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PDF AIC1741 Data sheet ( Hoja de datos )
| Número de pieza | AIC1741 | |
| Descripción | LOW DROPOUT ADJUSTABLE REGULATOR | |
| Fabricantes | Analog Intergrations Corporation | |
| Logotipo |  |
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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.
APPLICATIONS
Voltage Regulator for Pentium® CPUs.
Wireless Communication System.
5V to 3.3V Regulator for VGA Cards.
Battery Powered Systems.
TYPICAL APPLICATION CIRCUIT
AIC1741
LOW DROPOUT ADJUSTABLE REGULATOR
SPEC NO: DS-1741-00
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.
VIN
5V
Q1
TIP31C
VOUT
3.3V/3 A
C3 +
10µF
R3
2K
1 VOUT
2 NC
+
R1 C2
3 GND
390 33µF 4 NC
8
VIN
FB 7
FLAG 6
NC 5
AIC1741
R2
1.2K
+ C1
10µF
5V to 3.3V Regulator for VGA Cards.
ORDERING INFORMATION
AIC1741 XX
PACKAGE TYPE
N: PLASTIC DIP
S: SMALL OUTLINE
ORDER NUMBER
AIC1741CN
(PLASTIC DIP)
TEMPERATURE RANGE
C: 0°C~+70°C
AIC1741CS
(PLASTIC SO)
PIN CONFIGURATION
TOP VIEW
VOUT 1
NC 2
GND 3
NC 4
8 VIN
7 FB
6 FLAG
5 NC
Pentium® is a registered trademark of Intel Corporation
ANALOG INTEGRATIONS CORPORATION
www.analog.com.tw
4F, 9 Industry E. 9th Road, Science-based Industrial Park , Hsinchu, Taiwan, R.O.C. TEL: (8863)577-2500 FAX:(8863)577-2510
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1 page  
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.
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:
VOUT=VREF(1+R1/R2)+IFBR1
where VREF is the nominal 1.235V reference voltage
and IFB is the feedback pin bias current, nominally
-20nA. For better accuracy, the recommended
maximum value of R2 is 100KΩ.
A 1µF (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 5Ω. 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 µF or greater
capacitor should be used.
AIC1741
LOW DROPOUT ADJUSTABLE REGULATOR
SPEC NO: DS-1741-00
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 3.3µF 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 390Ω
resistor and 1µF capacitor are needed between
VOUT pin and ground for stability. The minimum
dropout voltage between input to output is VBEQ1+VDS
of AIC1741 output PMOSFET, typical 1V @ 3A
output current.
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.
A 0.1µF 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
www.analog.com.tw
4F, 9 Industry E. 9th Road, Science-based Industrial Park , Hsinchu, Taiwan, R.O.C. TEL: (8863)577-2500 FAX:(8863)577-2510
5
5 Page | ||
| Páginas | Total 6 Páginas | |
| PDF Descargar | [ Datasheet AIC1741.PDF ] | |
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