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Subject to change without notice.

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Application Considerations for SiC MOSFETs

January 2011

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Application Considerations for Silicon Carbide MOSFETs

Author: Bob Callanan, Cree, Inc.

Introduction:

The silicon carbide (SiC) MOSFET has unique capabilities that make it a superior switch when compared

to its silicon counterparts. The advantages of SiC MOSFETs have been documented extensively in the

literature [1]. However, there are some unique operating characteristics that need to be understood so

that the device can be used to its full potential.

Discussion:

The key to successfully applying the SiC MOSFET requires an understanding of the device’s unique

operating characteristics. In this section, the characteristics of Cree’s 1200V 80mΩ SiC MOSFET

(CMF20120D) will be discussed. Comparisons will be made with other similar silicon devices along with

application implications. The intention of this comparison is to illustrate the differences in operating

characteristics, not to pick the best device. The comparison silicon devices are as follows:

•

900V, 0.12

 Si super junction MOSFET (SJMOSFET) Infineon IPW90R120C3 [2]

•

1.2 kV, 20 A trench/field stop (TFS) Si IGBT Fairchild FGA20N120FGD [3]

•

1.2 kV, 20 A non-punch though (NPT) Si IGBT International Rectifier IRGP20B120U [4]

•

1.2 kV, 0.30

 Si MOSFET (Si MOS8) Microsemi APT34M120J [5]

The devices selected for comparison are representative of commercially available Si IGBTs and

MOSFETs with voltage and current ratings similar to the CMF20120D. The TFS IGBT is representative of

a low on-voltage device and the NPT IGBT is representative of a low turn-off loss device. The Si MOS8 is

representative of a commercially available 1.2kV Si MOSFET. Lastly, although not a 1.2kV device, the

900V SJMOSFET data was included for comparison purposes. All comparisons were made with

measured data except in the case of the SJMOSFET. Data sheet values were used.

Consider the output characteristics of a typical Cree CMF20120D and the Si TFS IGBT shown in Figure

1. For the CMF20120D, the transition from triode (ohmic) to saturation (constant current) regions is not

as clearly defined as it is for the Si TFS IGBT. This is a result of the modest transconductance of the

device. The modest amount of transconductance causes the transition from triode to saturation to be

spread over a wider range of drain current. The result is that the CMF20120D behaves more like a

voltage controlled resistance than a voltage controlled current source.

Discussion

Introduction

Application Considerations for Silicon Carbide

MOSFETs

Bob Callanan, Cree Inc