What should be noted when setting SiC MOSFET gate voltage (V_GS)?

i) Within the absolute maximum ratings
Use V_GS within the absolute maximum rated V_GS=+25,-10V including the surge voltage and considering the derating.

ii) Set V_GS at turn-on to 18V or higher
A disribution map of the on-resistance (R_DS(ON)) is shown in Figure 1. In V_GS=15V map shown on the left, the on-resistance increases rapidly. By setting V_GS to 18V or higher, the variation with low on-resistance can be reduced.

iii) Set the gate voltage at turn-off to 0V or less
V_th – T_a curve is shown in Figure 2. The lower limit of gate threshold voltage (V_th) is 3.0V at T_a=25°C. In addition, as shown in the temperature characteristic curve, V_th has a negative temperature coefficient and drops 1.2V at 25°C ⇒ 175°C. Confirm the gate voltage does not exceed V_th and not be turned on incorrectly during the off-period due to the voltage fluctuations during actual operation. 

iv) Charge the gate-source capacitance sufficiently with the gate charge.
The gate-source capacitance must be charged with gate charges to rise V_GS to turn on. For TW060Z120C, the gate charge at V_GS =18V is typically 46nC as shown in Table1. Apply the gate current that can sufficiently charge the gate charge at the frequency to be used.

Table 1. Gate charge characteristics in data sheet ＠T_a=25℃ (TW060Z120C)

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