Designing Greener, Smaller Power Supplies with Power MOSFET Family Devices

TrenchFET® IV is the latest generation in the TrenchFET power MOSFET family. Compared to TrenchFET III, TrenchFET IV has reduced on-resistance (RDS(ON)) and gate charge (QG, QGD) values, reducing losses in synchronous DC/DC converters. In the past, lower RDS(ON) was usually traded off with higher gate charge. But TrenchFET IV uses a new high-density design that achieves optimized gate charge levels and lower RDS(ON). Table 1 compares the TrenchFET IV product SiRA00DP and the previous state-of-the-art SiR812DP TrenchFET Gen III power MOSFET. The new device has 30% and 39% lower RDS(ON) and Qg, respectively.

Improving the on-resistance and gate charge product (figure of merit, FOM) can not only improve the overall system efficiency, but also enable the DC/DC converter to achieve higher power density and higher switching frequency. To verify the efficiency improvement from TrenchFET III to TrenchFET IV, we tested two TrenchFET IVs, SiRA14DP and SiRA04DP, using a 19V input voltage to achieve a 1V output.

Figure 1 demonstrates the use of a TrenchFET IV as the “control FET” in a synchronous buck converter, where the TrenchFET IV is 0.5% more efficient than the TrenchFET III at currents up to 27A. Figure 2 shows the efficiency improvement of using a TrenchFET IV as the “sync FET” in a synchronous buck converter. Switching to a TrenchFET IV improves efficiency by more than 1.5% and each MOSFET can handle more output current. The higher output current handling capability enables designers to reduce the number and size of MOSFETs required to handle a given current level.

Figure 3 shows that TrenchFET IV products can achieve higher efficiency in a 66% smaller package than TrenchFET III. The SiSA04DN is a TrenchFET IV device in a PowerPAK® 1212-8 package with a footprint of 9mm2, and the SiR818DP is a TrenchFET III device in a 30mm2 PowerPAK® SO‑8 package. TrenchFET IV reduces power losses by up to 17% over TrenchFET III products.

The improvement in losses is shown in Figure 4, especially at the peak current of 15A where the loss is significantly reduced.

in conclusion:

TrenchFET IV products are used in synchronous buck converters to improve overall system efficiency and power density. The higher performance of these products also enables smaller designs and the potential for fewer components . In short, the benefits of these products are greener, more efficient and smaller power supply designs.