Texas Instruments LMR51450 EVM Manual de usuario

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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LMR51450 EVM 1

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.

Bill of Materials www.ti.com

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