It seems every time a new MOSFET is introduced, the supplier focuses almost exclusively on its RDS(on) and gate charge (Qg) as if they’re the only things that matter. While undeniably important, it’s equally essential – if not more so – to also look at the body diode and if it has a soft or snappy recovery from voltage overshoots.
If the body diode can recover softly, then product designers can reduce or eliminate the number of snubbers in the design. However, if the body diode has a snappy recovery, the product design will clearly require snubbers – potentially many of them – to dissipate overshoots and the resulting electromagnetic interference (EMI).
Reducing or eliminating snubbers has several benefits. Firstly, system power loss can be reduced, and sometimes substantially. There are obvious bill-of-materials (BOM) savings as well since you won’t be paying for snubbers you don’t need. Additionally, board space can be freed up, and in some cases, the board itself can be made smaller, which has obvious packaging advantages.
Recognizing the importance of the body diode, we engineered our new FDMS86181 100V Shielded Gate PowerTrench® MOSFET with the best performing body diode in its class, having reduced voltage overshoots and EMI. Complementing this, we’ve reduced the Reverse Recovery Charge (Qrr) of the FDMS86181 by 50 percent over its predecessor to give it the lowest Qrr of any MOSFET in its voltage rating.
The FDMS86181’s unique combination of a soft recovering body diode with exceptionally low Qrr gives product designers another potential benefit beyond the reduction of snubbers.
Instead of accepting voltage overshoots as inevitable and using MOSFETs with higher breakdown voltages and a higher RDS(on) than necessary, designers can specify our 100V FDMS86181 rather than using a 120V or 150V MOSFET. This approach potentially has some very desirable cost and performance advantages.
The FDMS86181 is the latest addition to our PowerTrench MOSFET family, and it benefits from all that we’ve learned in the 25 years since we pioneered PowerTrench MOSFET technology. We’ve worked hard to ensure it provides substantial benefits that manufacturers can take advantage of to improve the reliability and ruggedness of power supplies, motor drives and other applications that require a 100V MOSFET. This is the first of a wide family of devices using this technology in multiple packages.
You can learn more about the FDMS86181 and our other PowerTrench MOSFETs at fairchildsemi.com/powertrench.