Texas Instruments LMR51450 EVM User manual

User’s Guide
LMR51450 EVM
ABSTRACT
The LMR51450 evaluation module (EVM) is designed to help customers evaluate the performance of the
LMR51450 synchronous step-down voltage converter. This EVM implements the LMR51450 in a 12-pin WSON
package, as shown in Table 1-1. The EVM is capable of delivering 5 V or 3.3 V output voltage and up to 5 A load
current with high efficiency and output accuracy in a very small solution size. The EVM provides multiple power
connectors and test points. It also provides a good layout example, which is optimized for EMI and thermal
performance.
Table 1-1. Device and Package Configurations
CONVERTER IC PACKAGE
U1 LMR51450 12-pin WSON package 3.0 mm × 3.0 mm × 0.75 mm
LMR51450EVM Front
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Table of Contents
1 Introduction.............................................................................................................................................................................3
1.1 LMR51450 Synchronous Step-Down Voltage Converter................................................................................................... 3
1.2 LMR51450 Evaluation Module........................................................................................................................................... 3
2 Quick Start...............................................................................................................................................................................4
3 Detailed Descriptions............................................................................................................................................................. 5
3.1 Connectors.........................................................................................................................................................................5
3.2 Jumpers..............................................................................................................................................................................6
4 Schematic................................................................................................................................................................................7
5 Board Layout...........................................................................................................................................................................8
6 Bill of Materials..................................................................................................................................................................... 10
7 Revision History....................................................................................................................................................................11
List of Figures
Figure 1-1. LMR51450 Pin Configuration (Top View).................................................................................................................. 3
Figure 1-2. LMR51450 Schematic............................................................................................................................................... 3
Figure 2-1. Top View of LMR51450 EVM.....................................................................................................................................4
Figure 4-1. LMR51450 EVM Schematic...................................................................................................................................... 7
Figure 5-1. Top 3D View.............................................................................................................................................................. 8
Figure 5-2. Top Layer...................................................................................................................................................................8
Figure 5-3. Signal Layer 1 - Ground Plane.................................................................................................................................. 8
Figure 5-4. Signal Layer 2 - Routing............................................................................................................................................8
Figure 5-5. Bottom Layer............................................................................................................................................................. 9
Figure 5-6. Bottom 3D view......................................................................................................................................................... 9
List of Tables
Table 1-1. Device and Package Configurations...........................................................................................................................1
Table 6-1. LMR51450 EVM Bill of Materials.............................................................................................................................. 10
Trademarks
All trademarks are the property of their respective owners.
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1 Introduction
1.1 LMR51450 Synchronous Step-Down Voltage Converter
The LMR51450 device is an easy-to-use synchronous step-down DC/DC converter capable of driving up to 5 A
of load current from a supply voltage ranging from 4 V to 36 V. The LMR51450 provides very high efficiency and
output accuracy in a very small solution size. The LMR51450 is capable of delivering 5 A of load current and
is peak current mode controlled. The following are additional features that provide both flexible and easy-to-use
solutions for a wide range of applications:
• Adjustable switching frequency
• FPWM variant (LMR51450FNDRRR)
• Power-good flag
• Precision enable
Automatic frequency foldback at light load improves efficiency over the entire load range. The device requires
few external components and PFM variant integrates Spread Spectrum for optimal EMI. Protection features
include the following:
• Thermal shutdown
• Input undervoltage lockout
• Cycle-by-cycle current limiting
• Hiccup short-circuit protection
The LMR51450 device is pin-to-pin compatible with the LMR51440 for easy output current scaling.
For a quick reference, Figure 1-1 shows the pin configuration of the LMR51450 and Figure 1-2 shows the
simplified schematic. See the LMR51450 4-V to 36-V, 5-A, Synchronous Step-Down DC/DC Converter Data
Sheet for more detailed feature descriptions and design guide.
Figure 1-1. LMR51450 Pin Configuration (Top View) Figure 1-2. LMR51450 Schematic
1.2 LMR51450 Evaluation Module
The LMR51450 EVM has the board populated with the LMR51450SDRRR and limiting current to 5 A and comes
with auto mode enabled.
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2 Quick Start
1. Connect the voltage supply between the VIN and GND connectors or between VIN_EMI and GND of J5 to
include the on-board input filter in the input path. Use short and thick gauge wires to minimize inductance
and IR drop. Note that sense points for VIN and VOUT are provided.
2. Connect the load of the converter between VOUT and GND connectors using short and thick wires.
3. Set the supply voltage at an appropriate level between 7 V to 36 V. The 7 V minimum ensures enough head
room for VOUT to equal 5 V at a 5-A load current. Set the current limit of the supply to an appropriate level to
supply needed current and protection.
4. Turn on the power supply. With the default configuration, the EVM powers up and provides VOUT = 5 V.
5. Monitor the output voltage with sense points. The maximum load current must be 5 A with the LMR51450.
Note that the maximum output current need to derate if ambient temperature is high, especially if device is
operated at higher frequency, for example, 1 MHz.
See Figure 2-1 for connector locations.
Figure 2-1. Top View of LMR51450 EVM
CAUTION
Caution Hot surface.
Contact may cause burns.
Do not touch.
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3 Detailed Descriptions
3.1 Connectors
This section describes the connectors on the EVM and how to properly connect, set up, and use the EVM. See
Figure 2-1 for a top view of the EVM.
VOUT Output voltage of the converter
The VOUT connector connects to the power inductor and output capacitors. Connect the load
between VOUT connector and the GND connector right next to it to provide load current. Connect
the loading device to the board with short and thick wires to handle the large DC output current.
GND1-
GND5
Ground of the converter
The GND is connected to the PGND and AGND pins of the device, as well as the ground of the
input and output capacitors. The GND connections next to VIN, VIN_EMI, and VOUT connectors
are meant for current return path for the supply voltage and load, respectively. Connectors are
provided in pairs to allow easy and accurate sensing of voltages. Connect to supply and load
grounds with short and thick wires. Other GND connectors are for signal measurement and
probing.
VIN Input voltage to the converter
The VIN connector connects to the input capacitors and the VIN pins of the LMR51450. Connect
the supply voltage from a power supply or a battery between VIN and GND connectors as power
input to the device. The voltage range must be higher than 3.9 V for the device to start up. VIN
higher than 6 V provides regulated 5-V output voltage. VIN must be no higher than 36 V to avoid
damaging the device. After start-up, the device stays active until VIN drops below 3.4 V. The
current limit on the supply must be high enough to provide the needed supply current. Otherwise,
the supply voltage does not maintain the desired voltage. The supply voltage must be connected
to the board with short and thick wires to handle the pulsing input current.
VIN_EMI Input voltage to input filter of the converter
LMR51450 EVM provides the option for the use of input filter. C1, C2 and L4 are placeholders
for input filter networks to be populated. If the input filter is desired between the supply and the
LMR51450, put C1, C2, and L4 on the board and connect the supply voltage between VIN_EMI
and GND_EMI connectors. The supply voltage must be connected to the board with short and
thick wires to handle pulsing input current. The output of the filter is connected to VIN, which is
connected to the VIN pins of the LMR51450 and the input capacitors.
GND_EMI Ground return for the input filter
This connector is the current return path for the supply connected to VIN_EMI. This connector
provides a short-loop connection to the input filter capacitors to best filter the conducted noise
generated from the PCB. Use VIN_EMI and GND_EMI connection if input filter is used and
conducted EMI test is desired.
EN To monitor the EN pin or input EN control signal
This test point is used to monitor the voltage on the device EN pin. By default, the EN pin is
connected to Vin.
PG To monitor the PGOOD pin
The PGOOD flag indicates whether the output voltage is within the regulation band. The PGOOD
pin of the device is an open-drain output and it is pulled up to VOUT on this board through a pullup
resistor. This flag is high impedance when the output voltage is in regulation.
VO This connector is provided to allow VOUT to be measured more accurately.
VI This connector is provided to allow VIN to be measured more accurately.
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3.2 Jumpers
This section describes the jumpers on the EVM. See Figure 2-1 for a top view of the EVM.
J2 This jumper allows the PG pin to be pulled up through 16k ohm resistor to Vout.
J3 This jumper allows the selection of an adjustable input UVLO.
J4 This jumper allows the selection of output voltage to be 5 V or 3.3 V.
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4 Schematic
The bill of materials of the EVM is tabulated in Bill or Materials . In addition, Figure 4-1 shows the corresponding
schematic.
Figure 4-1. LMR51450 EVM Schematic
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5 Board Layout
Figure 5-1 through Figure 5-6 show the board layout for the LMR51450 EVM. The EVM offers resistors,
capacitors, and test points to configure the following:
• Output voltage
• Precision enable
• Set frequency
The 12-pin WSON package offers a very small solution size. The PCB consists of a 4-layer design. There are
2-oz copper planes on the top and bottom and 1-oz copper mid-layer planes to dissipate heat with an array of
thermal vias to connect to all four layers.
Test points have been provided for ease of use to connect the power supply and required load, and to monitor
critical signals.
Figure 5-1. Top 3D View Figure 5-2. Top Layer
Figure 5-3. Signal Layer 1 - Ground Plane Figure 5-4. Signal Layer 2 - Routing
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Figure 5-5. Bottom Layer Figure 5-6. Bottom 3D view
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6 Bill of Materials
The bill of material is shown in Table 6-1 for the LMR51450 EVM.
Table 6-1. LMR51450 EVM Bill of Materials
DESIGNATOR QTY DESCRIPTION PART NUMBER MANUFACTURER
PCB 1 Printed Circuit Board BSR246 Rev A Any
C4, CO6 2 CAP, CERM, 1000 pF, 50 V,+/- 10%, X7R,
0603 885012206083 Wurth Elektronik
C5, CO5, CO7 3 CAP, CERM, 0.1 uF, 50 V, +/- 5%, X7R, 0805 08055C104JAT2A AVX
C6, C7 2 CAP, CERM, 4.7 uF, 50 V, +/- 10%, X7R, AEC-
Q200 Grade 1, 1210
CGA6P3X7R1H475K250
AB TDK
C8 1
CAP, Aluminum Polymer, 100 uF, 63 V, +/-
20%, 0.024 ohm, SMD, 2-Leads, Dia 10.5 mm,
Pin Spacing 8 mm SMD
PCR1J101MCL1GS Nichicon
CBoot 1 CAP, CERM, 0.1 uF, 50 V, +/- 10%, X7R, 0603 06035C104KAT2A AVX
CFF 1 CAP, CERM, 33 pF, 50 V, +/- 5%, C0G/NP0,
0603 06035A330JAT2A AVX
CO2, CO4 2 CAP, CERM, 47 uF, 10 V, +/- 20%, X7R, 1210 GRM32ER71A476ME15L MuRata
EN, VI, VO 3 Test Point, Multipurpose, Purple, TH 5129 Keystone Electronics
GND1, GND2, GND3,
GND4, GND5 5 Test Point, Multipurpose, Black, TH 5011 Keystone Electronics
J1, J4 2 Header, 100mil, 2x1, Gold, TH TSW-102-07-G-S Samtec
J2, J3 2 Header, 100mil, 3x1, Gold, TH TSW-103-07-G-S Samtec
J5, J6, J7 3 Terminal Block, 2x1, 5 mm, Green, TH 1935776 Phoenix Contact
L1 1 Inductor, Shielded Drum Core, Powdered Iron,
4.7 uH, 7 A, 0.015 ohm, SMD 74437368047 Wurth Elektronik
LBL1 1 Thermal Transfer Printable Labels, 0.650" W x
0.200" H - 10,000 per roll THT-14-423-10 Brady
R1, Rc, RFF 3 RES, 0, 5%, 0.1 W, 0603 RC0603JR-070RL Yageo, Yageo
America
R_PG, RENB, RFBB 3 RES, 16.0 k, 1%, 0.1 W, 0603 RC0603FR-0716KL Yageo
RENT 1 RES, 68.1 k, 1%, 0.1 W, 0603 RC0603FR-0768K1L Yageo
RFBT1 1 RES, 49.9 k, 1%, 0.1 W, 0603 RC0603FR-0749K9L Yageo
RFBT2 1 RES, 34.0 k, 1%, 0.1 W, 0603 RC0603FR-0734KL Yageo
Rinj 1 RES, 49.9, 1%, 0.1 W, 0603 RC0603FR-0749R9L Yageo
RT 1 RES, 31.6 k, 1%, 0.1 W, AEC-Q200 Grade 0,
0603 CRCW060331K6FKEA Vishay-Dale
SH-J2, SH-J3, SH-J4 3 Shunt, 100mil, Tin plated, Black SNT-100-BK-T-H Samtec
SW 1 Test Point, Miniature, SMT 5019 Keystone
U1 1 36-V, 5-A Synchronous Step-down Converter LMR51450SDRR Texas Instruments
C1, C2 0 CAP, CERM, 1 uF, 50 V, +/- 10%, X7R, AEC-
Q200 Grade 1, 1210
CGA6L2X7R1H105K160A
ATDK
CO1, CO3 0 CAP, CERM, 47 uF, 10 V, +/- 20%, X7R, 1210 GRM32ER71A476ME15L MuRata
D1 0 Diode, Schottky, 40 V, 1 A, SOD-123 1N5819HW-7-F Diodes Inc.
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