AIC3843
Open-Loop Laboratory Fixture
1k
8
V
REF
SHUTDOWN
1
COMP
330O
3
I
SENSE
500
SHUTDOWN
TO CURRENT SENSE
RESISTOR
Fig. 6-1
Fig. 6-2
Shutdown of the AIC3843 can be accomplished by two methods; either raise pin 3 above 1V or pull pin 1 below a voltage two-diode
drops above ground. Either method causes the output of the PWM comparator to be high (refer to block diagram). The PWM latch
is reset dominant so that the output will remain low until the next clock cycle after the shutdown condition at pin 1 and/or 3 is
removed. In one example, an externally latched shutdown may be accomplished by adding an SCR, which will be reset by cycling
Vcc below the lower UVLO threshold. At this point the reference turns off, allowing the SCR to reset.
Offline Flyback Regulator
R1
5
Ω
1W
117 VAC
L1
D6
VARO
VM68
C1
250
µ
F
250V
10µH
R
12
R2
56K
2W
2W
4.7K
D4
1N3613
1N3612
C9
3300pF
Np
T1
USD945
N5
C10
4700
µF
10V
C11
4700
µF
10V
+
5V
COM
D7
UFS1002
+12V
N12
16V
600V
R4
4.7k
R3
20k
7
2
R5 150k
1
AIC3843
C14 100pF
8
4 5
6
3
C2
D2
100
µ
F C3
25V
22µF
R9
68
Ω
3W
1N3613
D4
C12
2200
µ
F
±12V COM
C13
C4
25V
47
µ
F
Nc
N12
D8
2200
µ
F
16V
UES1002
-12V
R7
22Ω
R8
R13
10K
Q1
UFN833
R10
0.55
Ω
1W
16V
C5
0.01
µ
F
R6
10k
C6
C8
680pF
R11
2.7k
2W
0.0022
µ
F
USD1120
1k
C7
470pF
D5
1N3613
Power Supply Specifications
1. Input Voltage
2. Line Isolation
95VAC to 130VA
(50Hz/60Hz)
3750V
5. Output Voltage:
A. +5V, ±5%; 1A to 4A load
Ripple voltage: 50mV P-P Max
B. +12V, ±3%; 0.1A to 0.3A load
Ripple voltage: 100mV P-P Max
C. -12V, ±3%; 0.1A to 0.3A load
Ripple voltage: 100mV P-P Max
3. Switching Frequency
40kHz
4. Efficiency @ Full Load 70%
Fig. 7
7
AIC [ ANALOG INTERGRATIONS CORPORATION ]
