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TO-247N(-4L) Half-Bridge Evaluation Board
User’s Guide
© 2022 ROHM Co., Ltd.
No. 63UG0
60E
Rev.001
2022.2
11.2 Surge suppression effect of protective circuit
A double-pulse test was conducted by connecting SCT4090KR in a bridge configuration and switching the high-side (HS), and
the following is an example of how the protective circuit reduces the V
GS
surge voltage. Figure 24(a) shows the measurement
circuit and (b) shows the measurement waveform.
The external gate resistor R
G_EXT
is 3.3Ω. The top waveform is V
GS
on the H-side, the second is V
GS
on the L-side, the third is
V
DS
on the H-side, and the bottom waveform is I
D
on the H-side. The gate-source pin surge is positive on the H-side during turn-
on, and negative on the HS and L-sides during turn-off. Separate application notes (*1),(*4) on the causes of surges have been
prepared, so they are not discussed in detail here. However, if no protection circuit is mounted (No Protection), a surge
exceeding the rated gate voltage of the MOSFET may occur.
(a)
Measurement circuit
(b)
Measurement waveform
High
Side
Low
Side
V
G
V
SW
L
(HS)
(LS)
E
R
G_EXT
R
G_EXT
Figure 25 Effect of protection circuit (SCT4090KR)
■ Measurement conditions
DUT: SCT4018KR
E: 800V
L: 250µH
Drain current: Approx. 80 A
Pulse width: 2.5µs
R
G_EXT
: 3.3Ω
Evaluation board: PCB005P Rev.C
