UC3844B, UC3845B, UC2844B, UC2845B
V
in
V
CC
7(12)
Isolation
Boundary
5.0V Ref
+
−
V
Waveforms
+
GS
+
0
−
+
−
7(11)
Q1
0
−
50% DC
25% DC
T
6(10)
5(8)
S
R
V
− 1.4
Q
(Pinꢁ1)
N
S
p
ǒ Ǔ
I
=
pk
N
3 R
S
R
3(5)
Comp/Latch
C
R
N
S
S
N
P
Figure 27. Isolated MOSFET Drive
8(14)
R
Bias
R
Osc
4(7)
+
1.0 mA
2R
R
2(3)
1(1)
EA
MCR
101
2N
3905
5(9)
2N
3903
The MCR101 SCR must be selected for a holding of < 0.5 mA @ T
. The
A(min)
simple two transistor circuit can be used in place of the SCR as shown. All
resistors are 10 k.
Figure 28. Latched Shutdown
2.5V
2.5V
From V
From V
O
O
+
+
1.0mA
1.0mA
2R
2R
R
R
p
i
R
2(3)
2(3)
i
R
R
C
EA
C
EA
C
f
R
f
R
p
f
f
R
R
d
d
1(1)
1(1)
R ≥ 8.8k
f
5(9)
5(9)
Error Amp compensation circuit for stabilizing any current mode topology except
for boost and flyback converters operating with continuous inductor current.
Error Amp compensation circuit for stabilizing current mode boost
and flyback topologies operating with continuous inductor current.
Figure 29. Error Amplifier Compensation
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