600 mA/1000 mA, 2.5 MHz Buck-Boost
DC-to-DC Converters
ADP2503/ADP2504
Rev. A
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 ©2008–2009 Analog Devices, Inc. All rights reserved.
FEATURES
1 mm height profile
Compact PCB footprint
Seamless transition between modes
38 A typical quiescent current
2.5 MHz operation enables 1.5 µH inductor
Input voltage: 2.3 V to 5.5 V
Fixed output voltage: 2.8 V to 5.0 V
Adjustable model output voltage range: 2.8 V to 5.5 V
600 mA (ADP2503) and 1000 mA (ADP2504) output options
Boost converter configuration with load disconnect
SYNC pin with three different modes
Power save mode (PSM) for improved light load efficiency
Forced fixed frequency operation mode
Synchronization with external clock
Internal compensation
Soft start
Enable/shutdown logic input
Overtemperature protection
Short-circuit protection
Undervoltage lockout protection
Small 10-lead 3 mm × 3 mm LFCSP (QFN) package
APPLICATIONS
Wireless handsets
Digital cameras/portable audio players
Miniature hard disk power supplies
USB powered devices
GENERAL DESCRIPTION
The ADP2503/ADP2504 are high efficiency, low quiescent current
step-up/step-down dc-to-dc converters that can operate at input
voltages greater than, less than, or equal to the regulated output
voltage. The power switches and synchronous rectifiers are
internal to minimize external part count. At high load currents,
the ADP2503/ADP2504 use a current-mode, fixed frequency
pulse-width modulation (PWM) control scheme for optimal
stability and transient response. To ensure the longest battery life
in portable applications, the ADP2503/ADP2504 have an optional
power save mode that reduces the switching frequency under
light load conditions. For wireless and other low noise applica-
tions where variable frequency power save mode may cause
interference, the logic control input sync forces fixed frequency
PWM operation under all load conditions.
The ADP2503/ADP2504 can run from input voltages between
2.3 V and 5.5 V, allowing single lithium or lithium polymer cell,
multiple alkaline or NiMH cells, PCMCIA, USB, and other stan-
dard power sources. The ADP2503/ADP2504 have fixed output
options, or using the adjustable model, the output voltage can
be programmed through an external resistor divider. Compensa-
tion is internal to minimize the number of external components.
During logic-controlled shutdown, the input is disconnected
from the output and draws less than 1 µA from the input source.
Operating as boost converters, the ADP2503/ADP2504 feature
a true load disconnect function that isolates the load from the
power source. Other key features include undervoltage lockout
to prevent deep battery discharge, and soft start to prevent input
current overshoot at startup.
TYPICAL APPLICATION CIRCUIT
SW1
1.5µH
PVIN
VIN
2
.3
V
TO 5.5V
VOUT
2.8V TO 5V
22µF10µF
ADP2503/ADP2504
VIN
VOUT
SW2
FB
SYNC1
1ALLOWS THE ADP2503/ADP2504 TO OPERATE IN
THREE DIFFERENT MODES.
EN
OFF
ON
PGND
AGND
0
7475-001
Figure 1.
ADP2503/ADP2504
Rev. A | Page 2 of 16
TABLE OF CONTENTS
Features .............................................................................................. 1
Applications ....................................................................................... 1
General Description ......................................................................... 1
Typical Application Circuit ............................................................. 1
Revision History ............................................................................... 2
Specifications ..................................................................................... 3
Absolute Maximum Ratings ............................................................ 4
Thermal Data ................................................................................ 4
Thermal Resistance ...................................................................... 4
ESD Caution .................................................................................. 4
Pin Configuration and Function Descriptions ............................. 5
Typical Performance Characteristics ............................................. 6
Theory of Operation ...................................................................... 11
Power Save Mode ........................................................................ 11
Soft Start ...................................................................................... 11
SYNC Function ........................................................................... 11
Enable ........................................................................................... 11
Undervoltage Lockout ............................................................... 12
Thermal Shutdown .................................................................... 12
Short-Circuit Protection ............................................................ 12
Reverse Current Limit ............................................................... 12
Applications Information .............................................................. 13
Inductor Selection ...................................................................... 13
Output Voltage Programming .................................................. 14
PCB Layout Guidelines .................................................................. 15
Outline Dimensions ....................................................................... 16
Ordering Guide .......................................................................... 16
REVISION HISTORY
8/09—Rev. 0 to Rev. A
Changes to Features Section, Figure 1, and General Description
Section ................................................................................................ 1
Changes to Feedback Voltage Parameter and EN, SYNC
Leakage Current Parameter, Table 1 .............................................. 3
Changes to Table 2 and Thermal Resistance Section ................... 4
Added Thermal Data Section ......................................................... 4
Changes to Figure 2 and Table 4 ..................................................... 5
Changes to Figure 12 ........................................................................ 7
Changes to Figure 17 ......................................................................... 8
Changes to SYNC Function Section ............................................ 11
Changes to Undervoltage Lockout Section ................................. 12
Changes to Table 6 .......................................................................... 13
Added Output Voltage Programming Section ........................... 14
Added Figure 30; Renumbered Sequentially .............................. 14
Changes to Ordering Guide .......................................................... 16
10/08—Revision 0: Initial Version
ADP2503/ADP2504
Rev. A | Page 3 of 16
SPECIFICATIONS
VIN = 3.6 V, VOUT = 3.3 V, @ TA = TJ = −40°C to +125°C for minimum/maximum specifications and TA = 25°C for typical specifications,
unless otherwise noted.1
Table 1.
Parameters Conditions Min Typ Max Unit
INPUT CHARACTERISTICS
Input Voltage Range 2.3 5.5 V
Undervoltage Lockout Threshold VIN rising 2.15 2.20 2.25 V
V
IN falling 2.10 2.14 2.20 V
OUTPUT CHARACTERISTICS
Output Voltage Range 2.8 5.5 V
Feedback Impedance 450 kΩ
Feedback Voltage ADP2503/ADP2504 adjustable output (PWM operation, no load) 490 500 510 mV
Output Voltage Initial Accuracy ADP2503/ADP2504 fixed output (PWM operation, no load) −2 +2 %
Load and Line Regulation VIN = 2.3 V to 3.6 V, ILOAD = 0 mA to 500 mA, forced PWM mode 0.5 %
V
IN = 2.3 V to 5.5 V, ILOAD = 0 mA to 500 mA, forced PWM mode 0.6 %
CURRENT CHARACTERISTICS
Quiescent Current (VIN) IOUT = 0 mA, VIN = EN = 3.6 V, device not switching 38 50 µA
Shutdown Current TA = TJ = −40°C to +85°C 0.2 1 µA
SWITCH CHARACTERISTICS
N-Channel Switches VIN = 3.6 V 150 mΩ
P-Channel Switches VIN = VOUT = 3.6 V 150 mΩ
P-Channel Leakage TJ = −40°C to +85°C 1 µA
Switch Current Limit
ADP2504 1.3 2.0 A
ADP2503 1.0 1.4 A
Reverse Current Limit 1.1 A
OSCILLATOR AND STARTUP
Oscillator Frequency 2.1 2.5 2.9 MHz
On Time PMOS1 (Buck Mode) Minimum duty cycle = 30% 130 ns
On Time NMOS2 (Boost Mode) Maximum duty cycle = 50% (×2) 200 ns
SYNC Clock Frequency 2.2 2.8 MHz
SYNC Clock Minimum Off Time 160 ns
LOGIC LEVEL CHARACTERISTICS
EN, SYNC Input High Threshold 1.2 V
EN, SYNC Input Low Threshold 0.4 V
EN, SYNC Leakage Current VEN = VIN, VSYNC = VIN −1 +0.1 +1 µA
THERMAL CHARACTERISTICS
Thermal Shutdown Threshold 150 °C
Thermal Shutdown Hysteresis 25 °C
1 All limits at temperature extremes are guaranteed via correlation using standard statistical quality control (SQC).
ADP2503/ADP2504
Rev. A | Page 4 of 16
ABSOLUTE MAXIMUM RATINGS
Table 2.
Parameter Rating
PVIN, VIN, SW1, SW2, VOUT, SYNC, EN, FB −0.3 V to +6 V
PGND to AGND −0.3 V to 0.3 V
Operating Ambient Temperature Range −40°C to +85°C
Operating Junction Temperature Range −40°C to +125°C
Storage Temperature Range −65°C to +150°C
Soldering Conditions JEDEC J-STD-020
ESD Human Body Model ±2000 V
ESD Charged Device Model ±1500 V
ESD Machine Model ±100 V
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.
THERMAL DATA
Absolute maximum ratings apply individually only, not in
combination.
The ADP2503/ADP2504 can be damaged when the junction
temperature limits are exceeded. Monitoring ambient tempera-
ture (TA) does not guarantee that the junction temperature (TJ)
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. In applications
with moderate power dissipation and low PCB thermal resis-
tance, the maximum ambient temperature can exceed the
maximum limit as long as the junction temperature is within
specification limits. TJ of the device is dependent on TA, the
power dissipation (PD) of the device, and the junction-to-
ambient thermal resistance (θJA) of the package. Maximum
TJ is calculated from TA and PD using the following formula:
TJ = TA + (PD × θJA)
θJA 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 applica-
tions where high maximum power dissipation exists, close
attention to thermal board design is required. The value of θJA
may vary, depending on PCB material, layout, and environmental
conditions. The specified values of θJA are based on a 4-layer,
4 inch × 3 inch circuit board. Refer to JEDEC JESD 51-9 for
detailed information on the board construction.
THERMAL RESISTANCE
θJA are specified for the worst-case conditions, that is, a device
soldered in a circuit board for surface-mount packages.
Table 3.
Package Type JA Unit
10-Lead LFCSP (QFN) 84 °C/W
ESD CAUTION
ADP2503/ADP2504
Rev. A | Page 5 of 16
PIN CONFIGURATION AND FUNCTION DESCRIPTIONS
07475-003
NOTES
1. CONNECT EXPOSED PAD TO PG ND.
1VOUT
2SW2
3PGND
4SW1
5PVIN
10 FB
9AGND
8VIN
7SYNC
6EN
TOP VIEW
(Not to scale)
ADP2503/
ADP2504
Figure 2. Pin Configuration
Table 4. Pin Function Descriptions
Pin No. Mnemonic Description
1 VOUT Output of the ADP2503/ADP2504. Connect the output capacitor between VOUT and PGND.
2 SW2 Power Switch 2 Connection. This is the internal connection to the input PMOS and NMOS switches. Connect
SW2 to the inductor with a short, wide track.
3 PGND Power GND. Connect the input and output capacitors and the PGND pin to a PGND plane.
4 SW1 Power Switch 1 Connection. This is the internal connection to the output PMOS and NMOS switches. Connect
SW1 to the inductor with a short, wide track.
5 PVIN Power Input. This the input to the buck-boost power switches. Place a 10 F capacitor between PVIN and
PGND as close as possible to the ADP2503/ADP2504.
6 EN Enable. Drive EN high to turn on the ADP2503/ADP2504. Bring EN low to put the part into shutdown mode.
7 SYNC The SYNC pin permits the ADP2503/ADP2504 to operate in three different modes.
Normal operation: with SYNC driven low, the ADP2503/ADP2504 operate at 2.5 MHz PWM mode for heavy
and medium loads, and moves to power save mode (PSM) mode for light loads.
Forced PWM operation: with SYNC driven high, the ADP2503/ADP2504 operate at fixed 2.5 MHz PWM mode
for all load conditions.
SYNC mode: to synchronize the ADP2503/ADP2504 switching to an external signal, drive this pin with a clock
between 2.2 MHz and 2.8 MHz. The SYNC signal must have on and off times greater than 160 ns.
8 VIN Analog Power Supply. This is the supply for the ADP2503/ADP2504 internal circuitry.
9 AGND Analog Ground.
10 FB Output Feedback. This is an input to the internal error amplifier and must be connected to VOUT on fixed
output versions; for the adjustable model, this is the voltage feedback.
EP Exposed pad Connect the exposed pad to PGND.
ADP2503/ADP2504
Rev. A | Page 6 of 16
TYPICAL PERFORMANCE CHARACTERISTICS
700
600
500
400
300
200
100
0
OUTPUT CURRENT (
A
)
2.82.3 3.3 3.8 4.3 4.8 5.3
INPUT VOLTAGE (V)
V
OUT
= 2.8V
V
OUT
= 3.5V
V
OUT
= 4.2V
V
OUT
= 4.5V
V
OUT
= 5.0V
V
OUT
= 3.3V
07475-114
Figure 3. ADP2503 Output Current vs. Input Voltage
1100
1000
900
800
700
600
500
400
300
200
100
0
OUTPUT CURRENT (A)
2.82.3 3.3 3.8 4.3 4.8 5.3
INPUT VOLTAGE (V)
V
OUT
= 2.8V
V
OUT
= 3.3V
V
OUT
= 3.5V
V
OUT
= 4.2V
V
OUT
= 4.5V
V
OUT
= 5.0V
07475-115
Figure 4. ADP2504 Output Current vs. Input Voltage
100
90
80
70
60
50
40
30
20
10
0
0.001 0.01
EFFICIENCY (%)
0.1 1
I
OUT
(A)
07475-103
V
IN
= 5.5V
V
IN
= 4.2V
V
IN
= 3.6V
V
IN
= 2.3V
Figure 5. Efficiency vs. Output Current, PWM Mode (VOUT = 5.0 V)
0.001 0.01 0.1 1
100
90
80
70
60
50
40
30
20
10
0
EFFICIENCY (%)
I
OUT
(A)
07475-104
V
IN
= 5.5V
V
IN
= 4.2V
V
IN
= 3.6V
V
IN
= 2.3V
Figure 6. Efficiency vs. Output Current, PSM and PWM Mode (VOUT = 5.0 V)
0.001 0.01 0.1 1
100
90
80
70
60
50
40
30
20
10
0
EFFICIENCY (%)
I
OUT
(A)
07475-109
V
IN
= 5.5V
V
IN
= 4.2V
V
IN
= 3.6V
V
IN
= 2.3V
Figure 7. Efficiency vs. Output Current, PWM Mode (VOUT = 3.3 V)
0.001 0.01 0.1 1
100
90
80
70
60
50
40
30
20
10
0
EFFICIENCY (%)
I
OUT
(A)
07475-108
V
IN
= 5.5V
V
IN
= 4.2V
V
IN
= 3.6V
V
IN
= 2.3V
Figure 8. Efficiency vs. Output Current, PSM and PWM Mode (VOUT = 3.3 V)
ADP2503/ADP2504
Rev. A | Page 7 of 16
0.001 0.01 0.1 1
100
90
80
70
60
50
40
30
20
10
0
EFFICIENCY (%)
I
OUT
(A)
07475-105
V
IN
= 5.5V
V
IN
= 4.2V
V
IN
= 3.6V
V
IN
= 2.3V
Figure 9. Efficiency vs. Output Current, PWM Mode (VOUT = 2.8 V)
0.001 0.01 0.1 1
100
90
80
70
60
50
40
30
20
10
0
EFFICIENCY (%)
I
OUT
(A)
07475-106
V
IN
= 5.5V
V
IN
= 4.2V
V
IN
= 3.6V
V
IN
= 2.3V
Figure 10. Efficiency vs. Output Current, PSM and PWM Mode (VOUT = 2.8 V)
100
90
80
70
60
50
40
30
20
10
0
2.3 2.8 3.3
EFFICIENCY (%)
3.8 4.3 4.8 5.3
V
IN
(V)
07475-107
I
OUT
= 500mA
I
OUT
= 100mA
I
OUT
= 10mA
Figure 11. Efficiency vs. Input Voltage (VOUT = 3.3 V)
3.35
3.33
3.31
3.29
3.27
3.25 0 0.1 0.2 0.3 0.4 0.5
I
OUT
(A)
V
OUT
(V)
0.6 0.7 0.8 0.9 1.0
07475-110
Figure 12. Load Regulation (VIN = 3.6 V, VOUT = 3.3 V)
2.8
2.7
2.6
2.5
2.4
2.3
2.2
2.3 2.7 3.1 3.5
FREQUENCY (MHz)
3.9 4.3 4.7 5.1 5.5
V
IN
(V)
07475-112
–40°C
+25°C
+85°C
Figure 13. Frequency vs. Input Voltage Over Temperature (VOUT = 3.3 V)
50
45
40
35
30
25
20
15
10
5
0
2.3 2.7 3.1 3.5
QUIESCENT CURRENT (µA)
3.9 4.3 4.7 5.1 5.5
V
IN
(V)
07475-113
Figure 14. Quiescent Current vs. Input Voltage (VOUT = 3.3 V)
ADP2503/ADP2504
Rev. A | Page 8 of 16
07475-005
CH1 50.0mV
BW
CH3 5.00V
BW
CH4 5.00V
BW
CH2 1.00V
BW
M40.0µs A CH2 3.40mV
4
2
1
3
T18.20%
V
IN
= 3.0V TO 3.6V
V
OUT
= 5.0V
V
OUT
SW2
SW1
V
IN
Figure 15. Line Transient, PWM Mode (VIN = 3.0 V to 3.6 V, VOUT = 5.0 V)
07475-006
CH1 50.0mV BW
CH3 5.00V BWCH4 5.00V BW
CH2 1.00V BWM40.0µs A CH2 3.40V
4
2
3
1
T 18.20%
VIN = 3.0V TO 3.6V
VOUT = 3.3V
VOUT
SW2
SW1
VIN
Figure 16. Line Transient, PWM Mode (VIN = 3.0 V to 3.6 V, VOUT = 3.3 V)
07475-007
CH1 50.0mV BW
CH3 5.00V BWCH4 5.00V BW
CH2 1.00V BWM40.0µs A CH2 3.40mV
4
2
3
1
T18.20%
VIN = 3.0V TO 3.6V
VOUT = 2.8V
VOUT
SW2
SW1
VIN
Figure 17. Line Transient, PWM Mode (VIN = 3.0 V to 3.6 V, VOUT = 2.8 V)
07475-008
CH1 100mV
BW
CH2 250mA Ω
CH3 5.00V
BW
CH4 5.00V
BW
M100µs A CH2 60.0mA
1
2
4
3
T 25.80%
V
IN
= 3.6V
V
OUT
= 3.3V
SW2
SW1
I
OUT
V
OUT
Figure 18. Load Transient (VIN = 3.6 V, VOUT = 3.3 V, IOUT = 100 mA to 350 mA)
07475-111
CH1 100mV
BW
CH3 5.00V
BW
CH4 5.00V
BW
CH2 250mA ΩM100µs A CH2 60.0mA
4
2
1
3
T23.00%
V
IN
= 3.6V
V
OUT
= 3.3V
SW2
SW1
I
OUT
V
OUT
Figure 19. Load Transient (VIN = 3.6 V, VOUT = 3.3 V, IOUT = 10 mA to 300 mA)
07475-010
CH1 100mV
BW
CH4 2.00V
BW
CH2 500mA ΩM100µs A CH2 –115mA
4
1
2
T 45.40%
V
IN
= 3.6V
V
OUT
= 3.3V
SW1
I
OUT
V
OUT
Figure 20. Mode Change by Load Transients, Load Rise (VIN = 3.6 V, VOUT = 3.3 V)
ADP2503/ADP2504
Rev. A | Page 9 of 16
07475-011
CH1 100mV
BW
CH4 2.00V
BW
CH2 500mA ΩM100µs A CH2 410mA
4
1
2
T 45.40%
V
IN
= 3.6V
V
OUT
= 3.3V
SW1
I
OUT
V
OUT
Figure 21. Mode Change by Load Transients, Load Fall (VOUT = 3.3 V)
07475-012
CH1 50.0mV
BW
CH4 5.00V
BW
CH3 5.00V
BW
CH2 250mA ΩM 400ns A CH3 2.40V
3
4
1
2
T 50.00%
V
IN
= 4.0V
V
OUT
= 3.3V
SW2
SW1
I
SW
V
OUT
Figure 22. Typical PWM Switching Waveform, Buck Operation (VOUT = 3.3 V)
07475-013
CH1 20.0mV
BW
CH4 5.00V
BW
CH3 5.00V
BW
CH2 250mA ΩM 400ns A CH4 2.40V
3
1
2
4
T 50.80%
V
IN
= 3.0V
V
OUT
= 3.3V
SW2
SW1
I
SW
V
OUT
Figure 23. Typical PWM Switching Waveform, Boost Operation (VOUT = 3.3 V)
07475-027
CH1 20.0mV
BW
CH4 5.00V
BW
CH3 5.00V
BW
CH2 250mA ΩM 400ns A CH4 2.40V
3
1
2
4
T 50.00%
V
IN
= 3.0V
V
OUT
= 3.3V
SW2
SW1
I
SW
V
OUT
Figure 24. Typical PWM Switching Waveform, Buck-Boost Operation
(VOUT = 3.3 V)
07475-015
CH1 100mV
BW
CH4 5.00V
BW
CH3 5.00V
BW
CH2 1.00A ΩM 4.00µs A CH2 820mA
3
4
1
2
T 15.20%
V
IN
= 3.0V
V
OUT
= 3.3V
SW2
SW1
I
SW
V
OUT
Figure 25. Typical PSM Switching Waveform, Buck-Boost Operation
(VOUT = 3.3 V)
07475-018
CH1 2.00V
BW
CH4 5.00V
BW
CH3 5.00V
BW
CH2 500mAΩ
BW
M 100µs A CH3 2.40V
4
1
3
2
T 9.400%
V
OUT
= 3.3V
EN
SW1
I
SW
V
OUT
Figure 26. Startup into PWM Mode (VOUT = 3.3 V, IOUT = 300 mA)
ADP2503/ADP2504
Rev. A | Page 10 of 16
07475-019
CH1 2.00V
BW
CH4 5.00V
BW
CH3 5.00V
BW
CH2 500mAΩ
BW
M 100µs A CH3 2.40V
4
1
3
2
T 9.400%
V
OUT
= 3.3V
EN
SW1
I
SW
V
OUT
Figure 27. Startup into PWM Mode (VOUT = 3.3 V, IOUT = 10 mA)
07475-023
CH1 2.00V
BW
CH4 5.00V
BW
CH3 5.00V
BW
CH2 500mAΩ
BW
M 100µs A CH3 2.40V
4
1
3
2
T 9.400%
V
OUT
= 3.3V
EN
SW1
I
SW
V
OUT
Figure 28. Startup into PSM Mode (VOUT = 3.3 V, IOUT = 10 mA)
ADP2503/ADP2504
Rev. A | Page 11 of 16
THEORY OF OPERATION
BAND GAP
REFERENCE
SYNC
PGND AGND
EN
PVIN
V
BAT = 2.3V
TO 5.5V
VIN
VOUT
SW1 SW2
1.5µH
EN
2.25V
UVLO
10µF 22µF
ADP2503/ADP2504
BIASING
ADP2503/ADP2504
PMOS1 PMOS2
NMOS1 NMOS2
THERMAL
PROTECTION
PWM CONTROL
OSCILLATOR
8
4
5
6
7
3 9
FB
–0.5V
07475-025
2
1
10
CS
SOFT START
Figure 29. ADP2503/ADP2504 Block Diagram
The ADP2503/ADP2504 are synchronous average current-
mode switching buck-boost regulators designed to maintain a
fixed output voltage VOUT from an input supply VIN that can be
greater than, equal to, or less than VOUT. When VIN is signifi-
cantly greater than VOUT, the device is in buck mode: PMOS2 is
always active, NMOS2 is always off, and the PMOS1 and NMOS1
switches constitute a buck converter. When VIN is significantly
lower than VOUT, the device is in boost mode: PMOS1 is always
active, NMOS1 is always off, and the NMOS2 and PMOS2
switches constitute a boost converter. When VIN is in the range
[VOUT ± 10%], the ADP2503/ADP2504 automatically enter the
buck-boost mode. In buck-boost mode, the two operations,
buck (PMOS1 and NMOS1 switching in antiphase) and boost
(NMOS2 and PMOS2 switching in antiphase), take place at each
period of the clock. This is aimed at maintaining the regulation
and keeping a minimal current ripple in the inductor to guaran-
tee good transient performances.
POWER SAVE MODE
When the SYNC pin is low, the ADP2503/ADP2504 can operate
in power save mode (PSM). In this mode, when the load current
becomes less than 75 mA nominally at VIN = 3.6 V, the control-
ler pulls up VOUT and then halts the switching regime until VOUT
goes back to a restart value. Then VOUT is pulled up again for a
new cycle. This minimizes the switching losses at light load. When
the load rises above 150 mA, the ADP2503/ADP2504 revert to
fixed PWM mode. This results in about 75 mA of hysteresis
between PSM and fixed PWM, preventing oscillations between
these two modes.
SOFT START
When the ADP2503/ADP2504 are started, VOUT is ramped from
0 V to its final programmed value in 200 s (typical). This limits
the inrush current to less than 600 mA for a nominal output
capacitor of 20 F. Because the VOUT start-up slope is constant,
the inrush current becomes larger if the output capacitor is
made larger.
SYNC FUNCTION
When the SYNC pin is high, PSM is deactivated. The ADP2503/
ADP2504 always operate in PWM using the internal oscillator.
When the SYNC pin is switching in the 2.1 MHz to 2.9 MHz
range, the regulator switching frequency slides to the fre-
quency applied on SYNC and then locks on it. When the
SYNC pin stops switching, the regulator switching frequency
slides back to the internal oscillator frequency.
ENABLE
The device starts operation with soft start when the EN pin
is brought high. Pulling the EN pin low forces the device into
shutdown, with a typical shutdown current of 0.2 µA.
In this mode, the PMOS power switches are turned off, the
NMOS power switches are turned on, and the control circuitry
is not enabled. For proper operation, the EN pin must be
terminated and must not be left floating.
ADP2503/ADP2504
Rev. A | Page 12 of 16
UNDERVOLTAGE LOCKOUT
The undervoltage lockout circuit prevents the device from oper-
ating incorrectly at low input voltages. It prevents the converter
from turning on the power switches under undefined conditions
and, therefore, prevents deep discharge of the battery supply.
VIN must be greater than 2.25 V to enable the converter. During
operation, if VIN drops below 2.10 V, the ADP2503/ADP2504
are disabled until the supply exceeds the UVLO rising threshold.
THERMAL SHUTDOWN
When the junction temperature, TJ, exceeds 150°C typical,
the device goes into thermal shutdown. In this mode, the power
switches are turned off. The device resumes operation when the
junction temperature again falls below 125°C typical.
SHORT-CIRCUIT PROTECTION
When the nominal inductor peak current value of 1.5 A is
reached, the ADP2503/ADP2504 first switch off the NMOS2
transistor if it is active. If the current thereafter continues to
increase by an extra amount of 200 mA, the PMOS1 transistor
is also switched off. This operation is reversible when the short
circuit stops. It allows the inductor current ripple to be mini-
mized close to 1.5 A and, thus, the controller to restore VOUT
even if a high load current is maintained after the short circuit.
REVERSE CURRENT LIMIT
In case of a short circuit on VOUT to a value greater than
expected, the inductor current becomes negative (reverse
current). The negative peak value is limited to 1.1 A by
deactivating the PMOS2 switch.
ADP2503/ADP2504
Rev. A | Page 13 of 16
APPLICATIONS INFORMATION
INDUCTOR SELECTION
The high 2.5 MHz switching frequency of the ADP2503/
ADP2504 allows for minimal output voltage ripple, while
minimizing inductor size and cost. Careful inductor selection
also optimizes efficiency and reduces electromagnetic interfe-
rence (EMI). The selection of the inductor value determines
the inductor current ripple and loop dynamics.
LfV
VVV
BuckpeakI
OSC
IN
OUT
IN
OUT
L
)(
)(,
Lf
V
V
VV
BoostpeakI
OSC
IN
OUT
IN
OUT
L
)(
)(,
where:
fOSC is the switching frequency (typically 2.5 MHz).
L is the inductor value in henries.
A larger inductor value reduces the current ripple (and, therefore,
the peak inductor current), but is physically larger in size with
increased dc resistance. Inductor values between 1 µH and
1.5 µH are suggested. The maximum inductor value to ensure
stability is 2.0 µH. For increased efficiency with the ADP2504,
it is suggested that a 1.5 µH inductor be used.
The inductor peak current is at the maximum in boost mode.
To determine the actual maximum inductor current in boost
mode, the input dc current should be estimated.
ηV
V
II
IN
OUT
MAXLOADMAXIN
1
)()(
where η is efficiency (assume η ≈ 0.85 to 0.90).
The saturation current rating of the inductor must be at least
IIN(MAX) + ILOAD/2.
Ceramic multilayer inductors can be used with lower current
designs for a reduced overall solution size and dc resistance
(DCR). These are available in low profile packages. Care must
be taken because these derate quickly as the inductor value is
increased, especially at higher operating temperatures.
Ferrite core inductors have good core loss characteristics as well as
reasonable dc resistance. A shielded ferrite inductor reduces the
EMI generated by the inductor.
Table 5. Sample of Recommended Inductors
Vendor
Value
(µH) Part No.
DCR
(mΩ)
ISAT
(A)
Dimensions
L × W × H
(mm)
Toko 1.2 DE2810C 55 1.7 2.8 × 2.8 × 1.0
Toko 1.5 DE2810C 60 1.5 2.8 × 2.8 × 1.0
Toko 1 MDT2520-CN 100 1.8 2.5 × 2 × 1.2
Murata 1 LQM2HP-G0 55 1.6 2.5 × 2 × 1
Murata 1.5 LQM2HP-G0 70 1.5 2.5 × 2 × 1
TDK 1.0 CPL2512T 90 1.5 2.5 × 1.5 × 1.2
TDK 1.5 CPL2512T 120 1.2 2.5 × 1.5 × 1.2
Coilcraft 1.0 LPS3010 85 1.7 3.0 × 3.0 × 0.9
Coilcraft 1.5 LPS3010 120 1.3 3.0 × 3.0 × 0.9
Taiyo
Yuden
1.5 NR3015T1 40 1.5 3.0 × 3.0 × 1.5
Output Capacitor Selection
The output capacitor selection determines the output voltage
ripple, transient response, and the loop dynamics of the
ADP2503/ADP2504. The output voltage ripple for a given
output capacitor is as follows:
OUT
OSC
IN
OUT
IN
OUT
OUT CfLV
VVV
BuckpeakV
2
8
)(
)(,
OSC
OUTOUT
IN
OUT
LOAD
OUT fVC
VVI
BoostpeakV
)(
)(,
If the ADP2503/ADP2504 are operating in buck mode, the
worst-case voltage ripple occurs for the highest input voltage,
VIN. If the ADP2503/ADP2504 are operating in boost mode, the
worst-case voltage ripple occurs for the lowest input voltage, VIN.
The maximum voltage overshoot, or undershoot, is inversely
proportional to the value of the output capacitor. To ensure
stability and excellent transient response, it is recommended
to use a minimum of 22 µF X5R 6.3 V or 2 × 10 µF X5R 6.3 V
capacitors at the output. The effective capacitance (includes
temperature and dc bias effects) needed for stability is 14 µF.
Table 6. Recommended Output Capacitors
Vendor Value Part No.
Dimensions
L × W × H (mm)
Murata 2 × 10 µF, 6.3 V GRM188R60J106ME47 1.6 × 0.8 × 0.8 (2)
TDK 2 × 10 µF, 6.3 V C1608JB0J106K 1.6 × 0.8 × 0.8 (2)
Murata 22 µF, 6.3 V GRM21BR60J226ME39 2 × 1.25 × 1.25
TDK 22 µF, 6.3 V C2012X5R0J226M 2 × 1.25 × 1.25
TDK 22 µF, 10 V C3216X5R1A226K 2 × 1.25 × 1.25
Murata 2 × 10 µF, 10 V GRM21BR71A106KE51L 2 × 1.25 × 1.25 (2)
ADP2503/ADP2504
Rev. A | Page 14 of 16
Input Capacitor Selection
The ADP2503/ADP2504 require an input capacitor to filter
noise on the VIN pin, and provide the transient currents while
maintaining constant input and output voltage. A 10 µF X5R/
X7R ceramic capacitor rated for 6.3 V is the minimum recom-
mended input capacitor. Increased input capacitance reduces
the amplitude of the switching frequency ripple on the battery.
Because of the dc bias characteristics of ceramic capacitors, a
0603, 6.3 V, X5R/X7R, 10 µF ceramic capacitor is preferable.
Table 7. Recommended Input Capacitors
Vendor Value Part No.
Dimensions
L × W × H
(mm)
Murata 10 µF, 6.3 V GRM188R60J106ME47 1.6 × 0.8 × 0.8
TDK 10 µF, 6.3 V C1608JB0J106K 1.6 × 0.8 × 0.8
OUTPUT VOLTAGE PROGRAMMING
The ADP2503/ADP2504 have an adjustable model where the
output is programmed through an external resistor divider.
The resistor divider is connected between VOUT and FB and
between FB and GND, and the combined total for the resistor
divider should be kept close to 400 kΩ. The typical voltage
reference (VREF) is 500 mV and depending on the output voltage
required, the following equation can be used to calculate the
value of the resistors:
REF
OUT V
R
RR
V
2
21
An example of the calculation for a required output voltage of
3.0 V follows.
V5.0
k60
k360
V0.3
SW1
1.5µH
PVIN
V
IN
2
.3
V
TO 5.5V
V
OUT
2.8V TO 5
V
20µF10µF
ADP2503/ADP2504
VIN
VOUT
SW2
FB
R1
R2
SYNC
EN
OFF
ON
PGND
AGND
0
7475-101
Figure 30. Typical Application Circuit for the Adjustable ADP2503/ADP2504
ADP2503/ADP2504
Rev. A | Page 15 of 16
PCB LAYOUT GUIDELINES
Poor layout can affect ADP2503/ADP2504 performance, caus-
ing electromagnetic interference (EMI) and electromagnetic
compatibility (EMC) performance, ground bounce, and voltage
losses. Poor layout can also affect regulation and stability. A good
layout is implemented using the following rules:
Place the inductor, input capacitor, and output capacitor
close to the IC using short tracks. These components carry
high switching frequencies and large tracks act like antennas.
Route the output voltage path away from the inductor and
SW node to minimize noise and magnetic interference.
Maximize the size of ground metal on the component side
to help with thermal dissipation.
Use a ground plane with several vias connecting to the
component side ground to further reduce noise interference
on sensitive circuit nodes.
07475-026
Figure 31. ADP2503/ADP2504 Evaluation Board for Fixed Output Voltages
ADP2503/ADP2504
Rev. A | Page 16 of 16
OUTLINE DIMENSIONS
031208-B
TOP VIEW
10
1
6
5
0.30
0.23
0.18
*EXPOSED
PAD
(BOTTOM VIEW)
PIN 1 INDEX
AREA
3.00
BSC SQ
SEATING
PLANE
0.80
0.75
0.70
0.20 REF
0.05 MAX
0.02 NOM
0.80 MAX
0.55 NOM
1.74
1.64
1.49
2.48
2.38
2.23
0.50
0.40
0.30
0.50 BSC
PIN 1
INDICATOR
(R 0.20)
*FOR PROPER CONNECTION OF THE EXPOSED PAD PLEASE REFER TO
THE PIN CONFIGURATION AND FUNCTION DESCRIPTIONS SECTION
OF THIS DATA SHEET.
Figure 32. 10-Lead Lead Frame Chip Scale Package [LFCSP_WD]
3 mm × 3 mm Body, Very Very Thin, Dual Lead
(CP-10-9)
Dimensions shown in millimeters
ORDERING GUIDE
Model Voltage
Max
Current
Temperature
Range Package Description
Package
Option Branding
ADP2503ACPZ-2.8-R71 2.8 V 0.6 A −40°C to +85°C 10-Lead Lead Frame Chip Scale Package [LFCSP_WD] CP-10-9 L9Y
ADP2503ACPZ-3.3-R71 3.3 V 0.6 A −40°C to +85°C 10-Lead Lead Frame Chip Scale Package [LFCSP_WD] CP-10-9 L9Z
ADP2503ACPZ-3.5-R71 3.5 V 0.6 A −40°C to +85°C 10-Lead Lead Frame Chip Scale Package [LFCSP_WD] CP-10-9 LAP
ADP2503ACPZ-4.2-R71 4.2 V 0.6 A −40°C to +85°C 10-Lead Lead Frame Chip Scale Package [LFCSP_WD] CP-10-9 LA0
ADP2503ACPZ-4.5-R71 4.5 V 0.6 A −40°C to +85°C 10-Lead Lead Frame Chip Scale Package [LFCSP_WD] CP-10-9 LA1
ADP2503ACPZ-5.0-R71 5.0 V 0.6 A −40°C to +85°C 10-Lead Lead Frame Chip Scale Package [LFCSP_WD] CP-10-9 LA2
ADP2503ACPZ-R71 Adj 0.6 A −40°C to +85°C 10-Lead Lead Frame Chip Scale Package [LFCSP_WD] CP-10-9 LE7
ADP2504ACPZ-2.8-R71 2.8 V 1 A −40°C to +85°C 10-Lead Lead Frame Chip Scale Package [LFCSP_WD] CP-10-9 L9T
ADP2504ACPZ-3.3-R71 3.3 V 1 A −40°C to +85°C 10-Lead Lead Frame Chip Scale Package [LFCSP_WD] CP-10-9 L85
ADP2504ACPZ-3.5-R71 3.5 V 1 A −40°C to +85°C 10-Lead Lead Frame Chip Scale Package [LFCSP_WD] CP-10-9 LAN
ADP2504ACPZ-4.2-R71 4.2 V 1 A −40°C to +85°C 10-Lead Lead Frame Chip Scale Package [LFCSP_WD] CP-10-9 L9U
ADP2504ACPZ-4.5-R71 4.5 V 1 A −40°C to +85°C 10-Lead Lead Frame Chip Scale Package [LFCSP_WD] CP-10-9 L9V
ADP2504ACPZ-5.0-R71 5.0 V 1 A −40°C to +85°C 10-Lead Lead Frame Chip Scale Package [LFCSP_WD] CP-10-9 L9W
ADP2504ACPZ-R71 Adj 1 A −40°C to +85°C 10-Lead Lead Frame Chip Scale Package [LFCSP_WD] CP-10-9 LE8
ADP2503CPZ-REDYKIT2 Evaluation Board for Fixed Output Voltages, 3.3 V and 5.0 V
ADP2504CPZ-REDYKIT2 Evaluation Board for Fixed Output Voltages, 2.8 V and 5.0 V
1 Z = RoHS Compliant Part.
2 Redykit contains two evaluation boards with the stated output voltages plus three devices of each available fixed output voltage.
©2008–2009 Analog Devices, Inc. All rights reserved. Trademarks and
registered trademarks are the property of their respective owners.
D07475-0-8/09(A)
