Texas LM2736 User manual

EN
BOOST
SW
FB
GND
VOUT
L1
R1
R2
D1
D2
D3
R3
C1 R5
R4
GND GND
C4
C3
C2
VIN
VIN
VEN
User's Guide
SNVA135A–October 2005–Revised April 2013
AN-1418 LM2736 Evaluation Board
1 Introduction
The LM2736 demo board is configured to convert 5V input to 1.5V output at 750 mA load current using
the LM2736X 1.6 MHz or the LM2736Y 550 kHz step down DC-DC regulator. The tiny low profile thin
SOT23 package allows the demo board to be manufactured using less than 1 square inch of a 4-layer
printed circuit board.
The circuit is configured with the boost diode connected to VIN, and according to the datasheet, VIN must
not exceed the maximum operating limit of 5.5V + VfD2 using this configuration. This will ensure that the
voltage between the Boost and SW pins, VBOOST - VSW, does not exceed 5.5V for proper operation. For
more information regarding this requirement, see the LM2736 Thin SOT 750mA Load Step-Down DC-DC
Regulator Data Sheet (SNVS316).
A bill of materials below describes the parts used on this demo board. A schematic and layout have also
been included below 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 LM2736 datasheet. 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 below.
2 Operating Conditions
VIN = 5V
VO= 1.5V
IO= 750 mA
Figure 1. LM2736 Demo Board Schematic
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Operating Conditions www.ti.com
Figure 2. Efficiency vs Load Current
Table 1. Bill of Materials (BOM) X-Version
Part ID Part Value Manufacturer Part Number Package Type
C1, Input Cap 4.7 µF, 10V, X5R Murata GRM42-6X5R475K10 1206
C2, Output Cap 10 µF, 6.3V, X5R Murata GRM42-6X5R106K6.3 1206
C3, Boost Cap 0.01 µF Vishay VJ1206Y103KXXA 1206
D2, Boost Diode 1Vf@ 50 mA Diode Diodes, Inc. 1N4148W SOD-123
R2 10 kΩ, 1% Vishay CRCW12061002F 1206
U1 750 mA Buck Regulator Texas Instruments LM2736 Thin SOT23-6
D1, Catch Diode 0.34VfSchottky 1A, 20VRInternational Rectifier MBRA120 SMA
L1 4.7 µH, 1.6A, 28 mΩTDK SLF6028T-4R7M1R6 6028
R1 2 kΩ, 1% Vishay CRCW12062001F 1206
R3 0ΩVishay CRCW12060000F 1206
R5 50 kΩ, 1% Vishay CRCW08055002F 0805
D3, C4, R4 Open
Table 2. Bill of Materials (BOM) Y-Version
Part ID Part Value Manufacturer Part Number Package Type
C1, Input Cap 10 µF, 10V, X5R Murata GRM42-6X5R106K10 1206
C2, Output Cap 10 µF, 6.3V, X5R Murata GRM42-6X5R106K6.3 1206
C3, Boost Cap 0.01 µF Vishay VJ1206Y103KXXA 1206
D2, Boost Diode 1Vf@ 50 mA Diode Diodes, Inc. 1N4148W SOD-123
R2 10 kΩ, 1% Vishay CRCW12061002F 1206
U1 750 mA Buck Regulator Texas Instruments LM2736 Thin SOT23-6
D1, Catch Diode 0.34VfSchottky 1A, 20VRInternational Rectifier MBRA120 SMA
L1 10 µH, 1.3A, 53 mΩTDK SLF6028T-100M1R3 6028
R1 2 kΩ, 1% Vishay CRCW12062001F 1206
R3 0ΩVishay CRCW12060000F 1206
R5 50 kΩ, 1% Vishay CRCW08055002F 0805
D3, C4, R4 Open
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www.ti.com PCB Layout
3 PCB Layout
Figure 3. Top Layer
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PCB Layout www.ti.com
Figure 4. Internal Plane 1 (GND)
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www.ti.com PCB Layout
Figure 5. Internal Plane 2 (VIN)
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PCB Layout www.ti.com
Figure 6. Bottom Layer
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VIN VIN
EN
BOOST
SW
FB
GND
VOUT
C3 L1
C2
R1
R2
D1
D2
D3
C4
R3
C1 R5
R4
VEN
GND GND
VIN VIN
EN
BOOST
SW
FB
GND
VOUT
C3 L1
C2
R1
R2
D1
D2
D3
C4
R3
C1 R5
R4
VEN
GND GND
www.ti.com Additional Circuit Configuration Schematics
4 Additional Circuit Configuration Schematics
Figure 7. VBOOST Derived From VOUT
Figure 8. VBOOST Derived From VSHUNT
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VIN VIN
EN
BOOST
SW
FB
GND
VOUT
C3 L1
C2
R1
R2
D1
D2
D3
C4
R3
C1 R5
R4
VEN
GND GND
VIN VIN
EN
BOOST
SW
FB
GND
VOUT
C3 L1
C2
R1
R2
D1
D2
D3
C4
R3
C1 R5
R4
VEN
GND GND
Additional Circuit Configuration Schematics www.ti.com
Figure 9. VBOOST Derived From Series Zener Diode (VIN)
Figure 10. VBOOST Derived From Series Zener Diode (VOUT)
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