2N7635-GA Datasheet, PDF (7/10 Pages) GeneSiC Semiconductor, Inc. – Normally – OFF Silicon Carbide Junction Transistor

2N7635-GA
B: High Speed Driving
For ultra high speed 2N7635-GA switching (tr, tf < 20 ns) while maintaining low gate drive losses the supplied gate current should include a
positive current peak during turn-on, a negative voltage peak during turn-off, and continuous gate current IG to remain on.
An SJT is rapidly switched from its blocking state to on-state, when the necessary gate charge for turn-on, QG, is supplied by a burst of high
gate current until the gate-source capacitance, CGS, and gate-drain capacitance, CGD, are fully charged. Ideally, the burst should terminate
when the drain voltage has fallen to its on-state value in order to avoid unnecessary drive losses. A negative voltage peak is recommended for
the turn-off transition in order to ensure that the gate current is not being supplied under high dV/dt due to the Miller effect. While satisfactory
turn off can be achieved with VGS = 0 V, a negative VGS value may be used in order to speed up the turn-off transition.
B:1: High Speed, Low Loss Drive with Boost Capacitor
The 2N7635-GA may be driven using a High Speed, Low Loss Drive with Boost Capacitor topology in which multiple voltage levels, a gate
resistor, and a gate capacitor are used to provide current peaks at turn-on and turn-off for fast switching and a continuous gate current while in
on-state. As shown in Figure 16, in this topology two gate driver ICs are utilized. An external gate resistor RG is driven by a low voltage driver
to supply the continuous gate current throughout on-state.and a gate capacitor CG is driven at a higher voltage level to supply a high current
peak at turn-on and turn-off. A 3 kV isolated evaluation gate drive board (GA03IDDJT30-FR4) from GeneSiC Semiconductor utilizing this
topology is commercially available for high and low-side driving, its datasheet provides additional details about this drive topology.
V_GH
Gate Signal
V_GL
C_G
R_G
D
I_{G G}
Gate
S
SiC SJT
Figure 16: High Speed, Low Loss Drive with Boost Capacitor Topology
B:2: High Speed, Low Loss Drive with Boost Inductor
A High Speed, Low-Loss Driver with Boost Inductor is also capable of driving the 2N7635-GA at high-speed. It utilizes a gate drive inductor
instead of a capacitor to provide the high-current gate current pulses IG,on and IG,off. During operation, inductor L is charged to a specified IG,on
current value then made to discharge IL into the SJT gate pin using logic control of S1, S2, S3, and S4, as shown in Figure 17. After turn on,
while the device remains on the necessary steady state gate current IG,steady is supplied from source VCC through RG. Please refer to the article
“A current-source concept for fast and efficient driving of silicon carbide transistors” by Dr. Jacek Rąbkowski for additional information on this
driving topology.³
VCC
S₁
VCC
S₂
L
VEE
S₃
RG
S₄
SiC SJT D
G
S
VEE
Figure 17: High Speed, Low-Loss Driver with Boost Inductor Topology
3 _{– Archives of Electrical Engineering. Volume 62, Issue 2, Pages 333–343, ISSN (Print) 0004-0746, DOI: 10.2478/aee-2013-0026, June 2013}
Dec 2014
http://www.genesicsemi.com/high-temperature-sic/high-temperature-sic-junction-transistors/
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