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Hi Itsu,
The strange thing is that your capacitance tests show pretty close values for the MSC035SMA170B4 as per the data sheet includes.
And the capacitance tests on the C2M0045170D type show very low pF values by the same C meter. Of course , the capacitances depend very much on the voltage levels between the MOSFET pins and the data sheets show the curves in the function of the drain-source DC voltage, they used 25 mV AC at 1 MHz frequency. (I do not think your 10 kHz test frequency is a problem here. )
Basically these Silicon Carbid MOSFETs have very similar behaviour capacitance wise in the function of the drain source voltage to that of "normal" power MOSFETs. i.e. as the drain source voltage increases, all the capacitances decrease with respect to their zero bias capacitance values.
Probably the capacitance measurement can be done by applying a static DC bias across the drain source pins via the 470 k or even 1 MegaOhm drain resistor and use the C meter between the drain and source via a coupling capacitor of say 1 nF in series with the meter. The gate and source pins should be connected together (Vgs=0).
I attach below the relevant Figures from both data sheets.
Perhaps the answer from the manufacturer Lee turned to may reveal some explanation on the long turn off time issue.
Gyula
Edit: I wrote applying static DC bias across the drain source pins but of course a variable DC is to be used. Normally at zero voltages all the capacitances are at their highest values (some nF) and these decrease as the voltage levels increase, the higher the voltage levels (up to the max rated ones) the lower the capacitances go down. Varicap diodes behave like this too.
« Last Edit: 2023-05-01, 13:56:54 by gyula »
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