Dynamic Characterization Platform for SiC Power MOSFETs and Schottky Diodes

The Dynamic Characterization Platform (DCP) from Littelfuse enables design engineers to characterize the high-performance silicon carbide (SiC) MOSFETs and diodes offered by Littelfuse with high accuracy. The DCP is designed to:

  • Measure
    • MOSFET switching losses, switching times, and gate charge accurately.
    • Schottky Barrier Diode (SBD) and body diode reverse recovery accurately.
  • Provide an informed reference design for gate drive and power loop PCB layout.
  • Provide informed recommendations for gate drive layout and components.
  • Promote streamlined device validation and quicker design cycles.

Functionality highlights of this evaluation kit include: It is designed for TO-247-3L SiC MOSFETs and TO-220-2L SiC Schottky barrier diodes; The power loop and gate drive circuitry is optimized for ultra-fast dV/dt and dI/dt events; And there are integrated input signal and measurement probe interface connections.

Below is a block diagram of the DCP. It is arranged in a single-phase leg configuration that accommodates two SiC MOSFETs and optional anti-parallel Schottky diodes. Each MOSFET has its own gate driver circuit, including individual digital isolators, current boosters, and isolated power supplies.

DCP block diagram

Although SiC MOSFETs behave much like silicon MOSFETs and are quite simple to drive, designers must pay special attention to certain aspects in order to harness the full advantage of these fast switching devices. Littelfuse observes that the switching behavior of the MOSFETs can be severely impaired by parasitic inductances stemming from poor PCB layouts. These parasitic inductances, coupled with the fast dV/dt and dI/dt characteristics of the SiC MOSFETs, can lead to a number of undesirable effects, including voltage and current overshoot, increased switching losses, and system instability.

Additionally, using traditional silicon IGBT based techniques to characterize the switching behavior of SiC MOSFETs may result in erroneous conclusions about switching losses due to insufficient measurement probe bandwidth, equipment inadequacy, etc.

The DCP from Littelfuse is designed to characterize SiC MOSFET and diode switching losses via the double-pulse technique. It can also be used to characterize other typical dynamic parameters provided in MOSFET and diode datasheets, such as switching times, gate charge, and reverse recovery. Measuring these parameters for SiC devices requires an optimized board layout and precise voltage/current sensing techniques, and is enabled by the DCP.

Littelfuse Inc.
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