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AIC2863
3A 23V Synchronous PWM/PSM Step-Down
Converter with High Light-load Efficiency
 FEATURES
 DESCRIPTION

3A Continuous Output Current

Wide 4.75V to 23V Operating Input Range
Ouput Adjustable from 0.925V to 12V
(VREF=0.925V Version)
Ouput Adjustable from 0.8V to 12V
(VREF=0.8V Version)
Up to 84% Efficiency for Heavy Load
(Vin=12V, Vout=3.3V, Iout=3.0A)
Up to 91% Efficiency for Moderate Load
(Vin=12V, Vout=3.3V, Iout=1.0A)
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Low Rds(on) Internal Switches: 100mΩ and
85mΩ
<3µA Supply Current in Shutdown Mode
340KHz/550KHz Frequency
Programmable Soft Start
Thermal Shutdown
Cycle by Cycle Over Current Protection
Under Voltage Lockout
Short Circuit Protection
Over Voltage Protection
The AIC2863 is a 3A synchronous-rectified Buck
converter with integrated low Rds(on) power
MOSFETs. The AIC2863, designed with a currentmode control scheme, can convert wide input voltage to the adjustable output voltage to provide excellent output voltage regulation. It is stable with
low ESR output ceramic capacitors.
For high efficiency over all load current range, the
AIC2863 is equipped with an automatic PSM/PWM
mode operation. At light load, the IC operates in the
PSM (Pulse Skipping Mode) to reduce switching
losses. At heavy load, the IC works in PWM mode
to provide high efficiency and excellent output voltage regulation.
The AIC2863 is also equipped with soft start and
whole protections (under-voltage, over-voltage,
over-temperature, short circuit and current-limit) into a single package.
This device, available in SOP-8 package, provides
a very compact system solution with minimal external components and PCB area.
 APPLICATIONS

Networking Systems such as Modems & Routers


Distributed Power Systems
Pre-Regulator for Linear Regulators

Set-top Box
 TYPICAL APPLICATIONS CIRCUIT
AIC2863
Typical Application Circuit
Analog Integrations Corporation
Si-Soft Research Center
DS-2863G-04 20121218
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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AIC2863

PIN CONFIGURATION
AIC2863-XXXXX XX
PIN CONFIGURATION
PACKING TYPE
TR: TAPE & REEL
TB: TUBE
PACKAGING TYPE
R8: SOP-8 Exposed Pad (Heat Sink)
G: GREEN PACKAGE
SOP-8 Exposed Pad (Heat Sink)
TOP VIEW
BS
1
8 SS
IN
2
7 EN
SW
3
6 COMP
GND 4
5 FB
Note:
The exposed pad must be connected with
GND pin
3: fs=340KHz
5: fs=550KHz
Default: VREF=0.925V
K: V REF =0.8V
Example:
AIC2863-3GR8TR
 VREF =0.925V, fs=340KHz with GREEN SOP-8
Exposed Pad (Heat Sink) Package and TAPE &
REEL Packing Type
AIC2863-K5GR8TR
 VREF =0.8V, fs=550KHz with GREEN SOP-8
Exposed Pad (Heat Sink) Package and TAPE &
REEL Packing Type

ABSOLUTE MAXIMUM RATINGS
Input Voltage (VIN) ............................................................................................................... -0.3V to 26V
SW pin Voltage (VSW) .................................................................................................... -1V to VIN +0.3V
BS Pin Voltage ......................................................................................................... VSW-0.3V toVSW+6V
EN Pin Voltage ...................................................................................................................... -0.3V to VIN
All Other Pins Voltage ........................................................................................................... -0.3V to 6V
Operating Ambient Temperature Range TA ......................................................................... -40ºC~85ºC
Operating Maximum Junction Temperature TJ ............................................................................. 150ºC
Storage Temperature Range TSTG ..................................................................................... -65ºC~150ºC
Lead Temperature (Soldering 10 Sec.) ........................................................................................ 260ºC
Thermal Resistance Junction to Case
SOP-8 Exposed Pad* ............................................ 15C/W
Thermal Resistance Junction to Ambient
SOP-8 Exposed Pad* ............................................ 60C/W
(Assume no Ambient Airflow)
Absolute Maximum Ratings are those values beyond which the life of a device may be impaired.
*The package is place on a two layers PCB with 2 ounces copper and 2 square inch, connected by 8 vias.
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AIC2863

ELECTRICAL CHARACTERISTICS
(VIN=12V, VEN =5V, TA=25C, unless otherwise specified.) (Note1)
PARAMETER
Supply Voltage Range
Under Voltage Lockout Threshold
UVLO Hysteresis
Shutdown Supply Current
SYMBOL
VIN Rising
MIN
4.75
3.7
VEN = 0V
IOUT = 0A, VFB = 1.0V
No Switching
Standby Current
Reference Voltage (Default Version)
(Note2)
Reference Voltage (K Version)
(Note2)
Feedback Over Voltage Threshold
EN Shutdown Threshold Voltage
EN Shutdown Hysteresis
High-Side Switch On-Resistance
Low-Side Switch On-Resistance
High-Side Switch Leakage Current
High-Side Switch Current Limit
Oscillation Frequency (3 Version)
(Note2)
Oscillation Frequency (5 Version)
(Note2)
Short Circuit Oscillation Frequency
Maximum Duty Cycle
Minimum On Time
Soft-Start Current
Soft-Start Period
Thermal Shutdown
CONDITIONS
TYP
4.05
210
0.3
MAX UNITS
23
V
4.5
V
mV
3
A
0.7
1.5
mA
VREF
0.90
0.925
0.95
V
VREF
0.778
0.8
0.822
V
VFB Rising
VEN Rising
1.1
VEN = 0V, VSW = 0V
Peak Current
4.0
123
1.5
220
100
85
0
5.8
fs
300
340
380
KHz
fs
485
550
615
KHz
RDS(ON)1
RDS(ON)2
VFB = 0V
DMAX
TON
VSS = 0V
VSS = 0.1F
Trip Point
110
90
220
6
15
160
2.2
10
%
V
mV
m
m
A
A
KHz
%
ns
A
ms
C
Note 1: Specifications are production tested at TA=25C. Specifications over the -40C to 85C operating temperature range are assured by design, characterization and correlation with Statistical
Quality Controls (SQC).
Note 2: Referring to the ordering information.
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AIC2863

TYPICAL PERFORMANCE CHARACTERISTICS
VIN
10V/Div
VOUT
2V/Div
VSW
10V/Div
IL
2A/Div
VIN=12V,VOUT=3.3V,IOUT=3A
Time(20ms/Div)
Fig. 1 Efficiency vs. Load Current
VIN
5V/Div
Fig. 2 Start-Up Waveform at VOUT=3.3V, IOUT=3A
VIN
5V/Div
VOUT
2V/Div
VOUT
2V/Div
VSW
10V/Div
VSW
10V/Div
IL
5A/Div
VIN=12V,VOUT=3.3V,IOUT=3A
IL
5A/Div
VIN=12V,VOUT=3.3V,IOUT=3A
Time(4ms/Div)
Time(4ms/Div)
Fig. 3 Start-Up Waveform at VOUT=3.3V, IOUT=3A
Fig. 4 Shutdown Waveform at VOUT=3.3V, IOUT=3A
VIN=12V,VOUT=3.3V,IOUT=0.5A~2.5A
VOUT AC
500mV/Div
VIN=12V,VOUT=3.3V,IOUT=1A~3A
VOUT AC
500mV/Div
IL
2A/Div
IL
2A/Div
Time(1ms/Div)
Fig. 5 Load Transient at VOUT=3.3V, IOUT=0.5A to 2.5A
Time(1ms/Div)
Fig. 6 Load Transient at VOUT=3.3V, IOUT=1A to 3A
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AIC2863
 TYPICAL PERFORMANCE CHARACTERISTICS (Continued)
VOUT AC
20mV/Div
VOUT AC
20mV/Div
VSW
5V/Div
VSW
5V/Div
IL
1A/Div
IL
2A/Div
VIN=12V,VOUT=3.3V,IOUT=1A
Time(2μs/Div)
Fig. 7 Stability Waveform at VOUT=3.3V, IOUT=1A
VIN=12V,VOUT=3.3V,IOUT=3A
Time(2μs/Div)
Fig. 8 Stability Waveform at VOUT=3.3V, IOUT=3A
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AIC2863

BLOCK DIAGRAM
Functional Block Diagram of AIC2863 (VREF=0.925V Version)
Functional Block Diagram of AIC2863 (VREF=0.8V Version)
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AIC2863

PIN DESCRIPTIONS
Pin 1: BS:
High Side Gate Drive Boost Input.
BS supplies the drive for the highside N-Channel MOSFET switch.
Connect a 100nF or greater
capaitor from SW to BS to power
the high-side switch.
Pin 2: IN:
Power Input. IN supplies the power to the IC, as well as the stepdown converter switches. Drive IN
with a 4.5V to 23V power source.
By pass IN to GND with a suitably
large capacitor to eliminate noise
on the input to the IC.
Pin 3: SW:
Power Switching Output. SW is
the switching node that supplies
power to the output. Connect the
output LC filter from switch to the
output load. Note that a capacitor
is required from SW to BS to
power the high-side switch.
Pin 4:GND:
Ground. Connect the exposed
pad on backside to Pin 4.
Pin 5: FB:
Feedback Input. FB senses the
output voltage to regulate that
voltage. Drive feedback with a
resistive voltage divider from the
output voltage.
Pin 6: COMP:
Compensation Node. COMP is
used to compensate the regulation control loop. Connect a series RC network form COMP to
GND to compensate the regulation control loop. In some cases,
an additional capacitor from
COMP to GND is required.
Pin 7: EN:
Enable Input. EN is a digital input
that turns the regulator on or off.
Drive EN high to turn on the regulator. Drive it low to turn it off.
For automatic strat-up, attach to
IN with a 100k pull up resistor.
Pin 8: SS:
Soft Star Control Input. SS controls the soft star period. Connect
a capacitor from SS to GND to
set the soft-star period. A 0.1F
capacitor sets the soft-star period
to 15ms.
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AIC2863

APPLICATION INFORMATIONS
Soft-Start
The AIC2863 provides the soft-start function. Initially,
The AIC2863 is a synchronous high voltage buck
the voltage at SS pin is 0V. Then an internal current
converter that can support the input voltage range from
source of 6A (typ.) charges an external soft-start ca-
4.75V to 23V and the output current can be up to 3A.
pacitor. During the soft-start period, the voltage at SS
pin will limit the feedback threshold voltage at FB pin.
Setting the Output Voltage
When the voltage at SS pin is higher than reference
The output voltage is set using a resistive voltage
voltage, the feedback threshold voltage at FB pin
divider connected from the output voltage to FB. The
reaches the desired value. The soft-start time can be
voltage divider divides the output voltage down to the
calculated in accordance with the following equation.
feedback voltage by the ratio:
VFB = VOUT
t SS  C5 
R2
R1 + R2
VREF
6A
The soft-start capacitor is discharged to GND when the
EN pin is connected to GND.
Thus the output voltage is:
VOUT
R1  R2
 VREF 
R2
For
example,
for
Optional Schottky Diode
A Schottky diode with low forward drop voltage and
a
3.3V
output
voltage
and
VREF=0.925V, R2 is 10kΩ, and R1 is 25.6kΩ.
fast reverse recovery is the ideal choice for better
efficiency. The forward drop voltage of a Schottky
diode will result in the conduction losses in the diode,
Inductor
and the diode capacitance (CT or CD) will cause the
The inductor selection depends on the current ripple of
switching losses. Therefore, it is necessary to consider
inductor, the input voltage and the output voltage.
both forward voltage drop and diode capacitance for
L
VOUT
fOSC  IL

V 
1  OUT 
VIN 

Accepting a large current ripple of inductor allows the
diode selection. In addition, the rating of selected
Schottky diode should be able to handle the input
voltage and the maximum peak diode current.
use of a smaller inductance. However, higher current
ripple of inductor can cause higher output ripple
Input Capacitor and Output Capacitor
voltage and large core loss. By setting an acceptable
To prevent the high input voltage ripple and noise
current ripple of inductor, a suitable inductance can be
resulted from high frequency switching, the use of low
obtained from above equation.
ESR ceramic capacitor for the maximum RMS current
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  IOUT max  

VOUT 
V
1  OUT 
2  fOSC  L 
VIN 
is recommended. The approximated RMS current of
the input capacitor can be calculated according to the
following equation.
2
ICINRMS  IOUT
(MAX ) 
VOUT VIN  VOUT 
2
VIN

IL2
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The selection of output capacitor depends on the
required output voltage ripple. The output voltage
ripple can be expressed as:
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AIC2863
ΔVOUT =
8 × f OSC
ΔI L
+ ESR
× (C3 // C4)
ΔI L
FZ1 =
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
choosing
the
input
The system may have another zero of importance, if
the output capacitor has a large capacitance and/or a
high ESR value. The zero, due to the ESR and capacitance of the output capacitor, is located at:
than that of ceramic capacitor.
When
1
2π × Cc × Rc
and
output
ceramic
FESR =
capacitors, X5R and X7R types are recommended
1
2π × (C3 // C4) × RESR
because they retain their capacitance over wider
In this case, a third pole set by the compensation ca-
ranges of voltage and temperature than other types.
pacitor, C7 and the compensation resistor, Rc is used
to compensate the effect of the ESR zero on the loop
Loop Compensation
gain. This pole is located at:
FP 2 =
1
2π × C7 × Rc
※ The values of the compensation components are
given in the AIC2863 demo board user manual.
Layout Consideration
In order to avoid the poor output voltage ripple and low
efficiency caused by instability, AIC2863 requires a
proper external compensation network to compensate
its feedback loop. In this external compensation
network, the compensation resistor, RC, and the
compensation capacitor, CC, are used to set the highfrequency integrator gain and the integrator zero. C7 is
used to cancel the zero caused by the output capacitor
and it’s ESR. While using the ceramic capacitor as the
output capacitor, C7 can be omitted due to the small
ESR.
The system has one pole of importance, due to the
output capacitor, C3//C4 and the load resistor. This
poles is located at:
1
FP1 =
2π × (C3 // C4) × RLOAD
The system has one zero of importance, due to the
compensation capacitor, Cc and the compensation
resistor, Rc. This zero is located at:
In order to ensure a proper operation of AIC2863, 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 power switch, the Schottky diode 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. In order to prevent the effect from noise, the IC’s
GND pin should be placed close to the ground of
the input bypass capacitor.
6. The FB pin should be connected to the feedback
resistors directly and the route should be away
from the noise sources.
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AIC2863

PHYSICAL DIMENSIONS
 SOP-8 Exposed Pad (Heat Sink)
D
D1
EXPOSED THERMAL PAD(Heat Sink)
(BOTTOM CENTER OF PACKAGE)
h X 45°
A
SEE VIEW B
A
e
A
H
E
E1
WITH PLATING
0.25
C
A1
B
GAUGE PLANE
SEATING PLANE

L
VIEW B
BASE METAL
SECTION A-A
Note : 1. Refer to JEDEC MS-012E.
2. Dimension "D" does not include mold flash, protrusions
or gate burrs. Mold flash, protrusion or gate burrs shall not
exceed 6 mil per side .
3. Dimension "E" does not include inter-lead flash or protrusions.
4. Controlling dimension is millimeter, converted inch
dimensions are not necessarily exact.
S
Y
M
B
O
L
SOP-8 Exposed Pad(Heat Sink)
MILLIMETERS
MIN.
MAX.
A
1.35
1.75
A1
0.00
0.15
B
0.31
0.51
C
0.17
0.25
D
4.80
5.00
D1
1.50
3.50
E
3.80
4.00
E1
1.0
2.55
e
1.27 BSC
H
5.80
6.20
h
0.25
0.50
L
0.40
1.27
θ
0°
8°
Note:
Information provided by AIC is believed to be accurate and reliable. However, we cannot assume responsibility for use of any circuitry other
than circuitry entirely embodied in an AIC product; nor for any infringement of patents or other rights of third parties that may result from its use.
We reserve the right to change the circuitry and specifications without notice.
Life Support Policy: AIC does not authorize any AIC product for use in life support devices and/or systems. Life support devices or systems are
devices or systems which, (I) are intended for surgical implant into the body or (ii) support or sustain life, and whose failure to perform, when
properly used in accordance with instructions for use provided in the labeling, can be reasonably expected to result in a significant injury to the
user.
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