N+ P+ P-
Figure 1. Photo of stripe versus cell topologies and cross-section of power MOSFET showing parasitic bipolar transistor.
2. TECHNOLOGY 3. ELECTRICAL RESULTS The technology described here is based on International Rectifier's advanced planar stripe topology. The stripe topology results in much higher ruggedness compared to a cell topology, since the P-body in each cell is continuously contacted along the entire strip length, rather than locally in the case of a cell design. This results in virtual immunity of the parasitic bipolar transistor from 3.1 R.A Product The specific on resistance or R.A product for the new technology is plotted in Figure 2 versus rated breakdown voltage. All values are normalized to the old cell technology and measured at a gate drive voltage of Vgs=10V. Package resistance has been
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