Low Duty Cycle, 600 mA, 3 MHz Synchronous
Step-Down DC-to-DC Converter
ADP2102
FEATURES
Input voltage range: 2.7 V to 5.5 V
600 mA maximum load current
95% efficiency
Low duty cycle operation
Only 3 tiny external ceramic components
3 MHz typical operating frequency
Fixed output voltage from 0.8 V to 1.875 V
Adjustable output voltage up to 3.3 V
0.01 μA shutdown supply current
Automatic power save mode
Internal synchronous rectifier
Internal soft start
Internal compensation
Enable/shutdown logic input
Undervoltage lockout
Current limit protection
Thermal shutdown
Small 8-lead, 3 mm × 3 mm LFCSP package
GENERAL DESCRIPTION
The ADP2102 is a synchronous step-down dc-to-dc converter
that converts a 2.7 V to 5.5 V unregulated input voltage to a lower
regulated output voltage with up to 95% efficiency and 1%
accuracy. The low duty cycle capability of the ADP2102 is ideal for
USB applications or 5 V systems that power up submicron subvolt
processor cores. Its 3 MHz typical operating frequency and excel-
lent transient response allow the use of small, low cost 1 μH
inductors and 2.2 μF ceramic capacitors. At medium-to-high
load currents, it uses a current mode, pseudofixed frequency pulse-
width modulation to extend battery life. To ensure the longest
battery life in portable applications, the ADP2102 has a power save
mode (PSM) that reduces the switching frequency under light
load conditions to significantly reduce quiescent current.
The ADP2102 is available in both fixed and adjustable output
voltage options with 600 mA maximum output current. The preset
output voltage options voltage are 1.875 V, 1.8 V, 1.5 V, 1.375 V,
1.25 V, 1.2 V, 1.0 V, and 0.8 V. The adjustable voltage option is
available from 0.8 V to 3.3 V. The ADP2102 requires only three
external components and consumes 0.01 μA in shutdown mode.
The ADP2102 is available in an 8-lead LFCSP package and is
specified for the −40 °C to +85 °C temperature range.
APPLICATIONS
USB powered devices
WLAN and gateways
Point of loads
Processor core power from 5 V
Digital cameras
PDAs and palmtop computers
Portable media players, GPS
TYPICAL PERFORMANCE CHARACTERISTICS
100
95
90
V
IN
= 2.7V
V
IN
= 3V
V
OUT
= 1.375V
T
A
= 25°C
TYPICAL APPLICATIONS CIRCUIT
INPUT VOLTAGE
2.7V TO 5.5V
C
IN
2.2µF
L
V
IN
LX
1µH
OUTPUT VOLTAGE
0.8V TO 1.875V
C
OUT
2.2µF
EFFICIENCY (%)
85
80
75
70
65
V
IN
= 3.6V
V
IN
= 4.2V
FORCED
CCM
ADP2102
MODE
EN
FB/OUT
GND
OFF
100
LOAD CURRENT (mA)
1000
Figure 1.
06631-052
60
10
Figure 2.
Rev. B
Information furnished by Analog Devices is believed to be accurate and reliable. However, no
responsibility is assumed by Analog Devices for its use, nor for any infringements of patents or other
rights of third parties that may result from its use. Specifications subject to change without notice. No
license is granted by implication or otherwise under any patent or patent rights of Analog Devices.
Trademarks and registered trademarks are the property of their respective owners.
One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.
Tel: 781.329.4700
www.analog.com
Fax: 781.461.3113
©2007 Analog Devices, Inc. All rights reserved.
06631-001
DCM/
CCM
ON
ADP2102
TABLE OF CONTENTS
Features .............................................................................................. 1
Applications....................................................................................... 1
General Description ......................................................................... 1
Typical Performance Characteristics ............................................. 1
Typical Applications Circuit............................................................ 1
Revision History ............................................................................... 2
Specifications..................................................................................... 3
Absolute Maximum Ratings............................................................ 4
Thermal Resistance ...................................................................... 4
Boundary Condition.................................................................... 4
ESD Caution.................................................................................. 4
Pin Configuration and Function Descriptions............................. 5
Typical Performance Characteristics ............................................. 6
Theory of Operation ...................................................................... 13
Control Scheme .......................................................................... 13
Constant On-Time Timer ......................................................... 13
Forced Continuous Conduction Mode ................................... 13
Power Save Mode........................................................................ 13
Synchronous Rectification ........................................................ 14
Current Limit .............................................................................. 14
Soft Start ...................................................................................... 15
Enable........................................................................................... 15
Undervoltage Lockout ............................................................... 15
Thermal Shutdown .................................................................... 15
Applications Information .............................................................. 16
Inductor Selection ...................................................................... 16
Input Capacitor Selection.......................................................... 16
Output Capacitor Selection....................................................... 16
Typical Applications Circuits.................................................... 17
Setting the Output Voltage........................................................ 19
Efficiency Considerations ......................................................... 19
Thermal Considerations............................................................ 20
Design Example.......................................................................... 20
Circuit Board Layout Recommendations ................................... 22
Recommended Layout............................................................... 22
Outline Dimensions ....................................................................... 24
Ordering Guide .......................................................................... 24
REVISION HISTORY
9/07—Rev. A to Rev. B
Changes to Features, Applications, and General Description .... 1
Changes to Table 4............................................................................ 5
Changes to Table 6.......................................................................... 17
Changes to Table 7.......................................................................... 19
Changes to Circuit Board Layout Recommendations Section.... 21
Updated Outline Dimensions ....................................................... 23
Changes to Ordering Guide .......................................................... 23
6/07—Rev. 0 to Rev. A
Changes to Ordering Guide .......................................................... 23
6/07—Revision 0: Initial Version
Rev. B | Page 2 of 24
ADP2102
SPECIFICATIONS
V
IN
= 3.6 V, EN = V
IN
, MODE = V
IN
, T
A
= 25°C, unless otherwise noted.
Bold values
indicate −40°C ≤ T
A
≤ +85°C.
1
Table 1.
Parameter
INPUT CHARACTERISTICS
Input Voltage Range
2
Undervoltage Lockout Threshold
Undervoltage Lockout Hysteresis
OUTPUT CHARACTERISTICS
Output Voltage Range
Output Voltage Range
Output Voltage Initial Accuracy
Load Regulation
Line Regulation
FEEDBACK CHARACTERISTICS
FB Regulation Voltage
FB Bias Current
FB Impedance
CURRENT CHARACTERISTICS
Operating Current
Shutdown Current
Output Current
LX (SWITCH NODE) CHARACTERISTICS
LX On Resistance
LX Leakage Current
LX Minimum Off-Time
LX On-Time
Conditions
Min
2.7
2.2
Typ
Max
5.5
2.5
Unit
V
V
mV
V
V
%
%
%
%
mV
nA
kΩ
μA
μA
mA
mΩ
mΩ
μA
ns
ns
ns
ns
ns
ns
ns
ns
ns
ns
ns
ns
ns
A
V
V
μA
μs
°C
°C
V
IN
rising
2.4
220
ADP2102-xx
ADP2102-ADJ
ADP2102-xx, T
A
= 25°C, I
LOAD
= 0 mA
ADP2102-xx, −40°C ≤T
A
≤ 85°C, I
LOAD
= 0 mA
V
OUT
= 0.8 V to 1.875 V, I
LOAD
= 0 mA to 600 mA
V
IN
= 2.7 V to 5.5 V, I
LOAD
= 10 mA
ADP2102-ADJ
ADP2102-ADJ, ADP2102-0.8
ADP2102-xx
ADP2102 PSM mode, I
LOAD
= 0 mA
EN = 0 V
ADP2102, V
IN
= 2.7 V to 5.5 V
P-channel switch, I
LX
= 100 mA
N-channel synchronous rectifier, I
LX
= 100 mA
V
IN
= 5.5 V, V
LX
= 0 V, 5.5 V
ADP2102-xx, ADP2102-ADJ
ADP2102-0.8
ADP2102-1.0
ADP2102-1.2
ADP2102-1.25
ADP2102-1.375
ADP2102-1.5
ADP2102-1.8
ADP2102-1.875
ADP2102-ADJ-1.2
ADP2102-ADJ-1.5
ADP2102-ADJ-1.875
ADP2102-ADJ-3.3 (V
IN
= 5 V)
0.8
0.8
−1
−2
0.5
0.3
784
800
375
70
0.01
1.875
3.3
+1
+2
816
50
99
1
600
600
400
1
105
135
160
169
195
210
260
270
170
210
275
270
325
200
100
87
107
131
133
165
182
220
237
131
177
226
238
1
55
70
100
103
135
150
180
190
80
155
200
198
Valley Current Limit
ENABLE, MODE CHARACTERISTICS
EN, MODE Input High Threshold
EN, MODE Input Low Threshold
EN, MODE Input Leakage Current
SOFT START PERIOD
THERMAL CHARACTERISTICS
Thermal Shutdown Threshold
Thermal Shutdown Hysteresis
1
2
1.3
V
IN
= 5.5 V, EN = MODE = 0 V, 5.5 V
250
500
150
15
0.4
1
800
All limits at temperature extremes are guaranteed via correlation using standard statistical quality control (SQC).
The input voltage (V
IN
) range over which the rest of the specifications are valid. The part operates as expected until V
IN
goes below the UVLO threshold.
Rev. B | Page 3 of 24
ADP2102
ABSOLUTE MAXIMUM RATINGS
Table 2.
Parameter
AVIN, EN, MODE, FB/OUT to AGND
LX to PGND
PVIN to PGND
PGND to AGND
AVIN to PVIN
Operating Ambient Temperature Range
Junction Temperature Range
Storage Temperature Range
Soldering Conditions
1
THERMAL RESISTANCE
Rating
−0.3 V to +6 V
−0.3 V to (V
IN
+ 0.3 V)
−0.3 V to +6 V
−0.3 V to +0.3 V
−0.3 V to +0.3 V
−40°C to +85°C
1
−40°C to +125°C
−65°C to +150°C
JEDEC J-STD-020
The ADP2102 can be damaged when junction temperature limits are exceeded.
Monitoring ambient temperature does not guarantee that T
J
is within the
specified temperature limits. In applications where high power dissipation
and poor thermal resistance are present, the maximum ambient temperature
may have to be derated. In applications with moderate power dissipation
and low PCB thermal resistance, the maximum ambient temperature can
exceed the maximum limit as long as the junction temperature is within
specification limits. The junction temperature (T
J
) of the device is dependent
on the ambient temperature (T
A
), the power dissipation of the device (PD),
and the junction-to-ambient thermal resistance of the package (θ
JA
). Maximum
junction temperature (T
J
) is calculated from the ambient temperature (T
A
)
and power dissipation (PD) using the formula
T
J
=
T
A
+ (θ
JA
×
PD).
Unless
otherwise specified, all other voltages are referenced to AGND.
Junction-to-ambient thermal resistance (θ
JA
) of the package is
based on modeling and calculation using a 4-layer board. The
junction-to-ambient thermal resistance is highly dependent on
the application and board layout. In applications where high
maximum power dissipation exists, attention to thermal board
design is required. The value of θ
JA
may vary, depending on PCB
material, layout, and environmental conditions. Specified value
of θ
JA
is based on a 4-layer, 4 in × 3 in, 2 1/2 oz copper board,
as per JEDEC standards. For more information, see Application
Note AN-772,
A Design and Manufacturing Guide for the Lead
Frame Chip Scale Package (LFCSP).
Table 3. Thermal Resistance
Package Type
8-Lead LFCSP
Maximum Power Dissipation
θ
JA
54
0.74
Unit
°C/W
W
BOUNDARY CONDITION
Natural convection, 4-layer board, exposed pad soldered to PCB.
Stresses above those listed under Absolute Maximum Ratings
may cause permanent damage to the device. This is a stress
rating only; functional operation of the device at these or any
other conditions above those indicated in the operational
section of this specification is not implied. Exposure to absolute
maximum rating conditions for extended periods may affect
device reliability.
ESD CAUTION
Rev. B | Page 4 of 24
ADP2102
PIN CONFIGURATION AND FUNCTION DESCRIPTIONS
MODE 1
EN 2
FB/OUT 3
AGND 4
8 AVIN
ADP2102
TOP VIEW
(Not to Scale)
7 PVIN
06631-003
6 LX
5 PGND
Figure 3. Pin Configuration
Table 4. Pin Function Descriptions
Pin
No.
1
2
3
Mnemonic
MODE
EN
FB/OUT
Description
Mode Input. To set the ADP2102 to forced continuous conduction mode (CCM), drive MODE high. To set the ADP2102
to power save mode/auto mode (PSM), drive MODE low.
Enable Input. Drive EN high to turn on the ADP2102. Drive EN low to turn it off and reduce the input current to 0.1 μA.
This pin cannot be left floating.
Output Sense Input or Feedback Input. For fixed output versions, OUT is the top of the internal resistive voltage
divider. Connect OUT to the output voltage. For adjustable (no suffix) versions, FB is the input to the error amplifier.
Drive FB through a resistive voltage divider to set the output voltage. The FB regulation threshold is 0.8 V.
Analog Ground. Connect AGND to PGND at a single point as close to the ADP2102 as possible. The exposed paddle is
electrically common with the analog ground pin.
Power Ground.
Switch Output. LX is the drain of the P-channel MOSFET switch and the N-channel synchronous rectifier. Connect the
output LC filter between LX and the output voltage.
Power Source Input. Drive PVIN with a 2.7 V to 5.5 V power source. A ceramic bypass capacitor of 2.2 μF or greater is
required on this pin to the nearest PGND plane.
Power Source Input. AVIN is the supply for the ADP2102 internal circuitry. This pin can be connected in three different ways.
For noise reduction, place an external RC filter between PVIN and AVIN. The recommended values for the
external RC filter are 10 Ω and 0.1 μF, respectively. This configuration can be used for all loads.
For light-to-medium loads up to 300 mA, the AVIN pin and the PVIN pin can be shorted together.
For light-to-heavy loads (greater than 300 mA), bypass the AVIN pin with a 1 pF to 0.01 μF capacitor to the
nearest PGND plane. Do not short the AVIN and PVIN pins when using only a bypass capacitor.
4
5
6
7
8
AGND
PGND
LX
PVIN
AVIN
Rev. B | Page 5 of 24
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