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Compact, 600 mA, 3 MHz,
Step-Down DC-to-DC Converter
Data Sheet
FEATURES
Peak efficiency: 95%
3 MHz fixed frequency operation
Typical quiescent current: 18 μA
Maximum load current: 600 mA
Input voltage: 2.3 V to 5.5 V
Uses tiny multilayer inductors and capacitors
Current mode architecture for fast load and line
transient response
100% duty cycle low dropout mode
Internal synchronous rectifier
Internal compensation
Internal soft start
Current overload protection
Thermal shutdown protection
Shutdown supply current: 0.2 μA
Available in
5-ball WLCSP
5-lead TSOT
ADP2108
GENERAL DESCRIPTION
The ADP2108 is a high efficiency, low quiescent current step-
down dc-to-dc converter manufactured in two different
packages. The total solution requires only three tiny external
components. It uses a proprietary, high speed current mode,
constant frequency PWM control scheme for excellent stability
and transient response. To ensure the longest battery life in
portable applications, the ADP2108 has a power save mode that
reduces the switching frequency under light load conditions.
The ADP2108 runs on input voltages of 2.3 V to 5.5 V, which
allows for single lithium or lithium polymer cell, multiple alkaline
or NiMH cell, PCMCIA, USB, and other standard power sources.
The maximum load current of 600 mA is achievable across the
input voltage range.
The ADP2108 is available in fixed output voltages of 3.3 V, 3.0 V,
2.5 V, 2.3 V, 1.82 V, 1.8 V, 1.5 V, 1.3 V, 1.2 V, 1.1 V, and 1.0 V. All
versions include an internal power switch and synchronous rect-
ifier for minimal external part count and high efficiency. The
ADP2108 has an internal soft start and is internally compensated.
During logic controlled shutdown, the input is disconnected
from the output and the ADP2108 draws less than 1 μA from
the input source.
Other key features include undervoltage lockout to prevent deep
battery discharge and soft start to prevent input current over-
shoot at startup. The ADP2108 is available in 5-ball WLCSP and
5-lead TSOT packages. The
ADP2109
provides the same features
and operations as the ADP2108 and has the additional function
of a discharge switch in the WLCSP package.
APPLICATIONS
PDAs and palmtop computers
Wireless handsets
Digital audio, portable media players
Digital cameras, GPS navigation units
TYPICAL APPLICATIONS CIRCUIT
ADP2108
2.3V TO 5.5V
VIN
4.7µF
ON
OFF
EN
FB
GND
07375-003
1µH
SW
1.0V TO 3.3V
10µF
Figure 1.
Rev. F
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 ©2008–2012 Analog Devices, Inc. All rights reserved.
ADP2108
TABLE OF CONTENTS
Features .............................................................................................. 1
Applications ....................................................................................... 1
General Description ......................................................................... 1
Typical Applications Circuit............................................................ 1
Revision History ............................................................................... 2
Specifications..................................................................................... 3
Absolute Maximum Ratings ............................................................ 4
Thermal Resistance ...................................................................... 4
ESD Caution .................................................................................. 4
Pin Configuration and Function Descriptions ............................. 5
Typical Performance Characteristics ............................................. 6
Theory of Operation ...................................................................... 11
Control Scheme .......................................................................... 11
PWM Mode ................................................................................. 11
Power Save Mode ........................................................................ 11
Data Sheet
Enable/Shutdown ....................................................................... 11
Short-Circuit Protection............................................................ 12
Undervoltage Lockout ............................................................... 12
Thermal Protection .................................................................... 12
Soft Start ...................................................................................... 12
Current Limit .............................................................................. 12
100% Duty Operation ................................................................ 12
Applications Information .............................................................. 13
External Component Selection ................................................ 13
Thermal Considerations............................................................ 14
PCB Layout Guidelines.............................................................. 14
Evaluation Board ............................................................................ 15
Outline Dimensions ....................................................................... 16
Ordering Guide .......................................................................... 17
REVISION HISTORY
1/12—Rev. E to Rev. F
Change to Table 3................................................................................... 4
Changes to Output Capacitor Section ......................................... 13
10/10—Rev. D to Rev. E
Changed −40°C to +85°C to −40°C to +125°C Throughout ......... 3
Changes to Ordering Guide .......................................................... 17
1/10—Rev. C to Rev. D
Changes to Ordering Guide .......................................................... 17
4/09—Rev. B to Rev. C
Changes to General Description Section ...................................... 1
2/09—Rev. A to Rev. B
Added 5-Lead TSOT Package ........................................... Universal
Changes to Absolute Maximum Ratings Section ......................... 4
Updated Outline Dimensions ....................................................... 16
Changes to Ordering Guide .......................................................... 17
11/08—Rev. 0 to Rev. A
Changes to Figure 4 .......................................................................... 6
Updated Outline Dimensions ....................................................... 16
9/08—Revision 0: Initial Version
Rev. F | Page 2 of 20
Data Sheet
SPECIFICATIONS
ADP2108
V
IN
= 3.6 V, V
OUT
= 1.8 V, T
J
= −40°C to +125°C for minimum/maximum specifications, and T
A
= 25°C for typical specifications, unless
otherwise noted.
1
Table 1.
Parameter
INPUT CHARACTERISTICS
Input Voltage Range
Undervoltage Lockout Threshold
OUTPUT CHARACTERISTICS
Output Voltage Accuracy
POWER SAVE MODE TO PWM CURRENT THRESHOLD
PWM TO POWER SAVE MODE CURRENT THRESHOLD
INPUT CURRENT CHARACTERISTICS
DC Operating Current
Shutdown Current
SW CHARACTERISTICS
SW On Resistance (WLCSP)
SW On Resistance (TSOT)
Current Limit
ENABLE CHARACTERISTICS
EN Input High Threshold
EN Input Low Threshold
EN Input Leakage Current
OSCILLATOR FREQUENCY
START-UP TIME
THERMAL CHARACTERISTICS
Thermal Shutdown Threshold
Thermal Shutdown Hysteresis
1
Test Conditions/Comments
Min
2.3
Typ
Max
5.5
2.3
2.25
+2
+2.5
Unit
V
V
V
%
%
mA
mA
V
IN
rising
V
IN
falling
PWM mode
V
IN
= 2.3 V to 5.5 V, PWM mode
2.05
−2
−2.5
2.15
85
80
I
LOAD
= 0 mA, device not switching
EN = 0 V, T
A
= T
J
= −40°C to +125°C
PFET
NFET
PFET
NFET
PFET switch peak current limit
18
0.2
320
300
380
260
1300
30
1.0
µA
µA
mΩ
mΩ
mΩ
mΩ
mA
V
V
µA
MHz
µs
°C
°C
1100
1.2
1500
EN = 0 V, 3.6 V
I
LOAD
= 200 mA
−1
2.5
0
3.0
0.4
+1
3.5
550
150
20
All limits at temperature extremes are guaranteed via correlation using standard statistical quality control (SQC).
Rev. F | Page 3 of 20
ADP2108
ABSOLUTE MAXIMUM RATINGS
Table 2.
Parameter
VIN, EN
FB, SW to GND
Operating Ambient Temperature Range
Operating Junction Temperature Range
Storage Temperature Range
Lead Temperature Range
Soldering (10 sec)
Vapor Phase (60 sec)
Infrared (15 sec)
ESD Human Body Model
ESD Charged Device Model
ESD Machine Model
Rating
−0.4 V to +6.5 V
−1.0 V to (V
IN
+ 0.2 V)
−40°C to +125°C
−40°C to +125°C
−65°C to +150°C
−65°C to +150°C
300°C
215°C
220°C
±1500 V
±500 V
±100 V
Data Sheet
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 (P
D
) of the device, 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 (P
D
) using the formula
T
J
= T
A
+ (P
D
× θ
JA
).
THERMAL RESISTANCE
θ
JA
is specified for a device mounted on a JEDEC 2S2P PCB.
Table 3. Thermal Resistance
Package Type
5-Ball WLCSP
5-Lead TSOT
θ
JA
105
170
Unit
°C/W
°C/W
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.
Absolute maximum ratings apply individually only, not in
combination. Unless otherwise specified, all other voltages
are referenced to GND.
The ADP2108 can be damaged when the junction temperature
limits are exceeded. Monitoring ambient temperature does not
guarantee that T
J
is within the specified temperature limits.
In applications with high power dissipation and poor thermal
resistance, the maximum ambient temperature may have to
be derated.
ESD CAUTION
Rev. F | Page 4 of 20
