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PDF AIC3843 Data sheet ( Hoja de datos )
| Número de pieza | AIC3843 | |
| Descripción | Current-Mode PWM Controller | |
| Fabricantes | Analog Integrations | |
| Logotipo |  |
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AIC3843
Current-Mode PWM Controller
FEATURES
Low Start-Up Current (300µA Typical)
Internal Precision Reference.
500KHz Current-Mode Operation.
Pulse-by-Pulse Current Limiting.
Automatic Feed-Forward Compensation.
Optimized for Off-line and DC/DC Converters.
Under-voltage Lockout with Hysteresis.
Double Pulse Suppression.
High Current Totem Pole Output.
APPLICATIONS
AC/DC Off-line Converter.
DC/DC Off-line Converter.
DESCRIPTION
The AIC3843 control IC provides the features
that are necessary to implement off-line or
DC/DC Converter fixed-frequency current-mode
schemes with a minimum number of external
components. This integrated circuits features
an under-voltage lockout (UVLO) with approxi-
mately 300µA start-up current, a precision
reference trimmed for accuracy at the error
amplifier input, high gain error amplifier, current
sensing comparator, logic to insure latched
operation, and a totem-pole output stage
designed to source or sink high peak current.
The output stage, suitable for driving the N-
channel MOSFETs, is low in the off state.
TYPICAL APPLICATION CIRCUIT
2 VFB
7
VCC
C2 +
R3 300pF C3
51K 1000P
FEEDBACK
SIGNAL
C5
0.1µF
R4
7.5K
C4
2.2nF
1 COMP
8 VREF
6
OUTPUT
GND 5
R1
10
4 RT/CT
ISENSE 3
AIC3843
C6
300P
C1
47µF
VCC
INDUCTOR
M1
R2
20K
R5
390
C7
1nF
RS
0.33
Current Mode PWM Control Circuit
www.DataSheet4U.com
Analog Integrations Corporation
Si-Soft Research Center
3A1, No.1, Li-Hsin Rd. I , Science Park , Hsinchu 300, Taiwan , R.O.C.
TEL: 886-3-5772500
FAX: 886-3-5772510 www.analog.com.tw
DS-3843G-01 120508
1
1 page  
AIC3843
ELECTRICAL CHARACTERISTICS (Continued)
PARAMETERS
Current Sense Section
Voltage Amplification
Current Sense Comparator
Threshold
Supply Voltage Rejection
Ratio
Input Bias Current
Delay Time to Output
CONDITIONS
See Note 4 and 5
COMP at 5V, See Note 4
VCC=12V to 25V, See Note 4
Output Section
High-Level Output Voltage
Low-Level Output Voltage
Rise Time
Fall Time
ISOURCE=20mA
ISOURCE =200mA
ISINK=20mA
ISINK=200mA
CL=1nF
CL=1nF
Under voltage Lockout Section
Start Threshold Voltage
Minimum Operating Voltage
after Start-Up
Pulse-Width-Modulator Section
Maximum Duty Cycle
Minimum Duty Cycle
Supply Voltage
Start-Up Current
Operating Supply Current
Limiting Voltage
VFB and ISENSE at 0V
ICC=25mA
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MIN. TYP. MAX. UNITS
2.85 3 3.15 V/V
0.9 1 1.1 V
70
-2 -10
150 300
dB
µA
nS
13 13.5
V
12 13.4
V
0.1 0.4
V
1.5 2.2
V
50 150 nS
50 150 nS
7.8 8.4 9.0
7.0 7.6 8.2
V
V
95 96 100 %
0%
0.3 0.5 mA
12 17 mA
30 34
V
5
5 Page 
AIC3843
Open-Loop Laboratory Fixture
1k 8
VREF
SHUTDOWN
1
COMP
330Ω
3
ISENSE
SHUTDOWN
500
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
5Ω
1W
117 VAC
VARO
VM68
C1
250µF
250V
R2
56K
2W
R4 R3
4.7k 20k
R5 150k
7
2
1
C5
0.01µF
AIC3843
C14 100pF
8
R6
6
10k
45
C6
0.0022µF
3
1N3612
D2
C2 100µF C3
25V 22µF
R9
68Ω
3W
USD1120
R7
22Ω R8
1k
C7
470pF
R12
2W
4.7K
D4
1N3613
C9
3300pF
1N3613
D4
C4
25V
47µF
Nc
Q1
UFN833
R10
R13 0.55Ω
10K 1W
L1
D6 10µH
T1 USD945
+5V
Np
600V
N5
C10
4700µF
10V
C11
4700µF
10V
COM
D7 UFS1002
N12
16V
C12
2200µF
+12V
±12V COM
N12 C13
D8 2200µF
UES1002
16V
-12V
16V C8
680pF
D5
1N3613
R11
2.7k
2W
Power Supply Specifications
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1. Input Voltage
95VAC to 130VA
(50Hz/60Hz)
2. Line Isolation
3750V
3. Switching Frequency 40kHz
4. Efficiency @ Full Load 70%
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
Fig. 7
11
11 Page | ||
| Páginas | Total 13 Páginas | |
| PDF Descargar | [ Datasheet AIC3843.PDF ] | |
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