MC34067, MC33067
V
CC
15
50k
50k
7.0k
7.0k
V
ref
Enable /
UVLO Adjust
5.1 V
Reference
V
ref
9
5
V
UVLO
CC
8.0 V
V
ref
UVLO
V
ref
4.2/4.0 V
D1
OSC Charge
OSC RC
Q1
14
13
Q2
1
2
Output A
Steering
Flip−Flop
Oscillator
R
Power
Ground
OSC
Q
T
C
OSC
I
OSC
4.9V/3.6 V
Q
R
One−Shot RC
16
One−Shot
3.1V
C
R
T
Oscillator
Control Current
Output B
T
12
10
4.9 V/3.6 V
3
VFO
I
OSC
R
Fault Comparator
R
S
Q
Fault Input
Error Amp Output
6
8
1.0 V
Fault
Latch
Noninverting Input
Inverting Input
Error Amp
Clamp
9.0 mA
7
Error Amp
Soft−Start
11
4
Ground
Figure 14. MC34067 Representative Block Diagram
5.1 V
C
OSC
3. 6 V
5.1 V
3.6 V
One−Shot
Output A
Output B
t
t
t
t
t
t
OS
OS
OS
OS
OS
OS
High State Error Amp output, minimum I
current
Low State Error Amp output, maximum I
current
OSC
OSC
occurring at minimum input voltage, maximum load.
occurring at maximum input voltage, minimum load.
Figure 15. Timing Diagram
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ONSEMI [ ONSEMI ]
