UC3842B, UC3843B, UC2842B, UC2843B, NCV3843BV
V
V
in
CC
I
B
7(12)
V
in
+
0
5.0V Ref
Base Charge
Removal
+
-
-
7(11)
+
-
C1
R
g
Q1
Q1
6(10)
6(10)
S
R
Q
5(8)
3(5)
5(8)
3(5)
Comp/Latch
R
S
R
S
Series gate resistor R will damp any high frequency parasitic oscillations
g
The totem pole output can furnish negative base current for enhanced
transistor turn-off, with the addition of capacitor C .
1
caused by the MOSFET input capacitance and any series wiring inductance in
the gate-source circuit.
Figure 28. MOSFET Parasitic Oscillations
Figure 29. Bipolar Transistor Drive
V
in
V
CC
8(14)
R
Bias
7(12)
R
Isolation
Boundary
5.0V Ref
Osc
4(7)
+
-
+
V
Waveforms
+
GS
1.0 mA
2R
+
0
-
7(11)
Q1
+
-
R
EA
2(3)
1(1)
0
-
50% DC
25% DC
6(10)
5(8)
S
R
MCR
101
2N
3905
V
* 1.4
(Pin1)
3ĂR
N
S
N
5(9)
Q
Ă ǒ Ǔ
I k +
p
S
p
2N
3903
R
3(5)
Comp/Latch
C
R
N
S
S
N
P
The MCR101 SCR must be selected for a holding of < 0.5 mA @ T
. The simple two
A(min)
transistor circuit can be used in place of the SCR as shown. All resistors are 10 k.
Figure 30. Isolated MOSFET Drive
Figure 31. Latched Shutdown
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