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PDF AIC2354 Datasheet ( Hoja de datos )

Número de pieza AIC2354
Descripción PWM/PSM Step-Down DC/DC Converter
Fabricantes Analog Intergrations Corporation 
Logotipo Analog Intergrations Corporation Logotipo

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AIC2354 Hoja de datos, Descripción, Manual
AIC2354
1A Synchronous PWM/PSM Step-Down
DC/DC Converter
FEATURES
2.5V to 5.5V Input Voltage Range
1.0A Guaranteed Output Current
Up to 95% Efficiency
Low RDS(ON) Internal Switche: 280m
No Schottky Diode Required
100% Duty Cycle in Low Dropout Operation
Operating Frequency: 1.5MHz
Accurate Reference 0.6V Provides Low
Output Voltages
APPLICATIONS
LCD TV
Multi-function Peripheral
Cellular Phones
CPU I/O Supplies
Cordless Phones
PDAs and Handy-Terminals
Battery-Operated Devices (1 Li-Ion or 3
NiMH/ NiCd)
APPLICATIONS CIRCUIT
DESCRIPTION
The AIC2354 is a low-noise, pulse-width-
modulated (PWM), DC-DC step-down converter.
The device is available in an adjustable version
and fixed output voltages of 1.0V, 1.2V, 1.5V,
1.8V, and 3.3V.
The device features an internal synchronous
rectifier for high efficiency; it requires no external
Schottky diode. The AIC2354 is ideally suited for
Li-Ion battery applications. PWM/PSM mode
extends battery life by switching to a pulse-
skipping-modulated mode during light loads.
Shutdown mode places the device in standby,
reducing supply current to under 1µA.
Other features of the AIC2354 include high
efficiency, low dropout voltage, short circuit
protection, over temperature protection, and
over voltage protection. It is available in a small
5 pins SOT-23 and a 6 pins DFN package.
Fig. 1 Fixed Step-Down DC/DC Converter
Analog Integrations Corporation
Si-Soft Research Center
DS-2354G-02 20111101
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
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AIC2354 pdf
AIC2354
ELECTRICAL CHARACTERISTICS
(TA=25C, VIN=3.6V unless otherwise specified.) (Note 1)
PARAMETER
CONDITIONS
SYMBOL MIN
TYP
MAX
UNITS
Input Voltage Range
VIN 2.5
5.5 V
Output Adjustment Range
VOUT
0.6V
VIN-0.3V
V
Reference Voltage
FB Input Current
P-Channel On-Resistance
N-Channel On-Resistance
LX Leakage Current
VFB = VIN
IOUT = 0.2A
IOUT = 0.2A
VLX=0V or VLX=3.6V
VREF 0.588 0.6 0.612
IFB -50
50
PRDS(ON)
280 390
NRDS(ON)
250 390
-1 1
V
nA
m
m
A
Peak Inductor Current
Quiescent Current
Shutdown Supply Current
EN High-Level Input Voltage
VIN = 5V
IOUT = 0mA,
VFB=VREF + 5%
EN = GND
VIN=2.5V to 5.5V
IPK
IQ
ISHDN
VEN_H
1.3 1.6
65
0.1
1.5
85
1
A
A
A
V
EN Low-Level Input Voltage
VIN=2.5V to 5.5V
VEN_L
0.4 V
Oscillator Frequency
fOSC
1.2 1.5
1.8
MHz
Maximum Duty Cycle
Thermal Shutdown Temperature
DMAX
100
150
%
°C
Thermal Shutdown Hysteresis
25 °C
Note 1: Specifications are production tested at TA=25C. Specifications over the -40C to 85C operating tem-
perature range are assured by design, characterization and correlation with Statistical Quality Con-
trols (SQC).
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AIC2354 arduino
AIC2354
switching cycle is begun. While the input voltage
approaches the output voltage, the switching
frequency decreases gradually to smoothly transit to
100% duty cycle operation.
If input voltage is very close to output voltage, the
switching mode goes from pure PWM mode to 100%
duty cycle operation. During this transient state
mentioned above, large output ripple voltage may
appear on output terminal.
Components Selection
Inductor
The inductor selection depends on the current ripple of
inductor, the input voltage and the output voltage.
L
VOUT
fOSC  IL
1
VOUT
VIN

Accepting a large current ripple of inductor allows the
use of a smaller inductance. However, higher current
ripple of inductor can cause higher output ripple
voltage and large core loss. By setting an acceptable
current ripple of inductor, a suitable inductance can be
obtained from above equation.
In addition, it is important to ensure the inductor
saturation current exceeds the peak value of inductor
current in application to prevent core saturation. The
peak value of inductor current can be calculated
according to the following equation.
IPEAK
IOUTmax
VOUT
2 fOSC
L 1
VOUT
VIN

Input Capacitor and Output Capacitor
To prevent the high input voltage ripple and noise
resulted from high frequency switching, the use of low
ESR ceramic capacitor for the maximum RMS current
is recommended. The approximated RMS current of
the input capacitor can be calculated according to the
following equation.
 ICINRMS
IO2 UT(MAX)
VOUT
VIN VOUT
VI2N
IL2
12
The selection of output capacitor depends on the
required output voltage ripple. The output voltage
ripple can be expressed as:
VOUT
IL
8 fOSC COUT
ESR  IL
For lower output voltage ripple, the use of low ESR
ceramic capacitor is recommended. The tantalum
capacitor can also be used well, but its ERS is larger
than that of ceramic capacitor.
When choosing the input and output ceramic
capacitors, X5R and X7R types are recommended
because they retain their capacitance over wider
ranges of voltage and temperature than other types.
Output Voltage Programming (AIC2354 Adjustable
Version Only)
By connecting a resistive divider R1 and R2, the output
voltage of AIC2354 step-down converter can be set.
VOUT can be calculated as:
VOUT
0.6  1
R1
R2

The resistive divider should sit as close to VFB pin as
possible.
Layout Consideration
In order to ensure a proper operation of AIC2354, the
following points should be managed comprehensively.
1. The input capacitor and VIN should be placed as
close as possible to each other to reduce the input
voltage ripple and noise.
2. The output loop, which is consisted of the inductor,
the internal main power switch, the internal syn-
chronous power switch and the output capacitor,
should be kept as small as possible.
3. The routes with large current should be kept short
and wide.
4. Logically the large current on the converter should
flow at the same direction.
5. The VFB pin should be connected to the feedback
resistors directly and the route should be away
from the noise sources.
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