Evaluation Board for Step-Down,
DC-to-DC Converter Solution
EVAL-ADP2102
Rev. A
Evaluation boards are only intended for device evaluation and not for production purposes.
Evaluation boards are supplied “as is” and without warranties of any kind, express, implied, or
statutory including, but not limited to, any implied warranty of merchantability or fitness for a
particular purpose. No license is granted by implication or otherwise under any patents or other
intellectual property by application or use of evaluation boards. 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. Analog Devices reserves the right to change devices or specifications at any time
without notice. Trademarks and registered trademarks are the property of their respective owners.
Evaluation boards are not authorized to be used in life support devices or systems.
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 ©2007–2008 Analog Devices, Inc. All rights reserved.
FEATURES
95% efficiency
Input voltage range: 2.7 V to 5.5 V
Fixed output voltage range: 0.8 V to 1.875 V
Adjustable output voltage range from 0.8 V to 3.3 V
Enable/shutdown logic input
Selectable PSM/PWM mode
Operating temperature range: −40°C to +125°C
GENERAL DESCRIPTION
The ADP2102 evaluation board is a complete step-down, dc-to-dc
converter solution using the ADP2102 step-down, dc-to-dc
converter. It provides a ±1% accurate (±2% over all conditions)
regulated output voltage with load currents up to 600 mA. It
comes in two versions: fixed output with output voltages ranging
from 0.8 V to 1.875 V and adjustable output with output voltages
ranging from 0.8 V to 3.3 V. Refer to the Ordering Guide for
details on the available models.
The ADP2102 is a synchronous, step-down, dc-to-dc converter,
which uses a constant on-time, valley current mode control
scheme to regulate the output voltage. At medium-to-heavy
load currents, the ADP2102 operates in continuous conduction
mode (CCM) for high efficiency and smoothly transitions to
a power-save mode (PSM) at light loads to conserve power.
The power switch and synchronous rectifier are integrated for
minimal external part count and high efficiency. The ADP2102
is optimized for operation with small ceramic inductors and
tiny ceramic capacitors to deliver the maximum output power
per square inch of the PCB board area.
It is recommended that this evaluation board data sheet be read
in conjunction with the ADP2102 data sheet, which provides
more detailed information about the converter.
FUNCTIONAL BLOCK DIAGRAM
06935-001
Figure 1. ADP2102 Evaluation Board
EVAL-ADP2102
Rev. A | Page 2 of 12
TABLE OF CONTENTS
Features .............................................................................................. 1
General Description ......................................................................... 1
Functional Block Diagram .............................................................. 1
Revision History ............................................................................... 2
Evaluation Board Hardware ............................................................ 3
Powering Up the Evaluation Board ............................................ 3
Measuring Evaluation Board Performance .................................. 3
Modifying the Evaluation Board ................................................ 4
Measurement Setup ...........................................................................5
Typical Performance Characteristics ..............................................6
Circuit Board Layout Recommendations ......................................7
Evaluation Board Schematics and Artwork ...................................8
Ordering Information .................................................................... 10
Bill of Materials ........................................................................... 10
Ordering Guide .......................................................................... 10
ESD Caution................................................................................ 10
REVISION HISTORY
6/08—Rev. 0 to Rev. A
Changes to Features Section............................................................ 1
Changes to General Description Section ...................................... 1
Changes to Turning on the Evaluation Board Section ................ 3
Changes to Modifying the Evaluation Board Section.................. 4
Deleted Figure 4 and Figure 7; Renumbered Sequentially .......... 6
Deleted Pin Configuration and Function Descriptions
Section ................................................................................................ 8
Changes to Figure 7 and Figure 8 ................................................... 8
Changes to Table 1 and Table 2 ..................................................... 10
Changes to Ordering Guide .......................................................... 10
7/07—Revision 0: Initial Version
EVAL-ADP2102
Rev. A | Page 3 of 12
EVALUATION BOARD HARDWARE
POWERING UP THE EVALUATION BOARD
The ADP2102 evaluation boards are supplied fully assembled
and tested. Before applying power to the evaluation board,
follow the procedures in this section.
Jumper JP2
Before turning on the ADP2102 evaluation board, make sure
that all the components are present, but that Jumper JP2 is
removed. Jumper JP2 enables the part.
Jumper JP1
The ADP2102 can be configured to operate in low noise
continuous conduction mode (CCM) or in power-save mode
(PSM), depending on the MODE pin polarity. If the MODE pin
is pulled high, ADP2102 operates in forced continuous conduction
mode, and if the MODE pin is pulled low, ADP2102 operates in
power-save mode.
Input Power Source
Before connecting the power source to the ADP2102 evaluation
board, make sure it is turned off. If the input power source
includes a current meter, use that meter to monitor the input
current. Connect the positive terminal of the power source to the
VIN terminal on the evaluation board, and the negative terminal of
the power source to the GND terminal of the evaluation board. If
the power source does not include a current meter, connect a
current meter in series with the input source voltage. Connect the
positive lead (+) of the power source to the ammeter positive (+)
connection, the negative lead (−) of the power source to the GND
terminal on the evaluation board, and the negative lead (−) of the
ammeter to the VIN terminal on the board.
Output Load
Although the ADP2102 evaluation board can sustain the sudden
connection of the load, it is possible to damage the load if it is not
properly connected. Make sure the board is turned off before con-
necting the load. If the load includes an ammeter, or if the current
is not measured, connect the load directly to the evaluation board,
with the positive (+) load connection to the VOUT terminal and
negative (−) load connection to the GND terminal. If an ammeter
is used, connect it in series with the load: connect the positive (+)
ammeter terminal to the evaluation board VOUT terminal, the
negative (−) ammeter terminal to the positive (+) load terminal,
and the negative (−) load terminal to the evaluation board GND
terminal.
Once the load is connected, make sure it is set to the proper
current before powering the ADP2102 evaluation board.
Input and Output Voltmeters
Measure the input and output voltages with voltmeters. Make
sure that the voltmeters are connected to the appropriate
evaluation board terminals and not to the load or power source
themselves. If the voltmeters are not connected directly to the
evaluation board, the measured voltages would be incorrect due
to the voltage drop across the leads and/or connections between
the evaluation board, the power source, and/or the load.
Connect the input voltage measuring voltmeter positive termi-
nal (+) to the evaluation board VIN terminal, and the negative
(−) terminal to the evaluation board GND terminal. Connect
the output voltage measuring voltmeter positive (+) terminal
to the evaluation board VOUT terminal and the negative (−)
terminal to the evaluation board GND terminal.
Turning On the Evaluation Board
Once the power source and load are connected to the ADP2102
evaluation board, the board can be powered for operation. Slowly
increase the input power source voltage until the input voltage
exceeds the minimum input operating voltage of 2.7 V. Insert
Jumper JP2 and check to see if the output voltage rises to the regu-
lated output voltage (for example,1.2 V for the ADP2102-1.2-
EVALZ). Ensure that the minimum input supply voltage is greater
than 4.5 V for powering up the adjustable ADP2102–4-EVALZ.
The input voltage range for the 2.5 V to 3.3 V adjustable output
voltage option is from 4.5 V < VIN < 5.5 V only.
If the load is not already enabled, enable the load; check that it is
drawing the proper current and that the output voltage maintains
voltage regulation.
MEASURING EVALUATION BOARD PERFORMANCE
Measuring Output Voltage Ripple
To observe the output voltage ripple, place an oscilloscope
probe across the output capacitor (C2) with the probe ground
lead at the negative (−) capacitor terminal and the probe tip at
the positive (+) capacitor terminal. Set the oscilloscope to ac,
20 mV/division, and 2 µs/division time base.
Measuring the Switching Waveform
To observe the switching waveform with an oscilloscope, place
the oscilloscope probe tip at the end of the inductor that is
connected to the LX pin with the probe ground at GND. Set the
oscilloscope to dc, 2 V/division, and 2 µs/division time base.
The switching waveform must alternate between 0 V and
approximately the input voltage.
Measuring Load Regulation
The load regulation must be tested by increasing the load at the
output and looking at the change in output voltage. To mini-
mize voltage drop, use short low resistance wires, especially for
heavy loads.
EVAL-ADP2102
Rev. A | Page 4 of 12
Measuring Line Regulation
Vary the input voltage and examine the change in the output
voltage. In forced continuous conduction mode, the output
voltage ripple is small (<50 mV), but in power-save mode, the
output voltage ripple can be as large as 50 mV.
Measuring Efficiency
The efficiency, η, is measured by comparing the input power
with the output power.
ININ
OUTOUT
IV
IV
×
×
=η
Measure the input and output voltages as close as possible to the
input and output capacitors to reduce the effect of IR drops.
Measuring Inductor Current
The inductor current can be measured by removing one end
of the inductor from its pad and connecting a current loop in
series with it. Then a current probe can be used to measure the
current flowing through the current loop, as shown in Figure 2.
MODIFYING THE EVALUATION BOARD
The ADP2102 evaluation board is supplied fully assembled and
tested for proper operation. It comes in two versions: fixed output
with output voltages ranging from 0.8 V to 1.875 V and adjustable
output with output voltages ranging from 0.8 V to 3.3 V. Refer
to the Ordering Guide for model details.
Changing the Output Voltage for the Adjustable Option
The ADP2102-x-EVALZ output regulation voltage can be changed
from 3.3 V to output voltages as low as 0.8 V by altering its
external components. The output regulation voltage of fixed
output voltage boards cannot be changed.
The output regulation voltage of adjustable voltage boards is set by
a resistive voltage divider consisting of Resistor R1 and Resistor R2.
The output regulation voltage is determined by the equation
VOUT = VFB (1 + R1/R2)
where:
VOUT is the regulated output voltage (V).
VFB = 0.8 V, the feedback voltage and the internal reference.
R1 is the feedback resistor from VOUT to VFB.
R2 is the feedback resistor from VFB to GND.
To set the output regulation voltage to the desired value, first
determine the value of the bottom resistor, R2, by
R2 = VFB/ISTRING
where:
VFB = 0.8 V, the internal reference.
ISTRING is the resistive divider string current (8 µA nominally).
Once R2 is determined, calculate the value of the top resistor,
R1, by
R1 = R2 (VOUT − VFB)/(VFB)
For example, to set the output regulation voltage of the
ADP2102-4-EVALZ to 3.0 V, calculate the value of Resistor R1
and Resistor R2.
R2 = VFB/ISTRING = 0.8 V/8 µA = 100 k
R1 = R2 (VOUT − VFB)/ (VFB)
= 100 k (3.0 V − 0.8 V)/(0.8 V) = 275 k
Refer Table 1 for the recommended VOUT configurations to
ensure stable operation.
A feedforward capacitor is required across the top resistor, R1,
for adjustable outputs greater than 1.875 V. This capacitor
provides a better transient response for medium to high load
steps. This feedforward capacitor provides additional phase
margin by creating a zero along with Resistor R1 at a frequency
given by
()()
2/2
1
CO
fR1
CFF ××
=
π
For example, in a 5 V input to 3.3 V output application, if the
output capacitor is 4.7 µF, a 6.8 pF feedforward capacitor is
required. This is based on a loop crossover frequency (fCO) of
150 kHz for a 4.7 µF capacitor.
Changing the Load Transient Response
The ADP2102 evaluation board load transient response can be
altered by changing the output capacitor, COUT. Ceramic
output capacitors are recommended for the ADP2102. By
default, the load transient response of the ADP2102 evaluation
board is set to 2% of the output voltage for a 600 mA load
transient. When using additional capacitance for better load
transient performance, the loss of capacitance due to dc bias
should be taken into account.
Table 1. ADP2102-x-EVALZ Configurations for VOUT
VOUT
(V)
R1
(kΩ)
R2
(kΩ)
CFF
(pF)
L1
(μH)
CIN
(pF)
COUT
(pF)
0.8 1 80.6 None 2.2 2.2 4.7
1.0 20 100 None 2.2 2.2 4.7
1.2 49.9 100 None 2.2 2.2 4.7
1.25 56.2 100 None 2.2 2.2 4.7
1.375 71.5 100 None 2.2 2.2 4.7
1.5 88.7 100 None 2.2 2.2 4.7
1.8 124 100 None 2.2 2.2 4.7
1.875 133 100 None 2.2 2.2 4.7
2.0 150 100 15 2.2 2.2 4.7
2.5 215 100 10 2.2 2.2 4.7
3.0 274 100 8.2 2.2 2.2 4.7
3.3 316 100 6.8 2.2 2.2 4.7
EVAL-ADP2102
Rev. A | Page 5 of 12
MEASUREMENT SETUP
VD 1S DIV
mVVCH
VPOS
NVER T
DVADVA ADD
VD 1S DIV
mVV
1V SEP
OFF
0V H
0V V
OFF
0V H
0V V
1V SEP AT N ORW
EVE
OSCILLOSCOPE
INDUCTOR
CURRENT
WAVEFORM
LX NODE
WAVEFORM
OUTPUT
VOLTAGE
WAVEFORM
06935-002
ELECTRONIC LOAD
VOLTMETER
V
OUT
I
OUT
3A VOLTAGE SOURCE
V
IN
I
IN
CURRENT
PROBE
INDUCTOR
Figure 2. Typical Measurement Setup
EVAL-ADP2102
Rev. A | Page 6 of 12
TYPICAL PERFORMANCE CHARACTERISTICS
100
90
80
70
60
50
40
EFFICIENCY (%)
1 10 100 1000
LOAD CURRENT (mA)
V
IN
= 4.2V
V
IN
= 3.6V
V
IN
= 2.7V
06935-004
Figure 3. Efficiency vs. Load Current—ADP2102-1.2-EVALZ (1.2 V Output)
06935-006
CH3 200mA Ω
CH1 5.00V M 100µs A CH3 192mA
3
1
4
T 27.60%
BW
BW
CH4 50.0mV
BW
T
I
LOAD
(0mA - 300mA - 0mA)
V
OUT
(AC)
LX
Figure 4. Load Transient Response for ADP2102-1.2-EVALZ (1.2 V Output)
100
90
80
70
60
EFFICIENCY (%)
1 10 100 1000
LOAD CURRENT (mA)
V
IN
= 4.5V
06935-007
V
IN
= 5.5V
V
IN
= 5.0V
Figure 5. Efficiency vs. Load Current—ADP2102-4-EVALZ (3.3 V Output)
06935-009
CH3 500mA Ω
CH1 5.00V M 100µs A CH2 320V
1
4
3
T 20.60%
BW
CH4 100mV
BW
BW
T
LX
ILOAD (0mA - 500mA - 0mA)
VOUT (AC)
Figure 6. Load Transient Response for ADP2102-4-EVALZ (3.3 V Output)
EVAL-ADP2102
Rev. A | Page 7 of 12
CIRCUIT BOARD LAYOUT RECOMMENDATIONS
Good circuit board layout is essential in obtaining the best
performance from the ADP2102 (see Figure 9, Figure 10, and
Figure 11). Poor circuit layout degrades the output ripple and
regulation, as well as the EMI and electromagnetic compatibility
performance.
Refer to the following guidelines for optimum layout:
• Use separate analog and power ground planes. Connect the
ground reference of sensitive analog circuitry, such as output
voltage divider components, to analog ground. In addition,
connect the ground references of power components, such
as input and output capacitors, to power ground. Connect
both ground planes to the exposed pad of the ADP2102.
• Place the input capacitor as close to the PVIN pin as
possible and connect the other end to the closest power
ground plane.
• For low noise and better transient performance, a filter is
recommended between PVIN and AVIN. Place the 0.1 F,
10 low-pass input filter as close to AVIN as possible,
between the AVIN pin and the PVIN pin; or the AVIN can
be bypassed with a ≥1 pF capacitor to the nearest GND plane.
• Ensure that the high current loops are as short and as wide
as possible. Make the high current path from CIN through
L1, COUT, and the PGND plane back to CIN as short as
possible. To accomplish this, ensure that the input and output
capacitors share a common PGND plane. In addition, make
the high current path from the PGND pin through L1 and
COUT and back to the PGND plane as short as possible.
To do this, ensure that the PGND pin of the ADP2102 is
tied as close as possible to the input and output capacitors on
the PGND plane.
• Place the feedback resistor divider network as close as possible
to the FB pin to prevent noise pickup. Try to minimize the
length of the trace connecting the top of the feedback
resistor divider to the output while keeping away from the
high current traces and the switch node (LX) that can lead
to noise pickup. To reduce noise and parasitic capacitance
pickup, place an analog ground plane on either side of the
FB trace and make it as small as possible.
EVAL-ADP2102
Rev. A | Page 8 of 12
EVALUATION BOARD SCHEMATICS AND ARTWORK
MODE
EN
FB/OUT
AGND
8
7
6
5
1
2
3
4
AVIN
PVIN
LX
PGND
ADP2102
(FIXED)
3
2
1
3
2
1
INTF
JP1
3
2
1
3
2
1
INTF
JP2
CBP
1pF
COUT
4.7µF
CIN
2.2µF
L1
2.2µH
TB3
PGND
TB2
VOUT
TB1
VIN
06935-010
Figure 7. ADP2102-x.x-EVALZ Schematic (Fixed Output Voltage)
MODE
EN
FB/OUT
AGND
8
7
6
5
1
2
3
4
AVIN
PVIN
LX
PGND
ADP2102
(ADJUSTABLE)
3
2
1
3
2
1
INTF
JP1
3
2
1
3
2
1
INTF
JP2
CBP
1pF
CFF
6.8pF
COUT
4.7µF
CIN
2.2µF
L1
2.2µH
TB3
PGND
TB2
VOUT
TB1
VIN
06935-011
R2
R1
Figure 8. ADP2102-x-EVALZ Schematic (Adjustable Output Voltage)
EVAL-ADP2102
Rev. A | Page 9 of 12
VOUT
COUT
PGND
VIN
MODE
EN
FB/OUT
AGND
L1
INDUCTOR
CIN
CBP
ADP2102
06935-012
Figure 9. Recommended Layout of the Top Layer of the ADP2102 Fixed Output Voltage Evaluation Board
VOUT
PGNDMODE
EN
FB/OUT
AGND
VIN
06935-013
Figure 10. Recommended Layout of the Bottom Layer of the ADP2102 Fixed Output Voltage Evaluation Board
06935-014
Figure 11. Recommended Layout of the ADP2102 Adjustable Output Voltage Evaluation Board
EVAL-ADP2102
Rev. A | Page 10 of 12
ORDERING INFORMATION
BILL OF MATERIALS
Table 2. Bill of Materials for ADP2102-x.x-EVALZ (Fixed Output Voltage)
Qty Reference Designator Description Manufacturer Mfg. Part Number
1 CIN Capacitor, MLCC, 2.2 μF, 6.3 V, 0603, X5R, SMD Murata GRM188R60J225K
1 COUT Capacitor, MLCC, 4.7 μF, 6.3 V, 0603, X5R, SMD Murata GRM188R60J475K
1 CBP Capacitor, MLCC, 1 pF, 50 V, 0402, X7R, SMD Murata GJM1554C1H1R0JB01C
1 L1 Inductor, 2.2 μH FDK MIPF2520D2R2
1 U1 Fixed output voltage, 0.6 A, step-down, dc-to-dc
converter
Analog Devices ADP2102-x.x-EVALZ
5 VOUT, VIN, PGND, JP2, JP1 Headers, 0.10 in, single, straight Sullins Electronics or
equivalent
PTC36SAAN
Table 3. Bill of Materials for ADP2102-x-EVALZ (Adjustable Output Voltage)
Qty Reference Designator Description Manufacturer Mfg. Part Number
1 CIN Capacitor, MLCC, 2.2 μF, 6.3 V, 0603, X5R, SMD Murata GRM188R60J225K
1 COUT Capacitor, MLCC, 4.7 μF, 6.3 V, 0603, X5R, SMD Murata GRM188R60J475K
1 CBP Capacitor, MLCC, 1 pF, 50 V, 0402, X7R, SMD Murata GJM1554C1H1R0JB01C
1 R1 Resistor, variable resistance(for example, 316 kΩ for
3.3 V operation), 1%, 0402, SMD
Vishay Dale CRCW04023163F
1 R2 Resistor, variable resistance (for example,100 kΩ for
3.3 V operation), 1%, 0402, SMD
Vishay Dale CRCW04021003F
1 CFF Capacitor, MLCC, 6.8 pF, 25 V, 0402, X7R,SMD Vishay Dale VJ0402A 6R8 KXAA
1 L1 Inductor, 2.2 μH FDK MIPF2520D2R2
1 U1 Adjustable output voltage, 0.6 A, step-down, dc-to-
dc converter
Analog Devices ADP2102-x-EVALZ
5 VOUT, VIN, PGND, JP2, JP1 Headers, 0.10 in, single, straight Sullins Electronics or
equivalent
PTC36SAAN
ORDERING GUIDE
Model Description
ADP2102-0.8-EVALZ1 Evaluation Board (Fixed Output 0.8 V)
ADP2102-1.0-EVALZ1 Evaluation Board (Fixed Output 1.0 V)
ADP2102-1.2-EVALZ1 Evaluation Board (Fixed Output 1.2 V)
ADP2102-1.25-EVALZ1 Evaluation Board (Fixed Output 1.25 V)
ADP2102-1.375EVALZ1 Evaluation Board (Fixed Output 1.375 V)
ADP2102-1.5-EVALZ1 Evaluation Board (Fixed Output 1.5 V)
ADP2102-1.8-EVALZ1 Evaluation Board (Fixed Output 1.8 V)
ADP2102-1.875EVALZ1 Evaluation Board (Fixed Output 1.875 V)
ADP2102-1-EVALZ1 Evaluation Board (Adjustable Output 0.8 V to 1.2 V)
ADP2102-2-EVALZ1 Evaluation Board (Adjustable Output 1.2 V to 1.5 V)
ADP2102-3-EVALZ1 Evaluation Board (Adjustable Output 1.5 V to 1.875 V)
ADP2102-4-EVALZ1 Evaluation Board (Adjustable Output 2.5 V to 3.3 V)
1 Z = RoHS Compliant Part.
ESD CAUTION
EVAL-ADP2102
Rev. A | Page 11 of 12
NOTES
EVAL-ADP2102
Rev. A | Page 12 of 12
NOTES
©2007–2008 Analog Devices, Inc. All rights reserved. Trademarks and
registered trademarks are the property of their respective owners.
EB06935-0-6/08(A)
