UC3842A, UC3843A, UC2842A, UC2843A
V
CC
V
CC
7(12)
36V
+
−
V
C
V
ref
UVLO
T Q
1.0mA
S
2R
R
1.0V
Current Sense
Comparator
GND
5(9)
+
−
=
−
+
Q
R
PWM
Latch
7(11)
Output
6(10)
Power Ground
5(8)
Current Sense Input
3(5)
R
S
Q1
V
in
V
ref
8(14)
R
2.5V
R
T
R
3.6V
Oscillator
4(7)
C
T
+
−
Error
Amplifier
+
Internal
Bias
Reference
Regulator
+
+ −
−
+
V
CC
UVLO
−
Voltage Feedback
Input
2(3)
Output
Compensation
1(1)
Sink Only
Positive True Logic
Pin numbers in parenthesis are for the D suffix SOIC−14 package.
Figure 18. Representative Block Diagram
Capacitor C
T
Latch
‘‘Set’’ Input
Output/
Compensation
Current Sense
Input
Latch
‘‘Reset’’ Input
Output
Large R
T
/Small C
T
Small R
T
/Large C
T
Figure 19. Timing Diagram
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