AIC1741
LOW DROPOUT ADJUSTABLE REGULATOR
SPEC NO: DS-1741-00
FEATURES
1% Accuracy 1.235V Voltage Reference.
Fast Transient Response.
Low Ground Current at 55µA.
Wide Output Current Range, 10µA~80mA.
Output Programmable from 1.235V~11V.
Low Temperature Coefficiency.
Error Flag Warns of Output Dropout.
DESCRIPTION
The AIC1741 is a low power precision adjustable
regulator with 80mA output capability. The device
can be used as a secondary regular to provide
feedback in a switching power supply.
The AIC1741 circuitry includes an internal wide
band amplifier, a precision bandgap reference,
and a PMOS output transistor. The feedback
input can be connected to an external resistor
divider to program the sensed output voltage.
The
VOUT
pin
provides
loop
frequency
compensation when used as a part of a larger
servo system.
Although the device works as a stand-alone
regulator, it can also drive an NPN power
transistor to construct a high current low dropout
regulator, with only very minor current loss to
ground.
APPLICATIONS
Voltage Regulator for Pentium
®
CPUs.
Wireless Communication System.
5V to 3.3V Regulator for VGA Cards.
Battery Powered Systems.
TYPICAL APPLICATION CIRCUIT
V
IN
5V
Q1
TIP31C
V
OUT
3.3V/3 A
C3
10µF
+
R3
2K
R1
390
+
C2
33µF
1
VOUT
2
NC
3
GND
4
VIN
8
+
FB
7
FLAG
6
NC
5
C1
10µF
NC
AIC1741
R2
1.2K
5V to 3.3V Regulator for VGA Cards.
ORDERING INFORMATION
AIC1741 XX
PACKAGE TYPE
N: PLASTIC DIP
S: SMALL OUTLINE
TEMPERATURE RANGE
C: 0°C~+70°C
ORDER NUMBER
AIC1741CN
(PLASTIC DIP)
PIN CONFIGURATION
TOP VIEW
VOUT
NC
1
2
3
4
8
7
6
5
VIN
FB
FLAG
NC
AIC1741CS
(PLASTIC SO)
®
GND
NC
Pentium
ANALOG INTEGRATIONS CORPORATION
4F, 9 Industry E. 9th Road, Science-based Industrial Park , Hsinchu, Taiwan, R.O.C.
is a registered trademark of Intel Corporation
www.analog.com.tw
TEL: (8863)577-2500 FAX:(8863)577-2510
1
AIC1741
LOW DROPOUT ADJUSTABLE REGULATOR
SPEC NO: DS-1741-00
ABSOLUTE MAXIMUM RATINGS
Input Supply Voltage
Feedback Input Voltage
Shutdown Input Voltage
Error Comparator Output
................……………...................................................... -
0.3~12V
.............……………...................................................... -
0.3~12V
...........……………....................................................... -
0.3~12V
..........………….......................................................... -
0.3~12V
………..........................................
-40
°
C~125
°
C
...............………….........................................
-65
°
C~150
°
C
Operating Junction Temperature Range
Storage Temperature Range
TEST CIRCUIT
8
V
IN
+
C
IN
1µF
1mA
7
VIN
FB
VOUT
NC
1
2
V
OUT
3.3V
C
OUT
10µF
R1
2K
R2
1.2K
6 FLAG
5
NC
AIC1741
GND 3
NC
4
ELECTRICAL CHARACTERISTICS
(Ta=25°C, C
IN
=1µF, C
OUT
=
10µF, unless otherwise
°
µ
µ
specified. Test conditions are referred to TEST CIRCUIT.)
PARAMETER
Output Voltage
Output Voltage Temperature
Coefficiency
Line Regulation
Load Regulation
(Note 2)
TEST CONDITIONS
V
IN
=3.6~12V, No Load, V
OUT
=3.3V
(Note 1)
V
IN
=3.6~12V, I
L
=1mA, V
OUT
=3.3V
V
IN
=7V, I
L
=0.1~80mA, V
OUT
=3.3V
I
L
=0.1mA
I
L
=80mA, V
OUT
=3.3V
V
IN
=4~12V, I
O
=0.1mA~I
MAX
V
IN
=7V
I
OL
=1mA, V
IN
=2.9V
MIN.
3.267
TYP.
3.3
50
3
4
0.2
200
55
MAX.
3.333
150
10
10
10
300
80
1
UNIT
V
PPM/
°
C
mV
mV
mV
µ
A
µ
A
Dropout Voltage
(Note 3)
Ground Current
Flag Pin Off Leakage Current
Flag Pin Pull Low Voltage
100
300
mV
Flag Pin Upper Threshold
40
60
mV
Voltage
Flag Pin Lower Threshold
68
88
mV
Voltage
Note 1:
Guaranteed by design.
Note 2:
Regulation is measured at constant junction temperature, using pulse testing with a low ON time.
Note 3:
Dropout voltage is defined as the input to output differential at which the output voltage drops 100mV
below the value measured with a 1V differential.
ANALOG INTEGRATIONS CORPORATION
4F, 9 Industry E. 9th Road, Science-based Industrial Park , Hsinchu, Taiwan, R.O.C.
www.analog.com.tw
TEL: (8863)577-2500 FAX:(8863)577-2510
2
AIC1741
LOW DROPOUT ADJUSTABLE REGULATOR
SPEC NO: DS-1741-00
TYPICAL PERFORMANCE CHARACTERISTICS
Reference Voltage vs. Temperature
1.28
60
Ground Current vs. Input Voltage
1.26
50
Reference Voltage (V)
V
REF
=1.244V
1.24
Ground Current (µA)
125
40
V
REF
=1.225V
1.22
30
V
REF
=1.225V
1.2
20
10
1.18
-50
-25
0
25
50
75
100
0
0
2
4
6
8
Temperature (°C)
Input Voltage (V)
10
12
Ground Current vs. Temperature
60
200
Dropout Voltage vs. Load Current
58
V
OUT
=3.3V
Dropout Voltage (mV)
I
L
=80mA
150
Ground Current (µA)
56
100
54
I
L
=0.1mA
52
50
50
-50
-25
0
25
50
75
100
125
0
0
20
40
60
80
100
Temperature(°C)
Load Current (mA)
Dropout Voltage vs Temperature
300
40
Bias Current vs. Temperature
250
V
OUT
=3.3V
I
L
=80mA
Bias Current (nA)
I
L
=0.1mA
30
Dropout Voltage(mV)
200
150
100
20
50
0
-50
-25
0
25
50
75
100
125
10
-50
-25
0
25
50
75
100
125
Temperature(°C)
Temperature (°C)
ANALOG INTEGRATIONS CORPORATION
4F, 9 Industry E. 9th Road, Science-based Industrial Park , Hsinchu, Taiwan, R.O.C.
www.analog.com.tw
TEL: (8863)577-2500 FAX:(8863)577-2510
3
AIC1741
LOW DROPOUT ADJUSTABLE REGULATOR
SPEC NO: DS-1741-00
TYPICAL PERFORMANCE CHARACTERISTICS
Minimum Operating Voltage vs Temperature
2.8
(CONTINUED)
Minimum Operating Voltage (V)
2.7
2.6
2.5
2.4
2.3
2.2
-50
-25
0
Temperature (°C)
25
50
75
100
125
BLOCK DIAGRAM
8
VIN
7
FB
+
-
1
VOUT
66mV
+
6
FLAG
3
GND
-
1.235V, Reference
PIN DESCRIPTIONS
PIN 1: VOUT - Output pin.
PIN 2: NC
PIN 3: GND
PIN 4: NC
PIN 5: NC
-
- Power GND.
-
-
PIN 6: FLAG - Open drain output of error flag
warns.
PIN 7: FB
PIN 8: VIN
- Error amplifier positive feedback
(see Block Diagram)
- Power supply input.
ANALOG INTEGRATIONS CORPORATION
4F, 9 Industry E. 9th Road, Science-based Industrial Park , Hsinchu, Taiwan, R.O.C.
www.analog.com.tw
TEL: (8863)577-2500 FAX:(8863)577-2510
4
AIC1741
LOW DROPOUT ADJUSTABLE REGULATOR
SPEC NO: DS-1741-00
APPLICATION INFORMATIONS
The AIC1741 has two major applications, one as a
low dropout linear regulator and another an error
amplifier for a switching power supply to provide
precision feedback control.
nearby noise sources can also upset the output. This
may especially be a problem when using high value
external resistors to set the output voltage. Adding a
100pF capacitor between output and feedback and
increasing the output capacitor to at least 3.3
µ
F will
cure this problem.
The AIC1741 can drive low cost NPN bipolar
transistor to deliver more output current. Typical
application circuit is an example of 5V to 3.3V linear
regulator for VGA cards power supply. A 390
Ω
resistor and 1
µ
F capacitor are needed between
VOUT pin and ground for stability. The minimum
dropout voltage between input to output is V
BEQ1
+V
DS
of AIC1741 output PMOSFET, typical 1V @ 3A
output current.
Use as a Linear Regulator
When AIC1741 is connected as a low dropout linear
regulator, two external divider resistors are needed to
set the output voltage (see Test Circuit). The output
voltage can be calculated from the following formula:
V
OUT
=V
REF
(1+R1/R2)+I
FB
R1
where V
REF
is the nominal 1.235V reference voltage
and I
FB
is the feedback pin bias current, nominally
-20nA. For better accuracy, the recommended
maximum value of R2 is 100K
Ω
.
A 1
µ
F (or greater) capacitor is required between the
AIC1741 output and ground for stability. Without this
capacitor the part will oscillate. Even though most
types of capacitor may work, if Aluminum electrolytic
type is used, the equivalent series resistance (ESR)
should be held to 5
Ω
. or less. Many Aluminum
electrolytics have electrolytes that freeze at about
-30
°
C, so solid tantalums are recommended for
operation below -25
°
C. The value of this capacitor
may be increased without limit.
The output capacitance required for stability varies
with output voltage (smaller for higher output voltage)
and output current (smaller for lower output currents).
At the worst-case situation of a 80mA load at 1.235V
output (output shorted to FB pin) a 3.3
µ
F or greater
capacitor should be used.
A 0.1
µ
F capacitor should be placed from the
AIC1741 input to ground if the lead inductance
between the input and power source exceeds 500nH
(approximately 10 inches of trace). Noise injection
into the feedback terminal of the AIC1741 from
ANALOG INTEGRATIONS CORPORATION
4F, 9 Industry E. 9th Road, Science-based Industrial Park , Hsinchu, Taiwan, R.O.C.
Use as an Error Amplifier
Fig. 1 shows a popular application for the AIC1741 in
switching power supply. The output voltage is sensed
between FB pin and GND pin of the AIC1741 through
the divider resistor. The VIN pin servos to control the
duty cycle of the pulse width modulator to stabilize
the output voltage at the set voltage. The FB pin and
VIN pin are in same phase while the FB pin and
VOUT pin are in opposite phases. Connecting a
capacitor from VOUT pin to FB pin provides
frequency compensation for the control loop. The
AIC1741 provides output voltage remote sensing to
improve precision and regulation specifications of the
output of the switching power supply.
www.analog.com.tw
TEL: (8863)577-2500 FAX:(8863)577-2510
5
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