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AIC2862
2A 23V Synchronous PWM/PSM Step-Down
Converter with High Light-load Efficiency
 FEATURES
 DESCRIPTION

2A Continuous Output Current

Wide 4.75V to 23V Operating Input Range
Ouput Adjustable from 0.925V to 12V
Up to 89% Efficiency for Heavy Load
(Vin=12V, Vout=3.3V, Iout=2.0A)
Up to 92% Efficiency for Moderate Load
(Vin=12V, Vout=3.3V, Iout=1.0A)
Up to 81% Efficiency for Light Load
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(Vin=12V, Vout=3.3V, Iout=20mA)
Low Rds(on) Internal Switches: 140mΩ and
120mΩ
<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
 APPLICATIONS

Networking Systems such as Modems &
Routers
Distributed Power Systems
Pre-Regulator for Linear Regulators

Set-top Box
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
The AIC2862 is a 2A synchronous-rectified Buck
converter with integrated low Rds(on) power
MOSFETs. The AIC2862, designed with a current-mode 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
AIC2862 is equipped with an automatic
PSM/PWM modeoperation. 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 AIC2862 is also equipped with softstart 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.
 TYPICAL APPLICATIONS CIRCUIT
Typical Application Circuit
Analog Integrations Corporation
Si-Soft Research Center
DS-2862G-02 20120807
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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AIC2862

PIN CONFIGURATION
AIC2862-XXXX XX
PIN CONFIGURATION
PACKING TYPE
TR: TAPE & REEL
TB: TUBE
SOP-8 Exposed Pad (Heat Sink)
TOP VIEW
PACKAGING TYPE
R8: SOP-8 Exposed Pad (Heat Sink)
G: GREEN PACKAGE
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
Example:
AIC2862-3GR8TR
 340KHz 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 to Vsw + 6V
EN Pin Voltage…………………………………………………………………………………….... - 0.3V to VIN
All Other Pins Voltage……………………………………………………………………………..… - 0.3V to 6V
Operating Ambient Temperature Range TA………...............................…….…..................... - 40C ~ 85C
Operating Maximum Junction Temperature TJ……….……………...………….………………........... 150C
Storage Temperature Range TSTG ......................................................................................... -65ºC~150ºC
Lead Temperature (Soldering 10 Sec.)…………………………………………………..……………… 260C
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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AIC2862

ELECTRICAL CHARACTERISTICS
VIN=12V, unless otherwise specified. Typical values are at TA=+25C
PARAMETER
Supply Voltage Range
Under Voltage Lockout Threshold
UVLO Hysteresis
Shutdown Supply Current
Standby Current (Switching)
Reference Voltage
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 fs=340KHz
Oscillation Frequency fs=550KHz
Short Circuit Oscillation Frequency
Maximum Duty Cycle
Minimum On Time
Soft-Start Current
Soft-Start Period
Thermal Shutdown
SYMBOL
CONDITIONS
VIN Rising
VEN = 0V
VEN = 3.0V; SW = NC
VREF
VFB Rising
VEN Rising
RDS(ON)1
RDS(ON)2
VEN = 0V, VSW = 0V
Peak Current
fs
fs
VFB = 0V
DMAX
TON
VSS = 0V
VSS = 0.1F
Trip Point
MIN
4.75
3.7
TYP
4.05
210
0.3
0.7
0.900 0.925
123
1.1
1.5
220
140
120
0
2.7
3.4
300
340
485
550
110
90
220
6
15
160
MAX UNITS
23
V
V
mV
3
A
1.5
mA
0.95
V
%
2.2
V
mV
m
m
10
A
A
380
KHz
615
KHz
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).
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AIC2862

TYPICAL PERFORMANCE CHARACTERISTICS
Fig. 1 Efficiency vs. Load Current at VIN = 12V
Fig. 2 Start-Up Waveform at VOUT=3.3V, IOUT=2A
Fig. 3 Start-Up Waveform at VOUT=3.3V, IOUT=2A
Fig. 4 Shutdown Waveform at VOUT=3.3V, IOUT=2A
Fig. 5 Shutdown Waveform at VOUT=3.3V, IOUT=2A
Fig. 6 Load Transient at VOUT=3.3V, IOUT=1A to 2A
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AIC2862

TYPICAL PERFORMANCE CHARACTERISTICS (Continued)
Fig. 7 Load Transient at VOUT=3.3V, IOUT=0.5A to 2A
Fig. 8 Stability Waveform at VOUT=3.3V, IOUT=1A
Fig. 9 Stability Waveform at VOUT=3.3V, IOUT=2A
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AIC2862

BLOCK DIAGRAM
Functional Block Diagram of AIC2862

PIN DESCRIPTIONS
Pin No.
Pin Name
1
BS
2
IN
3
SW
4
5
GND
FB
6
COMP
7
EN
8
SS
Pin Function
High Side Gate Drive Boost Input. BS supplies the drive for the high-side N-Channel
MOSFET switch. Connect a 10nF or greater capaitor from SW to BS to power the
high-side switch.
Power Input. IN supplies power to the IC, as well as the step-down converter switches.
By pass IN to GND with a suitabley large capacitor to eliminate noise on the input to the
IC.
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.
Ground. Connect the exposed pad on backside to Pin 4.
Feedback Input. FB senses the output voltage to regulate that voltage. Drive feedback
with a resistive voltage divider from the output voltage.
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.
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.
Soft Star Contol Input. SS controls the soft star period. Connect a capacitor from SS
to GND to set the soft-star period. To disable the soft-star feature, leave the SS pin
unconnected.
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AIC2862

APPLICATION INFORMATIONS
The AIC2862 is a synchronous high voltage buck
The AIC2862 provides the soft-start function. Initially,
converter that can support the input voltage range from
the voltage at SS pin is 0V. Then an internal current
4.75V to 23V and the output current can be up to 2A.
source of 6A (typ.) charges an external soft-start capacitor. During the soft-start period, the voltage at SS
Setting the Output Voltage
pin will limit the feedback threshold voltage at FB pin.
The output voltage is set using a resistive voltage
When the voltage at SS pin is higher than 0.925V, the
divider connected from the output voltage to FB. The
feedback threshold voltage at FB pin reaches the de-
voltage divider divides the output voltage down to the
sired value. The soft-start time can be calculated in
feedback voltage by the ratio:
accordance with the following equation.
VFB = VOUT
t SS = C5 ×
R2
R1 + R2
The soft-start capacitor is discharged to GND when the
Thus the output voltage is:
VOUT = 0.925 ×
0.925 V
6μA
R1 + R2
R2
EN pin is connected to GND.
Optional Schottky Diode
A Schottky diode with low forward drop voltage and
For example, for a 3.3V output voltage, R2 is 10kΩ,
fast reverse recovery is the ideal choice for better
and R1 is 26.1kΩ.
efficiency. The forward drop voltage of a Schottky
Inductor
diode will result in the conduction losses in the diode,
The inductor selection depends on the current ripple of
inductor, the input voltage, and the output voltage.
VOUT
L
fOSC  IL
 VOUT 

1 
V
IN 

and the diode capacitance (CT or CD) will cause the
switching losses. Therefore, it is necessary to consider
both forward voltage drop and diode capacitance for
diode selection. In addition, the rating of selected
Accepting a large current ripple of inductor allows the
Schottky diode should be able to handle the input
use of a smaller inductance. However, higher current
voltage and the maximum peak diode current.
ripple of inductor can cause higher output ripple
Input Capacitor and Output Capacitor
voltage and large core loss. By setting an acceptable
current ripple of inductor, a suitable inductance can be
obtained from above equation.
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
In addition, it is important to ensure the inductor
is recommended. The approximated RMS current of
saturation current exceeds the peak value of inductor
the input capacitor can be calculated according to the
current in application to prevent core saturation. The
following equation.
peak value of inductor current can be calculated
according to the following equation.
IPEAK  IOUT max  

VOUT 
V
1  OUT 
2  fOSC  L 
VIN 
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
Soft-Start
ripple can be expressed as:
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AIC2862
ΔVOUT =
ΔIL
8 × f OSC × C3
+ ESR
The system may have another zero of importance, if
ΔIL
the output capacitor has a large capacitance and/or a
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
high ESR value. The zero, due to the ESR and capacitance of the output capacitor, is located at:
FESR =
than that of ceramic capacitor.
When
choosing
the
input
and
output
ceramic
1
2π × C3 × RESR
In this case, a third pole set by the compensation ca-
capacitors, X5R and X7R types are recommended
pacitor, C7 and the compensation resistor, Rc is used
because they retain their capacitance over wider
to compensate the effect of the ESR zero on the loop
ranges of voltage and temperature than other types.
gain. This pole is located at:
Loop Compensation
FP 2 =
1
2π × C7 × Rc
※ The values of the compensation components are
given in the AIC2862 demo board user manual.
Layout Consideration
In order to ensure a proper operation of AIC2862, the
In order to avoid the poor output voltage ripple and low
following points should be managed comprehensively.
efficiency caused by instability, AIC2862 requires a
1. The input capacitor and VIN should be placed as
proper external compensation network to compensate
close as possible to each other to reduce the input
its feedback loop. In this external compensation
voltage ripple and noise.
network, the compensation resistor, RC, and the
2. The output loop, which is consisted of the inductor,
compensation capacitor, CC, are used to set the high-
the internal power switch, the Schottky diode and
frequency integrator gain and the integrator zero. C7 is
the output capacitor, should be kept as small as
used to cancel the zero caused by the output capacitor
possible.
and it’s ESR. While using the ceramic capacitor as the
output capacitor, C7 can be omitted due to the small
and wide.
4. Logically the large current on the converter should
ESR.
The system has one pole of importance, due to the
output capacitor, C3 and the load resistor. This poles
is located at:
FP1 =
3. The routes with large current should be kept short
1
2π × C3 × RLOAD
The system has one zero of importance, due to the
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.
compensation capacitor, Cc and the compensation
resistor, Rc. This zero is located at:
FZ1 =
1
2π × Cc × Rc
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AIC2862

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
e
2.55
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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