ADP2504 Reference Design
Reference Design
PRD1198
FEATURES
Single Buck-Boosted Output: 5 V
Output Current: 600 mA
Input voltage: 3.0-4.2 V
Low Ripple
Accurate constant current limit
DESCRIPTION
This ADP2504 Reference Design uses 3.0 V to 4.2 V for the input voltage. Design criteria are for small size and
low cost. The ripple is less than 10mV. Transient response varies over the load range and is not considered high
priority. The switching frequency is fixed at 2.5 MHz. The output is current limited to 600mA +/-10% and
remains in constant current for Vout down to 2.5 V
Table 1.
User Target Specs, Vout1
Spec
Target
Value
Actual
Value
Units
Vout
5
5
Volts
Iout
0.6
0.6
Amps
Tamb
50
50
degC
Vinmin
3.0
3.0
Volts
Vinmax
4.2
4.2
Volts
Table 2.
Default Design Target Specs, Vout1
Spec
Target
Value
Actual
Value
Units
Vout ripple max
N/A
<0.010
Volts
Ioutstep
N/A
0.6
Apk
Vout step error
N/A
N/A
Volts
MaxHeight
N/A
1.25
mm
Rev. 1
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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 reference designs. Information furnished by Analog
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time without notice. Trademarks and registered trademarks are the property of their respective
owners. Reference designs are not authorized to be used in life support devices or systems.
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Fax: 781.461.3113
©2009 Analog Devices, Inc. All rights reserved.
Reference Design
PRD1198
TABLE OF CONTENTS
Features ......................................................................................................................................................................1
Description .................................................................................................................................................................1
Revision History.........................................................................................................................................................2
Schematic ...................................................................................................................................................................3
Bill of Materials..........................................................................................................................................................3
Simulation results .......................................................................................................................................................5
TABLE OF FIGURES
Figure 1.
Constant Current Limit Buck-Boost Schematic ....................................................................................3
Figure 2.
Bode plot with 10 Ohm load..................................................................................................................5
Figure 3.
Bode plot with 10 Ohm load and 470 uF aluminum output cap ............................................................6
Figure 4.
Bode plot with 7 Ohm load (Vout = 4.2 V, constant current).................................................................7
Figure 5.
Bode plot with 5 Ohm load (Vout = 3 V, constant current)....................................................................8
Figure 6.
Transient with 10 Ohm load and 100 mA dynamic step ........................................................................9
Figure 7.
Transient with 10 Ohm load and 100 mA dynamic step and 470 uF aluminum output cap ................10
REVISION HISTORY
12/24/2009—Revision 0: Initial Version
1/8/2010—Revision 1: Added bode plots for constant current operation
Rev. 1 | Page 2 of 11
Reference Design
PRD1198
SCHEMATIC
Figure 1.
Constant Current Limit Buck-Boost Schematic
L1
Rout
P
Vin
5
Pvin
Cin
1
Sw1 Pgnd Sw2 Vout
Vout
Co
P
Cout
R1
P
R2
P
U1
R3
EN
6
EN
Sync
Vin
Agnd
Cbias
FB
10
C1
D2a
C2
A
Rtop
Rff
Vs
Vs
Vin
U2b
Cff
R4
D2b
Vout
A
D1
Rbot
U2a
Cbyp
A
A
P
A
A
BILL OF MATERIALS
Table 3.
Bill of Materials
Item
#
Des
Mfg
Part Number
Component Specs
1
U1
ADI
ADP2504ACPZ-R7
Current Mode Buck-Boost DC/DC
Regulator
2
U2
ADI
AD8542ARMZ-REEL
1MHz RtoR dual Opamp
3
L1
Coilcraft
LPS4012-152
1.5H, 70 mOhm 4.0x4.0 inductor
4
D1
Diodes
Inc.
1N4448HWT-7
5
D2
Fairchild
6
Cin
TaiyoYuden
Package
Qty
Area
(mm^2)
Height
(mm)
*Cost
LFCSP-10
1
9
.8
1.40
MSOP-8
1
16.5
1.1
0.38
4x4
1
16.0
1.2
0.43
Single 125mA, 100V Signal Diode
SOD-523
1
1.5
0.8
0.056
BAT54CWT1G
Dual Common Cathode, 200mA,
30V Schottkey Diode
SOT-323
1
5.3
1.1
0.041
JMK212 BJ106MG-T
10uF, 6.3V, X5R
0805
1
2.5
1.25
0.025
Rev. 1 | Page 3 of 11
Reference Design
Item
#
PRD1198
Des
Mfg
Part Number
Component Specs
Package
Height
(mm)
*Cost
7
Co
TaiyoYuden
JMK212 BJ106MG-T
10uF, 6.3V, X5R
0805
1
2.5
1.25
0.025
8
Cout
TaiyoYuden
JMK212BJ226MG-T
22uF, 6.3V, X5R
0805
2
5.0
1.25
0.154
9
Cbias
Vishay
10% tolerance
100nF, X7R
0402
1
0.5
0.5
0.010
10
Cbyp
Vishay
10% tolerance
100nF, X7R
0402
1
0.5
0.5
0.010
11
C1
Vishay
10% tolerance
1.0nF, 50V, X7R
0402
1
0.5
0.5
0.010
12
C2
Vishay
10% tolerance
1.0nF, 50V, X7R
0402
1
0.5
0.5
0.010
13
Cff
Vishay
10% tolerance
330pF,50V,C0G
0402
1
0.5
0.5
0.010
14
Rout
Susumu
RL1220S-0R1-G
0.1 Ohm, 2% tol, 0.25W
0805
1
3.2
0.4
0.100
15
Rtop
Vishay
1% tolerance
102 kohm
0402
1
0.5
0.4
0.005
16
Rbot
Vishay
1% tolerance
11.3 kohm
0402
1
0.5
0.4
0.005
17
Rff
Vishay
1% tolerance
30.1 kohm
0402
1
0.5
0.4
0.005
18
R1
Vishay
1% tolerance
10.0 kohm
0402
1
0.5
0.4
0.005
19
R2
Vishay
1% tolerance
10.0 kohm
0402
1
0.5
0.4
0.005
20
R3
Vishay
1% tolerance
82.5 kohm
0402
1
0.5
0.4
0.005
21
R4
Vishay
1% tolerance
82.5 kohm
0402
1
0.5
0.4
0.005
22
67.5
1.25
Total:
Qty
Area
(mm^2)
*BOM prices shown are 1000 piece estimates in US Dollars that should be used for comparison purposes only.
Rev. 1 | Page 4 of 11
2.70
Reference Design
PRD1198
SIMULATION RESULTS
Figure 2.
Bode plot with 10 Ohm load
35.53324k 35.69699k
163.75290
160
140
Phase /
120
100
80
60
59.939404
40
20
0
59.939404
40
Gain / dB
20
0.0000000
0
-20
-40
10
20
40
100 200 400
1k
2k
4k
10k
freq / Hertz
Rev. 1 | Page 5 of 11
20k
40k
REF
A
100k 200k 400k
1M
Reference Design
Figure 3.
PRD1198
Bode plot with 10 Ohm load and 470 uF aluminum output cap
3.569699k 3.631396k
-61.69707
160
140
Phase /
120
100
80
67.786480
60
40
20
0
67.786480
40
Gain / dB
20
0.0000000
0
-20
-40
10
20
40
100 200 400
1k
2k
4k
REF
A
10k
freq / Hertz
Rev. 1 | Page 6 of 11
20k
40k
100k 200k 400k
1M
Reference Design
Figure 4.
PRD1198
Bode plot with 7 Ohm load (Vout = 4.2 V, constant current)
27.38420k 27.49429k
-110.0944
180
160
140
Phase /
120
100
80
60
48.557945
40
20
0
48.557945
40
Gain / dB
20
0
0.0000000
-20
-40
10
20
40
100 200 400
1k
2k
4k
10k 20k 40k
REF
A
freq / Hertz
Rev. 1 | Page 7 of 11
100k 200k 400k
1M
Reference Design
Figure 5.
PRD1198
Bode plot with 5 Ohm load (Vout = 3 V, constant current)
37.48979k 37.50652k
16.722743
160
140
Phase /
120
100
80
60
55.829144
40
20
0
-56.06080
40
Gain / dB
20
-231.660m
0
-20
-40
10
20
40
100 200
400
1k
2k
4k
10k
freq / Hertz
Rev. 1 | Page 8 of 11
20k
40k
REF
A
100k 200k 400k
1M
Reference Design
Figure 6.
PRD1198
Transient with 10 Ohm load and 100 mA dynamic step
5.04
5.02
5
Vout / V
4.98
4.96
4.94
4.92
4.9
4.88
0
0.5
1
1.5
2
2.5
time/mSecs
3
3.5
4
4.5
500uSecs/div
Rev. 1 | Page 9 of 11
Reference Design
Figure 7.
PRD1198
Transient with 10 Ohm load and 100 mA dynamic step and 470 uF aluminum output cap
5.02
5
4.98
Vout / V
4.96
4.94
4.92
4.9
4.88
0
2
4
6
8
time/mSecs
10
12
14
2mSecs/div
Rev. 1 | Page 10 of 11
Reference Design
PRD1198
NOTES
Simulations show the voltage loop is stable with the output caps listed in the BOM and with the addition of
470 uF of additional aluminum output cap. Transient response shows the constant current mode is stable with the
output caps listed in the BOM and with the addition of 470 uF of additional aluminum output cap. The transient
response also shows minimal overshoot when transitioning from one mode to the other.
Simulations also shows that the constant current loop is stable when loaded with 7 Ohms and with 5 Ohms.
©2009 Analog Devices, Inc. All rights reserved.
Trademarks and registered trademarks are the
property of their respective owners. Error! Unknow
Rev. 1 | Page 11 of 11