EVAL-ADP2107:降压DC/DC转换器解决方案评估板 PDF

Evaluation Board for Step-Down DC-to-DC
Converter Solution
EVAL-ADP2107
FEATURES
GENERAL DESCRIPTION
Efficiency > 95%
Input voltage range: 2.7 V to 5.5 V
Output voltage range: 0.8 V to VIN
Maximum output current: 2.0 A
Switching frequency: 1.2 MHz
Quiescent current: 20 μA
Shutdown current: 0.1 μA
Enable/shutdown logic input
Optimized for small ferrite core inductors
Optimized for tiny ceramic input and output capacitors
Programmable soft start with single capacitor
Programmable compensation for optimizing transient
performance
The ADP2107 evaluation board is a complete step-down dc-to-dc
converter solution using the ADP2107 step-down dc-to-dc
converter. It provides a ±1% accurate (±3% over all conditions),
regulated output voltage with load currents up to 2 A. It comes
in two versions: the ADP2107-1.8-EVAL with fixed output
voltage of 1.8 V, and the ADP2107-EVAL with adjustable output
voltage initially set to 2.5 V.
The ADP2107 is a synchronous, step-down dc-to-dc converter
that uses a current-mode pulse width modulation (PWM)
control scheme at medium-to-heavy load currents for high
efficiency, but smoothly transitions to a pulse frequency
modulation (PFM) scheme at light loads to conserve power.
The power switch and synchronous rectifier are integrated for
minimal external part count and high efficiency. The ADP2107
has been optimized for operation with small ferrite core
inductors and tiny ceramic capacitors to deliver the maximum
output power per square inch of the PCB board area.
For more details, see the ADP2107 data sheet.
FUNCTIONAL BLOCK DIAGRAM
ADP2107
EVALUATION BOARD
VIN
J1
R2
GND
ENB
GND
R3
C4
C7
C1
L1
R4 R5
R1
ADP2107
VOUT
C6
C2
C3
VOUT:
ANALOG DEVICES, POWER MANAGEMENT (STP)
06314-001
C5
Figure 1.
Rev. 0
Evaluation boards are only intended for device evaluation and not for production purposes.
Evaluation boards as 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
©2006 Analog Devices, Inc. All rights reserved.
EVAL-ADP2107
TABLE OF CONTENTS
Features .............................................................................................. 1
Changing the Load Transient Response.....................................4
General Description ......................................................................... 1
Measurement Setup...........................................................................5
Functional Block Diagram .............................................................. 1
Typical Performance Characteristics ..............................................6
Using the Evaluation Board............................................................. 3
Ordering Information.......................................................................7
Powering Up the Evaluation Board............................................ 3
Bill of Materials..............................................................................7
Measuring Evaluation Board Performance............................... 3
Ordering Guide .............................................................................9
Modifying the Evaluation Board .................................................... 4
ESD Caution...................................................................................9
Changing the Output Voltage ..................................................... 4
REVISION HISTORY
12/06—Revision 0: Initial Version
Rev. 0 | Page 2 of 12
EVAL-ADP2107
USING THE EVALUATION BOARD
POWERING UP THE EVALUATION BOARD
Turning on the Evaluation Board
The ADP2107 evaluation board is supplied fully assembled and
tested. Before applying power to the evaluation board, follow
the procedures in this section.
Once the power source and the load are connected to the
ADP2107 evaluation board, it can be powered up 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 J1, and check to see if the output voltage rises to
the regulated output voltage (1.8 V for the ADP2107-1.8-EVAL and
2.5 V for the ADP2107-EVAL). If the load is not already enabled,
enable the load, and check that it is drawing the proper current and
that the output voltage maintains voltage regulation.
Jumper J1
Before turning on the ADP2107 evaluation board, make sure
that all the components are present, but Jumper J1 is removed.
Input Power Source
Before connecting the power source to the ADP2107 evaluation
board, make sure that 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 ADP2107 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 that the board is turned off before
connecting 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 the negative (−) load connection to the GND
terminal. If an ammeter is used, connect it in series with the
load; that is, 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 that it is set to the proper current
before powering the ADP2107 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, not the load or power source. If the
voltmeters are not connected directly to the evaluation board,
the measured voltages are 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 the voltmeter positive
terminal (+) 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.
MEASURING EVALUATION BOARD
PERFORMANCE
Measuring Output Voltage Ripple
To observe the output voltage ripple, place an oscilloscope
probe across the output capacitor (C3/C4) 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. In the PWM mode of
operation, the output voltage ripple is small (< 20 mV), but in PFM
mode, the output voltage ripple can be as large as 50 mV.
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 pins with the probe ground at GND.
Set the scope to dc, 2 V/division, and 2 μs/division time base.
The switching waveform should alternate between 0 V and the
approximate input voltage.
Measuring Load Regulation
Load regulation must be tested by increasing the load at the output
and looking at the change in output voltage. To minimize voltage
drop, use short, low-resistance wires, especially for heavy loads.
Measuring Line Regulation
Vary the input voltage and examine the change in the output voltage.
Measuring Efficiency
The efficiency, η, is measured by comparing the input power
with the output power.
η=
VOUT × I OUT
VIN × I IN
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. A current probe can then be used to measure the
current flowing through the current loop, as shown in Figure 2.
Rev. 0 | Page 3 of 12
EVAL-ADP2107
MODIFYING THE EVALUATION BOARD
The ADP2107 evaluation board is supplied fully assembled and
tested for proper operation. It comes in two versions: the
ADP2107-1.8-EVAL with fixed output voltage of 1.8 V and the
ADP2107-EVAL with adjustable output voltage initially set to 2.5 V.
The two most common modifications that can be done to the
evaluation boards are changing the output voltage and changing
the load transient response.
CHANGING THE OUTPUT VOLTAGE
The ADP2107-EVAL output regulation voltage can be changed
by altering its external components. The ADP2107-1.8-EVAL
output regulation voltage is fixed at 1.8 V and cannot be changed.
The ADP2107-EVAL output regulation voltage is set by a
resistive voltage divider consisting of Resistor R4 and Resistor R5.
Resistor R4 corresponds to the RTOP resistor in the ADP2107
data sheet, and Resistor R5 corresponds to the RBOT resistor in
the ADP2107 data sheet. The output regulation voltage is
determined by the equation
⎡ R + RBOT ⎤
VOUT = 0.8 V × ⎢ TOP
⎥
RBOT
⎦
⎣
where:
RTOP is the value of the top resistor of the voltage divider (R4).
RBOT is the value of the bottom resistor of the voltage divider (R5).
VOUT is the output regulation voltage in volts.
To set the output regulation voltage to the desired value, first
determine the value of the bottom resistor, RBOT, by
R BOT =
Note that when the output voltage of the ADP2107-EVAL is
changed, the output capacitors (C3 and C4), the inductor (L1),
and the compensation components (R1 and C6) must be
recalculated and changed according to the Application
Information section in the ADP2107 data sheet to ensure stable
operation.
CHANGING THE LOAD TRANSIENT RESPONSE
The ADP2107 evaluation board load transient response can be
altered by changing the output capacitors (C3 and C4) and the
compensation components (R1 and C6) as explained in the
Output Capacitor section and Loop Compensation section of
the ADP2107 data sheet. By default, the load transient response
of both ADP2107 evaluation boards is set to 5% of the output
voltage for a 1 A load transient.
Consider an example where the load transient response of
ADP2107-1.8-EVAL is changed to 10% of the output voltage for
a 1 A load transient.
First, choose the output capacitors (C3 and C4) based on the load
transient response requirements. The desired load transient
response is 10% overshoot for a 1 A load transient. For this
condition, the % Overshoot for a 1 A Load Transient Response vs.
Output Capacitor × Output Voltage figure in the Output
Capacitor Selection section of the ADP2107 data sheet gives
Output Capacitor × Output Voltage = 25 μC
V FB
⇒ Output Capacitor =
I STRING
where:
VFB is 0.8 V, the internal reference.
ISTRING is the resistor divider string current (20 μA nominally).
Once RBOT is determined, calculate the value of the top resistor,
RTOP, from
RTOP
⎡V
⎡ 2 V − 0.8 V ⎤
− VFB ⎤
R4 = R5 × ⎢ OUT
⎥ = 40 kΩ × ⎢
⎥ = 60 kΩ
⎣ 0.8 V ⎦
⎣ VFB
⎦
Next, taking into account the loss of capacitance due to dc bias
as shown in the % Drop-In Capacitance vs. DC Bias for Ceramic
Capacitors figure in the Output Capacitor Selection section of
the ADP2107 data sheet, let C3 and C4 be two 10 μF X5R MLCC
capacitors (GRM21BR61A106KE19L).
Finally, calculate the compensation resistor and compensation
capacitor as follows:
⎡V
− VFB ⎤
= RBOT ⎢ OUT
⎥
⎣ VFB
⎦
⎛ ( 2 π ) FCROSS
RCOMP = 0.8 ⎜⎜
⎝ G m GCS
For example, to set the output regulation voltage of ADP2107EVAL to 2.0 V, calculate the value of Resistor R4 and Resistor
R5 as shown below.
R5 =
25 μC
≈ 14 μF
1 .8 V
⎞ ⎛ C OUT VOUT
⎟×⎜
⎟ ⎜ V
REF
⎠ ⎝
⎞
⎟⎟
⎠
⎞ ⎛ 14 μF × 1.8 V ⎞
⎛
( 2 π ) × 80 kHz
⎟⎟ = 70 kΩ
⎟⎟ × ⎜⎜
= 0.8 ⎜⎜
50
μA
/
V
×
3
.
625
A
/
V
0 .8 V
⎠
⎠ ⎝
⎝
VFB
0.8 V
=
= 40 kΩ
I STRING 20 μA
CCOMP =
2
2
=
= 120 pF
πFCROSS RCOMP π × 80 kHz × 70 kΩ
Therefore, choose the compensation resistor to be 70 kΩ and
the compensation capacitor to be 120 pF.
Rev. 0 | Page 4 of 12
EVAL-ADP2107
MEASUREMENT SETUP
ELECTRONIC LOAD
VOLTMETER
3A VOLTAGE SOURCE
VIN
IIN
VOUT
IOUT
J1
R2
GND
ENABLE
VIN
GND
PROBE OUTPUT
VOLTAGE ACROSS
OUTPUT CAPACITOR
R3
C4
C7
C1
R4
ADP2107
L1
R5
VOUT
R1
C6
C5
C2
CURRENT
PROBE
C3
INDUCTOR
OSCILLOSCOPE
1V SEP
1V SEP AT NORW
OFF
0V H
0V V
EVE
OFF
0V H
0V V
VD 1S DIV
VD 1S DIV
VPOS
NVERT
OUTPUT
VOLTAGE
WAVEFORM
mV
V
mV
DVA DVA ADD
LX NODE
WAVEFORM
Figure 2. Typical Measurement Setup
Rev. 0 | Page 5 of 12
CH
INDUCTOR
CURRENT
WAVEFORM
06314-010
V
EVAL-ADP2107
TYPICAL PERFORMANCE CHARACTERISTICS
100
100
VIN = 3.6V
95
VIN = 2.7V
90
85
VIN = 4.2V
EFFICIENCY (%)
80
VIN = 5.5V
75
70
VIN = 5.5V
VIN = 4.2V
80
75
70
65
65
60
60
55
1
10
100
06314-004
INDUCTOR: D62LCB, 1.5µH
DCR: 21mΩ
TA = 25°C
50
10000
1000
INDUCTOR: D62LCB, 2.0μH
DCR: 28mΩ
TA = 25°C
55
1
10
100
06314-007
EFFICIENCY (%)
VIN = 3.6V
90
85
50
VIN = 3.0V
95
10000
1000
LOAD CURRENT (mA)
LOAD CURRENT (mA)
Figure 6. Efficiency—ADP2107-EVAL (2.5 V Output)
Figure 3. Efficiency—ADP2107-1.8-EVAL (1.8 V Output)
LX NODE (SWITCH NODE)
LX NODE
(SWITCH NODE)
3
3
1
1
OUTPUT VOLTAGE (AC-COUPLED)
OUTPUT VOLTAGE (AC-COUPLED)
CH4 200mAΩ
M 2µs
T 6%
A CH3
4
CH1 20mV
CH3 2V
3.88V
CH4 1AΩ
M 1µs
T 17.4%
A CH3
3.88V
Figure 7. PWM Mode of Operation at Medium/Heavy Load (1.5 A)
Figure 4. PFM Mode of Operation at Light Load (10 mA)
OUTPUT CURRENT
3
2
OUTPUT CURRENT
2
CH2 LOW
–108mV
LX (SWITCH) NODE VOLTAGE
CH2 100mV
M 10µs
T 10.4%
A CH2
OUTPUT VOLTAGE
(AC-COUPLED)
1
06314-006
1
CH1 2V
CH3 1A
CH2 LOW
–140mV
OUTPUT VOLTAGE (AC-COUPLED)
06314-009
3
06314-008
INDUCTOR CURRENT
CH1 50mV
CH3 2V
INDUCTOR CURRENT
06314-005
4
LX (SWITCH) NODE VOLTAGE
CH1 2V
CH3 1A
100mV
Figure 5. 1 A Load Transient Response for ADP2107-1.8-EVAL
CH2 100mV
M 10µs
T 20.20%
A CH2
100mV
Figure 8. 1 A Load Transient Response for ADP2107-EVAL
with VOUT Set to 2.5 V
Rev. 0 | Page 6 of 12
EVAL-ADP2107
ORDERING INFORMATION
BILL OF MATERIALS
Table 1. Bill of Materials for ADP2107-1.8-EVAL with VOUT Set to 1.8 V
Ref. Des.
Ref. Name 1
Quantity
Manufacturer
Mfg. Part Number
Capacitor, MLCC, 10 μF, 10 V,
0805, X5R, SMD
Capacitor, MLCC, 22 μF, 6.3 V,
0805, X5R, SMD
Capacitor, MLCC, 1 nF, 16 V,
0603, X7R, SMD
C1, C2
CIN1, CIN2
2
Murata
GRM21BR61A106KE19L
C3, C4
COUT
2
Murata
GRM21BR60J226ME39L
C5
CSS
1
Vishay Vitramon or
equivalent
VJ0603Y102KXJA
Capacitor, MLCC, 68 pF, 50 V,
0603, NPO
Capacitor, MLCC, 0.1 μF, 25 V,
0603, X7R, SMD
Resistor, 140 kΩ, 1%, 0603, SMD
Resistor, 100 kΩ, 1%, 0603, SMD
C6
CCOMP
1
VJ0603Y680KXJA
C7
1
1
1
Resistor, 10 Ω, 1%, 0603, SMD
R3
IN (filter
capacitor)
RCOMP
EN (pull
down)
IN (filter
resistor)
Vishay Vitramon or
equivalent
Vishay Vitramon or
equivalent
Vishay Dale or equivalent
Vishay Dale or equivalent
1
Vishay Dale or equivalent
CRCW060310R0FRT1
Resistor, 0 Ω, 1%, 0603, SMD
Bottom Resistor of Voltage
Divider
Inductor 1.5 μH, 6.3 mm ×
6.2 mm × 2.0 mm
1.8 V, 2 A, Step-Down DC-to-DC
Converter
R4
R5
1
Vishay Dale or equivalent
CRCW06030000ZSSF
No stuff
1
Toko
D62LCB—1R5M
U1
1
Analog Devices, Inc.
ADP2107-1.8
Headers, 0.100, Single, Straight
VOUT, VIN,
GND, GND,
J1, EN
6
Sullins Electric or
equivalent
S1012-36-ND PTC36SAAN
R1
R2
L1
L
VJ0603Y104KXXA
CRCW06031403FRT1
CRCW06031003FRT1
Refer to the Typical Applications Circuit for Fixed Output Voltage Options figure in the ADP2107 data sheet.
V
C7
R3 IN
0.1µF 10Ω
VIN
J1
16
15
14
13
FB
GND
IN
PWIN1
1
EN
2
GND3
EN
R2
100kΩ
C1
10µF
FB
U1
ADP2107
1
LX1 10
PWIN2 9
COMP SS AGND PADDLE NC
5
OUTPUT VOLTAGE = 2.5V
PGND 11
GND1
4
GND
LX2 12
GND2
3
INPUT VOLTAGE: 2.7V TO 5.5V
VIN
6
7
17
C5
1nF
2
VIN
C2
10µF
8
OUT
OUTPUT VOLTAGE: 1.8V
C3
22µF
C4
22µF
R4
0kΩ
VOUT
GND
R5
NS
R1
140kΩ
C6
68pF
L1
1.5µH
NC = NO CONNECT
Figure 9. Evaluation Board Schematic of ADP2107-1.8-EVAL with VOUT = 1.8 V
Rev. 0 | Page 7 of 12
06314-002
1
Description
EVAL-ADP2107
Table 2. Bill of Materials for ADP2107-EVAL with VOUT Set to 2.5 V
Ref. Des.
C1, C2
Ref. Name1
CIN1, CIN2
QTY
2
Manufacturer
Murata
Mfg. Part Number
GRM21BR61A106KE19L
C3
COUT
1
Murata
GRM21BR60J226ME39L
C4
COUT
1
Murata
GRM21BR61A106KE19L
Capacitor, MLCC, 1 nF, 16 V,
0603, X7R, SMD
Capacitor, MLCC, 68 pF, 50 V,
0603, NPO
Capacitor, MLCC, 0.1 μF, 25 V,
0603, X7R, SMD
Resistor, 140 kΩ, 1%, 0603, SMD
Resistor, 100 kΩ, 1%, 0603, SMD
Resistor, 10 Ω, 1%, 0603, SMD
C5
CSS
1
VJ0603Y102KXJA
C6
CCOMP
1
C7
1
1
1
1
Resistor, 87.6 kΩ, 0.5%, 0603,
SMD
Resistor, 41.2 kΩ, 0.1%, 0603,
SMD
Inductor 2.0 μH, 6.3 mm x
6.2 mm x 2.0 mm
R4
IN (filter
capacitor)
RCOMP
EN (pull down)
IN (filter
resistor)
RTOP
Vishay Vitramon or
equivalent
Vishay Vitramon or
equivalent
Vishay Vitramon or
equivalent
Vishay Dale or equivalent
Vishay Dale or equivalent
Vishay Dale or equivalent
1
Vishay Dale or equivalent
TNPW060387K6DHTA
R5
RBOT
1
Vishay Dale or equivalent
TNPW060341K2BEEN
L1
L
1
Toko
D62LCB-2R0M
2 A Step-Down DC-to-DC
Converter with Adjustable
Output
Headers, 0.100, Single, Straight
U1
1
Analog Devices, Inc.
ADP2107-ADJ
VOUT, VIN, GND,
GND, J1, EN
6
Sullins Electric or equivalent
S1012-36-ND PTC36SAAN
R1
R2
R3
VJ0603Y680KXJA
VJ0603Y104KXXA
CRCW06031403FRT1
CRCW06031003FRT1
CRCW060310R0FRT1
Refer to the Typical Applications Circuit for Adjustable Output Voltage Option figure in the ADP2107 data sheet.
V
C7
R3 IN
0.1µF 10Ω
VIN
16
15
14
13
FB
GND
IN
PWIN1
1
EN
2
GND3
EN
R2
100kΩ
C1
10µF
FB
J1
U1
ADP2107
PGND 11
PWIN2 9
COMP SS AGND PADDLE NC
5
1
LX1 10
GND1
4
GND
LX2 12
GND2
3
INPUT VOLTAGE: 2.7V TO 5.5V
VIN
6
7
17
C5
1nF
2
VIN
C2
10µF
8
FB
OUTPUT VOLTAGE: 2.5V
C3
22µF
R4
87.6kΩ
C4
10µF
VOUT
GND
R5
41.2kΩ
R1
140kΩ
C6
68pF
L1
2.0µH
NC = NO CONNECT
06314-003
1
Description
Capacitor, MLCC, 10 μF, 10 V,
0805, X5R, SMD
Capacitor, MLCC, 22 μF, 6.3 V,
0805, X5R, SMD
Capacitor, MLCC, 10 μF, 10 V,
0805, X5R, SMD
Figure 10. Evaluation Board Schematic for ADP2107-EVAL with Adjustable VOUT Initially Set to 2.5 V
Rev. 0 | Page 8 of 12
EVAL-ADP2107
ESD CAUTION
ORDERING GUIDE
Model
ADP2107-1.8-EVAL
ADP2107-EVAL
Description
Evaluation Board
Evaluation Board
Rev. 0 | Page 9 of 12
EVAL-ADP2107
NOTES
Rev. 0 | Page 10 of 12
EVAL-ADP2107
NOTES
Rev. 0 | Page 11 of 12
EVAL-ADP2107
NOTES
©2006 Analog Devices, Inc. All rights reserved. Trademarks and
registered trademarks are the property of their respective owners.
EB06314-0-12/06(0)
T
T
Rev. 0 | Page 12 of 12