MC34025, MC33025
V
CC
V
in
16
V
ref
4
Clock
5
R
T
C
T
Ramp
Error Amp Output
3
2
Noninverting Input
Inverting Input
1
8
Soft−Start
C
SS
Q
S
R
Error
Amp
+
9.0
mA
Oscillator
6
7
PWM
Comparator
1.25 V
4.2 V
Reference
Regulator
15
V
CC
UVLO
9.2 V
V
CC
13
V
C
14
Output B
Q
Q
11
Current
Limit
1.0 V
9
Current Limit/
Shutdown
Shutdown
1.4 V
Output A
12
Power Ground
V
ref
UVLO
R
Q
S
PWM Latch
T
Steering
Flip Flop
0.5 V
Soft−Start Latch
10
Ground
Figure 19. Representative Block Diagram
C
T
Clock
Soft−Start
Error Amp Output
Ramp
PWM
Comparator
Output A
Output B
Figure 20. Current Limit Operating Waveforms
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