New LV Wide SOA Power MOSFET technology for Linear Mode operation

Many applications, especially in the Telecom (hot-swap + PoE) and Automotive field, require Power MOSFET robustness in linear mode. Modern devices have been designed for ever-decreasing on-resistance and very high current capability at the expense of reduced FBSOA (Forward-biased Safe Operating Area). Linear Mode operation highlights a different scenario than a switched-mode application where the design is usually driven by dynamic and static power losses. If the device is operated in Linear Mode, the power dissipation is quite high because it works with high voltage drop and high current that could result in rapid increase of the junction temperature that may lead the Power MOSFET to thermal runaway or in other words to an unstable condition that occurs when the junction temperature increases without control until device failure occurs. The objective of the following paper is to evaluate the key requirements of a Power MOSFET working in a hot-swap application and to compare the latest advanced LV technology, not suitable for it, with the new tailored technology designed by ST to satisfy the harsh requirement of the Linear Mode Operation.