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Table of Contents
User’s Guide
LM2738 Step-Down Converter Evaluation Module User's
Guide
Table of Contents
1 Introduction.............................................................................................................................................................................2
2 Operating Conditions............................................................................................................................................................. 2
3 PCB Layout - WSON............................................................................................................................................................... 4
4 PCB Layout - MSOP-PowerPAD............................................................................................................................................ 6
5 Additional Circuit Configuration Schematics...................................................................................................................... 8
6 Revision History....................................................................................................................................................................11
List of Figures
Figure 2-1. LM2738 Demo Board Schematic - VBOOST Derived from VOUT = 3.3 V, VIN = 12 V.................................................. 2
Figure 2-2. Efficiency vs Load Current - VIN = 12 V, VOUT = 3.3 V.............................................................................................. 2
Figure 3-1. Top Layer...................................................................................................................................................................4
Figure 3-2. Internal Plane - Layer 2 (GND)..................................................................................................................................4
Figure 3-3. Internal Plane - Layer 3 (GND)..................................................................................................................................5
Figure 3-4. Bottom Layer............................................................................................................................................................. 5
Figure 4-1. Top Layer...................................................................................................................................................................6
Figure 4-2. Internal Plane - Layer 2 (GND)..................................................................................................................................6
Figure 4-3. Internal Plane - Layer 3 (GND)..................................................................................................................................7
Figure 4-4. Bottom Layer............................................................................................................................................................. 7
Figure 5-1. VBOOST Derived from VIN = 5 V, for VOUT = 1.5 V...................................................................................................... 8
Figure 5-2. VBOOST Derived from VSHUNT Coming from VIN = 18 V, VOUT = 1.5 V.......................................................................9
Figure 5-3. VBOOST Derived from Series Zener Diode from VIN = 15 V, VOUT = 1.5 V............................................................... 10
Figure 5-4. VBOOST Derived from Series Zener Diode from VOUT = 9 V, VIN = 15 V.................................................................. 11
List of Tables
Table 2-1. Bill of Materials X-Version (1.6 MHz).......................................................................................................................... 3
Table 2-2. Bill of Materials Y-Version (550 kHz)...........................................................................................................................3
Table 5-1. Bill of Materials X-Version (1.6 MHz).......................................................................................................................... 8
Table 5-2. Bill of Materials Y-Version (550 kHz)...........................................................................................................................8
Table 5-3. Bill of Materials X-Version (1.6 MHz).......................................................................................................................... 9
Table 5-4. Bill of Materials Y-Version (550 kHz)...........................................................................................................................9
Table 5-5. Bill of Materials X-Version (1.6 MHz)........................................................................................................................ 10
Table 5-6. Bill of Materials Y-Version (550 kHz).........................................................................................................................10
Table 5-7. Bill of Materials X-Version (1.6 MHz).........................................................................................................................11
Table 5-8. Bill of Materials Y-Version (550 kHz)......................................................................................................................... 11
Trademarks
All trademarks are the property of their respective owners.
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1
Introduction
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1 Introduction
The LM2738 demo board is configured to convert 12-V input to 3.3-V output at 1.5-A load current using
the LM2738X 1.6-MHz or the LM2738Y 550-kHz step down DC-DC regulator. The tiny low profile MSOPPowerPAD-8 and WSON-8 packages allows the demo board to be manufactured using just over one square inch
of a 4-layer printed circuit board.
The circuit is configured with the boost diode connected to VOUT, and according to the data sheet, VOUT must
not exceed the maximum operating limit of 5.5 V + VfD2 using this configuration. This makes sure that the
voltage between the boost and SW pins, VBOOST–VSW, does not exceed 5.5 V for proper operation. Please
see the LM2738 550kHz/1.6MHz 1.5A Step-Down DC-DC Switching Regulator data sheet for more information
regarding this requirement.
A bill of materials describes the parts used on this demo board. A schematic and layout have also been
included along with measured performance characteristics. The schematics at the end of this document show
how to re-configure this demo board for various input and output conditions as discussed in the LM2738 550kHz/
1.6MHz 1.5A Step-Down DC-DC Switching Regulator data sheet. Short or leave open the indicated connection
as indicated in the schematics. The above restrictions for the input voltage are valid only for the demo board as
shipped with the demo board schematic (see Figure 2-1).
2 Operating Conditions
•
•
•
VIN = 12 V
VO = 3.3 V
IO = 1.5 A
Figure 2-1. LM2738 Demo Board Schematic - VBOOST Derived from VOUT = 3.3 V, VIN = 12 V
Figure 2-2. Efficiency vs Load Current - VIN = 12 V, VOUT = 3.3 V
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Operating Conditions
Table 2-1. Bill of Materials X-Version (1.6 MHz)
Part ID
Part Value
Manufacturer
Part Number
Package Type
C1, Input Cap
10 µF, 25 V, X7R
TDK
C3216X5R1E106
1206
C2, C5, Output Cap
22 µF, 10 V, X5R
TDK
C3216X5R1A226
1206
C3 (Boost Cap), C4
0.1 µF
TDK
C2012X7R1A104
0805
D2, Boost Diode
1 VF at 100-mA Diode
Diodes, Inc.
BAT54WS-TP
SOD-323
R2, R3
10 kΩ, 1%
Vishay
CRCW12061002F
0805
LM2738
WSON-8
U1
1.5-A Buck Regulator
Texas Instruments
LM2738
MSOP-PowerPAD-8
D1, Catch Diode
0.34-VF Schottky, 1.5 A, 30
VR
Toshiba
CRS08
-
L1
5.0 µH, 2.9 A
Coilcraft
MSS7341-502NL
-
R1
31.6 kΩ, 1%
Vishay
CRCW12063162F
0805
R5
0Ω
Vishay
CRCW12060R00F
0805
D4, R4
Open or No Load
Part ID
Part Value
Manufacturer
Part Number
Package Type
C1, Input Cap
10 µF, 25 V, X7R
TDK
C3216X5R1E106
1206
C2, C5, Output Cap
22 µF, 10 V, X5R
TDK
C3216X5R1A226
1206
Table 2-2. Bill of Materials Y-Version (550 kHz)
C3 (Boost Cap), C4
0.1 µF
TDK
C2012X7R1A104
0805
D2, Boost Diode
1 VF at 100 mA Diode
Diodes, Inc.
BAT54WS-TP
SOD-323
R2, R3
10 kΩ, 1%
Vishay
CRCW12061002F
0805
LM2738
WSON-8
U1
1.5-A Buck Regulator
Texas Instruments
LM2738
MSOP-PowerPAD-8
D1, Catch Diode
0.34 VF Schottky, 1.5 A, 30
VR
Toshiba
CRS08
-
L1
10.0 µH, 2.0 A
Coilcraft
MSS7341-103NL
-
R1
31.6 kΩ, 1%
Vishay
CRCW12063162F
0805
R5
0Ω
Vishay
CRCW12060R00F
0805
D4, R4
Open or No Load
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3
PCB Layout - WSON
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3 PCB Layout - WSON
Figure 3-1. Top Layer
Figure 3-2. Internal Plane - Layer 2 (GND)
4
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PCB Layout - WSON
Figure 3-3. Internal Plane - Layer 3 (GND)
Figure 3-4. Bottom Layer
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5
PCB Layout - MSOP-PowerPAD
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4 PCB Layout - MSOP-PowerPAD
Figure 4-1. Top Layer
Figure 4-2. Internal Plane - Layer 2 (GND)
6
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PCB Layout - MSOP-PowerPAD
Figure 4-3. Internal Plane - Layer 3 (GND)
Figure 4-4. Bottom Layer
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Additional Circuit Configuration Schematics
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5 Additional Circuit Configuration Schematics
Figure 5-1. VBOOST Derived from VIN = 5 V, for VOUT = 1.5 V
Table 5-1. Bill of Materials X-Version (1.6 MHz)
Part ID
Part Value
Manufacturer
Part Number
Package Type
C1, Input Cap
10 µF, 25 V, X7R
C2, Output Cap
22 µF, 6.3 V, X5R
TDK
C3216X5R1E106
1206
TDK
C3216X5R0J2266
1206
C3 (Boost Cap), C4
0.1 µF
TDK
C2012X7R1A104
0805
D2, Boost Diode
1 VF at 100-mA Diode
Diodes, Inc.
BAT54WS-TP
SOD-323
R2, R3
10 kΩ, 1%
Vishay
CRCW12061002F
0805
LM2738
WSON-8
LM2738
MSOP-PowerPAD-8
U1
1.5-A Buck Regulator
Texas Instruments
D1, Catch Diode
0.34 VF Schottky, 1.5 A, 30 V
Toshiba
CRS08
-
L1
2.2 µH, 1.9A
Coilcraft
MSS5131-222ML
-
R1
8.87 kΩ, 1%
Vishay
CRCW12068871F
0805
R4
0Ω
Vishay
CRCW12060R00F
0805
D4, R5, C5
Open or No Load
Part ID
Part Value
Manufacturer
Part Number
Package Type
C1, Input Cap
10 µF, 25 V, X7R
TDK
C3216X5R1E106
1206
C2, C5, Output Caps
22 µF, 6.3 V, X5R
TDK
C3216X5R0J226
1206
C3 (Boost Cap), C4
0.1 µF
TDK
C2012X7R1A104
0805
D2, Boost Diode
1 VF at 100-mA Diode
Diodes, Inc.
BAT54WS-TP
SOD-323
R2, R3
10 kΩ, 1%
Vishay
CRCW12061002F
0805
U1
1.5-A Buck Regulator
Texas Instruments
D1, Catch Diode
0.34 VF Schottky ,1.5 A, 30
V
L1
Table 5-2. Bill of Materials Y-Version (550 kHz)
8
LM2738
WSON-8
LM2738
MSOP-PowerPAD-8
Toshiba
CRS08
-
6.2 µH, 2.5 A
Coilcraft
MSS7341-622NL
-
R1
8.87 kΩ, 1%
Vishay
CRCW12068871F
0805
R4
0Ω
Vishay
CRCW12060R00F
0805
D4, R5
Open or No Load
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Additional Circuit Configuration Schematics
Figure 5-2. VBOOST Derived from VSHUNT Coming from VIN = 18 V, VOUT = 1.5 V
Table 5-3. Bill of Materials X-Version (1.6 MHz)
Part ID
Part Value
Manufacturer
Part Number
Package Type
C1, Input Cap
10 µF, 25V, X7R
TDK
C3216X5R1E106
1206
C2, C5, Output Caps
22 µF, 6.3V, X5R
TDK
C3216X5R0J226
1206
C3 (Boost Cap), C4
0.1 µF
TDK
C2012X7R1A104
0805
D2, Boost Diode
1 VF at 100-mA Diode
Diodes, Inc.
BAT54WS-TP
SOD-323
D4, Zeneer
5.1 V, 200 mW
Diodes, Inc.
BZX84C5V1W
SOT-323
R2, R3
10 kΩ, 1%
Vishay
CRCW12061002F
0805
LM2738
WSON-8
U1
1.5-A Buck Regulator
Texas Instruments
LM2738
MSOP-PowerPAD-8
D1, Catch Diode
0.34 VF Schottky, 1.5 A, 30 V
Toshiba
CRS08
-
L1
2.7 µH, 1.76 A
TDK
VLCF5020T-2R7N1R7
-
R1
8.87 kΩ, 1%
Vishay
CRCW12068871F
0805
R4
4.12 kΩ, 1%
Vishay
CRCW12064121F
0805
R5
Open or No Load
Part ID
Part Value
Manufacturer
Part Number
Package Type
C1, Input Cap
10 µF, 25 V, X7R
TDK
C3216X5R1E106
1206
C2, C5, Output Caps
47 µF, 6.3 V, X5R
TDK
C3216X5R0J476
1206
Table 5-4. Bill of Materials Y-Version (550 kHz)
C3 (Boost Cap), C4
0.1 µF
TDK
C2012X7R1A104
0805
D2, Boost Diode
1 VF at 100-mA Diode
Diodes, Inc.
BAT54WS-TP
SOD-323
D4, Zeneer
5.1 V, 200 mW
Diodes, Inc.
BZX84C5V1W
SOT-323
R2, R3
10 kΩ, 1%
Vishay
CRCW12061002F
0805
U1
1.5-A Buck Regulator
Texas Instruments
D1, Catch Diode
0.34 VF Schottky, 1.5 A, 30 V
L1
8.7 µH, 2.2 A
R1
8.87 kΩ, 1%
R4
4.21 kΩ, 1%
R5
Open or No Load
LM2738
WSON-8
LM2738
MSOP-PowerPAD-8
Toshiba
CRS08
-
Coilcraft
MSS7341-872NL
-
Vishay
CRCW12068871F
0805
Vishay
CRCW12064211F
0805
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Additional Circuit Configuration Schematics
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Figure 5-3. VBOOST Derived from Series Zener Diode from VIN = 15 V, VOUT = 1.5 V
Table 5-5. Bill of Materials X-Version (1.6 MHz)
Part ID
Part Value
Manufacturer
Part Number
Package Type
C1, Input Cap
10 µF, 25 V, X7R
TDK
C3216X5R1E106
1206
C2, C5, Output Caps
22 µF, 6.3 V, X5R
TDK
C3216X5R0J226
1206
C3 (Boost Cap)
0.1 µF
TDK
C2012X7R1A104
0805
D2, Boost Diode
1 VF at 100-mA Diode
Diodes, Inc.
BAT54WS-TP
SOD-323
R2, R3
10 kΩ, 1%
Vishay
CRCW12061002F
0805
LM2738
WSON-8
LM2738
MSOP-PowerPAD-8
U1
1.5-A Buck Regulator
Texas Instruments
D1, Catch Diode
0.34 VF Schottky, 1.5 A, 30 V
Toshiba
CRS08
-
L1
3.3 µH, 3.5 A
Coilcraft
MSS7341-332NL
-
R1
8.87 kΩ, 1%
Vishay
CRCW12068871F
0805
R4
11 V, 200 mW, Zener
Vishay
BZX384C11-V
SOD-323
D4, R5, C4
Open or No Load
Part ID
Part Value
Manufacturer
Part Number
Package Type
C1, Input Cap
10 µF, 25 V, X7R
TDK
C3216X5R1E106
1206
C2, C5, Output Caps
47 µF, 6.3 V, X5R
TDK
C3216X5R0J476
1206
C3 (Boost Cap)
0.1 µF
TDK
C2012X7R1A104
0805
D2, Boost Diode
1 VF at 100-mA Diode
Diodes, Inc.
BAT54WS-TP
SOD-323
R2, R3
10 kΩ, 1%
Vishay
CRCW12061002F
0805
U1
1.5-A Buck Regulator
Texas Instruments
D1, Catch Diode
0.34 VF Schottky, 1.5 A, 30 V
L1
8.7 µH, 2.2 A
R1
8.87 kΩ, 1%
Vishay
CRCW12068871F
0805
R4
11 V, 200 mW, Zener
Vishay
BZX384C11-V
SOD-323
D4, R5, C4
Open or No Load
Table 5-6. Bill of Materials Y-Version (550 kHz)
10
LM2738 Step-Down Converter Evaluation Module User's Guide
LM2738
WSON-8
LM2738
MSOP-PowerPAD-8
Toshiba
CRS08
-
Coilcraft
MSS7341-872NL
-
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Revision History
Figure 5-4. VBOOST Derived from Series Zener Diode from VOUT = 9 V, VIN = 15 V
Table 5-7. Bill of Materials X-Version (1.6 MHz)
Part ID
Part Value
Manufacturer
Part Number
Package Type
C1, Input Cap
10 µF, 25 V, X7R
TDK
C3216X5R1E106
1206
C2, Output Cap
22 µF, 10 V, X5R
TDK
C3216X5R1A226
1206
C3 (Boost Cap), C4
0.1 µF
TDK
C2012X7R1A104
0805
D2, Boost Diode
1 VF at 100-mA Diode
Diodes, Inc.
BAT54WS-TP
SOD-323
R2, R3
10 kΩ, 1%
Vishay
CRCW12061002F
0805
LM2738
WSON-8
LM2738
MSOP-PowerPAD-8
U1
1.5-A Buck Regulator
Texas Instruments
D1, Catch Diode
0.34 VF Schottky, 1.5 A, 30 V
Toshiba
CRS08
-
L1
6.2 µH, 2.5 A
Coilcraft
MSS7341-622NL
-
R1
102 kΩ, 1%
Vishay
CRCW1206123F
0805
R5
4.3 V, 200 mW, Zener
Vishay
BZX384C4V3-V
SOD-323
D4, R4
Open or No Load
Part ID
Part Value
Manufacturer
Part Number
Package Type
C1, Input Cap
10 µF, 25 V, X7R
TDK
C3216X5R1E106
1206
Table 5-8. Bill of Materials Y-Version (550 kHz)
C2, Output Cap
22 µF, 10 V, X5R
TDK
C3216X5R1A226
1206
C3 (Boost Cap), C4
0.1 µF
TDK
C2012X7R1A104
0805
D2, Boost Diode
1 VF at 100-mA Diode
Diodes, Inc.
BAT54WS-TP
SOD-323
R2, R3
10 kΩ, 1%
Vishay
CRCW12061002F
0805
U1
1.5-A Buck Regulator
Texas Instruments
D1, Catch Diode
0.34 VF Schottky, 1.5 A, 30V
L1
5.0 µH, 2.9 A
R1
102 kΩ, 1%
Vishay
CRCW12061023F
0805
R5
4.3 V, 200 mW, Zener
Vishay
BZX384C4V3-V
SOD-323
D4, R4
Open or No Load
LM2738
WSON-8
LM2738
MSOP-PowerPAD-8
Toshiba
CRS08
-
Coilcraft
MSS7341-502NL
-
6 Revision History
NOTE: Page numbers for previous revisions may differ from page numbers in the current version.
Changes from Revision A (April 2013) to Revision B (December 2021)
Page
• Updated the numbering format for tables, figures, and cross-references throughout the document. ................2
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Revision History
•
•
12
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Updated the user's guide title............................................................................................................................. 2
Edited user's guide for clarity..............................................................................................................................2
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