UC3842B, 43B UC2842B, 43B
Figure 28. Bipolar Transistor Drive
Figure 29. Isolated MOSFET Drive
I
B
V
in
V
V
in
CC
+
0
7(12)
Isolation
Boundary
Base Charge
Removal
–
5.0V Ref
+
–
V
Waveforms
+
GS
C1
+
0
–
7(11)
Q1
+
–
Q1
0
–
6(10)
50% DC
V
25% DC
6(10)
5(8)
S
R
1.4
5(8)
(Pin1)
N
N
S
Q
I
k
p
3
R
S
p
R
3(5)
Comp/Latch
3(5)
R
S
C
R
S
N
S
N
P
Thetotempoleoutputcanfurnishnegativebasecurrentforenhancedtransistor
turn–off, with the addition of capacitor C
.
1
Figure 30. Latched Shutdown
Figure 31. Error Amplifier Compensation
From V
2.5V
O
+
8(14)
R
1.0mA
R
i
2R
Bias
2(3)
R
EA
R
C
R
f
f
R
d
Osc
1(1)
4(7)
+
R
≥ 8.8 k
f
5(9)
1.0 mA
2R
Error Amp compensation circuit for stabilizing any current mode topology except for boost and flyback
converters operating with continuous inductor current.
R
EA
2(3)
1(1)
From V
2.5V
O
+
1.0mA
R
p
2R
MCR
101
2N
3905
R
2(3)
i
5(9)
R
EA
2N
3903
C
C
R
f
f
p
R
d
1(1)
5(9)
The MCR101 SCR must be selected for a holding of < 0.5 mA @ T
be used in place of the SCR as shown. All resistors are 10 k.
. The simple two transistor circuit can
A(min)
Error Amp compensation circuit for stabilizing current mode boost and flyback
topologies operating with continuous inductor current.
13
MOTOROLA ANALOG IC DEVICE DATA
MOTOROLA [ MOTOROLA ]
