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This datasheet for a Rohm SCT3017 silicon-carbide N-channel power MOSFET's Safe Operating Area only extends as fast as 100µs. Why no trace for 10µs?

Is it because with an expected gate charge of 170nC, the 4Ω of gate resistance limits the transition rate?

\$\tau=\text{2884pF}\cdot 4\Omega=11.5\text{ns}\$ for 63% charge, \$5\tau\$ in 57.7ns. That's fast enough for 10µs pulses, no?

The blue line is 384VDC. 10A is do-able with a \$\text{P}_\text{W}\$=100µs, while 30A is on the edge. 100A is out-of-the-question at 100µs, but what about 10µs?

Rohm SCT3017 N-channel SiC power MOSFET SoA

rdtsc
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  • Not necessarily. Material imperfection cones into play more and more. – DKNguyen Aug 21 '21 at 18:38
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    I would guess at some point it remains constant or actually starts reversing again, due to the inability to conduct that incredibly short-term pulse of thermal energy through whatever thickness and material it has to move. – MadHatter Aug 21 '21 at 18:42
  • I was wondering if maybe the bond wires inside couldn't take that kind of peak current. – rdtsc Aug 21 '21 at 22:20
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    @rdtsc Not that simple. It's hot spots due to imperfections in the silicon developing faster than the heat can spread out. – DKNguyen Aug 22 '21 at 01:30

1 Answers1

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Can SiC SoA rating be extrapolated for faster pulse widths?

No it can't. I've recently fallen foul of this using a Genesic 1200 volt SiC MOSFET and, well, darn me, but the device failed and I had to eat humble pie and recognize that I had done what you might be thinking of doing. I don't make many mistakes and, the unit was a prototype (so no great loss) but, a big red face: -

enter image description here

The clue should have been in the price and I ended-up going with an ON semi SiC MOSFET and boy, does that device deliver the goods (at three times the price but who cares if it does the job and doesn't squirm on fast heavy-duty pulses).

To punish myself for my indiscretion I wrote out the full version of RTFD 1,000 times on paper.

The clues in your data sheet are these: -

enter image description here

  • Maximum stated power dissipation is 427 watts and this ties in fairly nicely with the 100 ms graph constant power slope (450 watts)
  • Why wouldn't a manufacturer provide information at power ratings above 10 kW if the device is capable of higher peak powers?

After my equivalent exercise I was left wondering what target market area is serviced by these types of SiC MOSFET because anyone designed a power switching circuit will default to thinking about 100 kHz switching frequencies. My conclusion is that someone somewhere must be using them for something but it can't be a mainstream application.

Andy aka
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