SiC MOSFET switches with low RDS(on) reduce power losses associated with device heating, meaning they can tolerate higher current flow, thereby enabling increased power density. However, a notable additional feature of Nexperia’s SiC MOSFETs relative to devices from other manufacturers is that they have a highly stable RDS(on) even as the application temperature rises. This is particularly beneficial in applications like onboard charging (OBC) in EVs, which have a typical switching frequency of 60 kHz or higher. This stability is realized by compensating some of the positive temperature coefficients within a device to produce a flatter RDS(on) profile (Figure 1). For example, in a Nexperia SiC MOSFET with RDS(on) = 40 mΩ, at 25 °C, this value only increases by a factor of 1.5x (to approximately 60 mΩ) as the operating temperature rises to 175 °C. This is a significant improvement compared to other competing devices, which typically exhibit a 2x increase in RDS(on) to 80 mΩ or more, meaning they have to be derated for use at higher temperatures. The superior temperature stability of Nexperia’s SiC switches means engineers can use fewer devices for the same power level in an application. For example, a 40 mΩ D2PAK MOSFET can deliver almost up to 9 kW at its maximum operating temperature, while an even smaller 30 mΩ MOSFET can deliver up to 11.5 kW of power.

X.PAK top-side cooling increases degrees of freedom in designs
While this power level is already impressive, even higher power levels can be achieved from switches housed in Nexperia’s next-generation top-side cooled (TSC) packaging. This has the same die inside but leverages top-side cooling via a thermal interface, a much more effective approach than cooling through the printed circuit board on which a part is mounted. For example, while a 40 mΩ D2PAK MOSFET delivering 7.5 kW of power operates at approximately 115 °C, a similar TSC device operates at a much lower temperature of only 75 °C, a reduction of up to 40 °C. A consequence of simply changing the cooling concept in this way is that the power profile can be raised even further. For a typical 3.5 kW charger, this improved device cooling could help reduce the charging time for an EV from an hour down to 40 or even 30 minutes. Alternatively, designers have the option to increase the switching frequency in their chargers, thereby bringing the benefit of smaller passive components (especially magnetics) required. This helps to reduce not only the overall solution cost, but smaller passive components also reduce the size and weight of a charging solution, which is exceptionally important for space-constrained and EVs running operating from batteries with limited charge.
Yet another advantage of SiC MOSFET switches with higher current carrying capacity is that, since they produce less heat, they can survive for longer in the field, making them more reliable in expensive multi-year applications like EVs and solar PV. Furthermore, for lower power applications, designers have the option to use MOSFETs with a higher value of RDS(on), which typically have a smaller die and therefore can offer a more cost effective solution.