AIC3843
Current-Mode PWM Controller
n
FEATURES
l
Low Start-Up Current (300µA Typical)
l
Internal Precision Reference.
l
500KHz Current-Mode Operation.
l
Pulse-by-Pulse Current Limiting.
l
Automatic Feed-Forward Compensation.
l
Optimized for Off-line and DC/DC Converters.
l
Under-voltage Lockout with Hysteresis.
l
Double Pulse Suppression.
l
High Current Totem Pole Output.
n
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.
n
APPLICATIONS
l
AC/DC Off-line Converter.
l
DC/DC Off-line Converter.
n
TYPICAL APPLICATION CIRCUIT
2
C2
R3
51K
FEEDBACK
SIGNAL
300pF
C3
1000P
6
OUTPUT
GND
5
VFB
7
VCC
+
R1
10
R2
20K
R5
C6
300P
390
C7
1nF
RS
0.33
C1
47
µ
F
VCC
INDUCTOR
M1
1
8
COMP
VREF
R4
7.5K
C5
0.1
µ
F
4
RT/CT
ISENSE
3
AIC3843
C4
2.2nF
Current Mode PWM Control Circuit
Analog Integrations Corporation
4F, 9 Industry E. 9th Rd, Science-Based Industrial Park, Hsinchu, Taiwan
TEL: 886-3-5772500
FAX: 886-3-5772510
www.analog.com.tw
DS-3843-00 012102
1
AIC3843
n
ORDERING INFORMATION
AIC3843CXXX
PACKING TYPE
TR: TAPE & REEL
TB: TUBE
PACKAGE TYPE
N: PLASTIC DIP
S: SMALL OUT
LINE
Example: AIC3843CSTR
à
in SO-8 Package & Taping & Reel Packing Type
(CN is not available in TR packing type.)
DIP-8
SO-8
TOP VIEW
COMP 1
VFB 2
ISENSE 3
RT/CT 4
8 VREF
7 VCC
6 OUTPUT
5 GND
PIN CONFIGURATION
n
ABSOLUTE MAXIMUM RATINGS
Supply Voltage (Low Impedance Source )
… ..........… … … … .............… … … … … … ........................
30V
Supply Voltage (I
CC
<30mA)
...................… ..… … … … .… … … ..… … ................… … … ..........
Self Limiting
Output Current
..............… … … … … … … … … ....… … … … ....................… … … .… … … .........… .........
±1A
Output Energy (Capacitive Load)
...................… ........… … … … … .… .........… … … .… ......................
5µJ
Analog Inputs (Pins 2, 3)
… .....… … … … … … … … ...… ......… … … … .................… … … ....
-0.3V to +6.3V
Error Amp Output Sink Current
......… ....… .… … ...… … … … ................… … … .… … … … ...............
10mA
Operation Temperature Range
......… ....… .… … ...… … … … .................… … … … ...............
-40°C~85°C
......… … … … … … … … … ....… … … … ..… … ...............
1W
.........… … .… ..… .....… … … … … … … .............
725mW
-65°C to +150°C
SOIC Package
Storage Temperature Range
Note 1:
Power Dissipation at TA
≤25°C
DIP Package
.....… … ...… … … … ...........................… … ......… … … …
Lead Temperature (Soldering, 10 seconds)
.....… … ...… … … … ..… … … … … .… … ....… … ...........
300°C
All voltages are with respect to Pin 5.
All currents are positive into the specified terminal.
n
TEST CIRCUIT
V
REF
RT
R5
4.7K
Q2
2N2222
COMP
Error Amp.
Adjust
R7
4.7K
R4
100K
VFB
R6
10K
ISENSE
Adjust R3
5K
ISENSE
RT/CT
AIC3843
GROUND
CT
VCC
OUTPUT
VREF
C2
0.1
µ
F
R1
1K
1W
C1
0.1
µ
F
A
S1
VCC
OUTPUT
GND
2
AIC3843
n
ELECTRICAL CHARACTERISTICS
{V
otherwise specified.}
PARAMETERS
CONDITIONS
CC
= 15V (see Note 2), -40°C
≦
T
A
≦85°C,
unless
MIN.
TYP.
MAX.
UNITS
Reference Section
Output Voltage
Line Regulation
Load Regulation
Temperature Coefficient of
Output Voltage
Output Noise Voltage
Output Voltage Long Term
Drift
Short Circuit Output Current
Oscillator Section
Oscillator Frequency (see
Note 3)
Frequency Change with
Supply Voltage
Frequency Change with
Temperature
Peak-to-Peak Amplitude at
RT/CT
Error Amplifier Section
Feedback Input Voltage
Input Bias Current
Open-Loop Voltage
Amplification
Gain-Bandwidth Product
Supply Voltage Rejection
Ratio
Output Sink Current
Output Source Current
High-Level Output Voltage
Low-Level Output Voltage
V
CC
=12V to 25V
V
FB
at 2.7V, COMP at 1.1V
V
FB
at 2.3V, COMP at 5V
V
FB
at 2.3V, R
L
=15KΩ to GND
V
FB
at 2.7V, R
L
=15Ω to VREF
V
O
=2V to 4V
65
0.7
60
2
-0.5
5
COMP at 2.5V
2.42
2.50
-0.3
90
1
70
10
-1
6.2
0.8
1.1
2.58
-2
V
µA
dB
MHz
dB
mA
mA
V
V
VCC=12V to 25V
47
52
0.2
57
1
KHz
%
f =10Hz to 10KHz
After 1000H at T
A
=25°C
-30
I
O
=1mA
V
CC
=12V to 25V
I
O
=1mA to 20mA
4.9
5
5
5
0.2
50
5
-85
25
-180
5.1
20
25
0.4
V
mV
mV
mV/°C
µV
mV
mA
TA=TLOW to THIGH
5
1.7
%
V
3
AIC3843
n
ELECTRICAL CHARACTERISTICS
(Continued)
PARAMETERS
Current Sense Section
Voltage Amplification
Current Sense Comparator
Threshold
Supply Voltage Rejection
Ratio
Input Bias Current
Delay Time to Output
Output Section
High-Level Output Voltage
I
SOURCE
=20mA
I
SOURCE
=200mA
Low-Level Output Voltage
Rise Time
Fall Time
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
V
FB
and I
SENSE
at 0V
I
CC
=25mA
30
0.3
12
34
0.5
17
mA
mA
V
95
96
100
0
%
%
7.8
7.0
8.4
7.6
9.0
8.2
V
V
I
SINK
=20mA
I
SINK
=200mA
C
L
=1nF
C
L
=1nF
13
12
13.5
13.4
0.1
1.5
50
50
0.4
2.2
150
150
V
V
V
V
nS
nS
See Note 3 and 4
COMP at 5V, See Note 3
2.85
0.9
3
1
3.15
1.1
V/V
V
CONDITIONS
MIN.
TYP.
MAX.
UNITS
V
CC
=12V to 25V, See Note 3
70
-2
150
-10
300
dB
µA
nS
Note: 2: Adjust VCC above the start threshold before setting it to 15V.
3. These parameters are measured at the trip point of the latch with VFB at 0V.
4. Voltage amplification is measured between ISENSE and COMP with the input changing from 0V to
0.8V.
4
AIC3843
Error AMP Configuration
2.50V
0.5mA
+
V
FB
Z
I
Z
F
2
COMP
1
-
Error Amp can Source or Sink up to 0.5mA
Fig. 1
Under-Voltage Lockout
I
CC
7
17mA
AIC3843
V
ON
V
OFF
8.4V
7.6V
Fig. 2-1
500µA
V
CC
Fig. 2-2
V
OFF
V
ON
During under-voltage lockout, the output driver is biased to sink minor amounts of
current. Pin 6 should be shunted to ground with a bleeder resistor to prevent
activating the power switch with extraneous leakage currents.
Current Sense Circuit
Error AMP
2R
R
I
S
COMP
R
R
S
1V
Current Sense
Comparator
C
Current Sense
GND
Peak Current (Is) is Determined By The Formula
I
SMAX
≈
1.0V
R
S
A small RC filter may be required to suppress switch transients.
Fig. 3
5
京公网安备 11010802033920号
EEWORLD
