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Using the LM25019 Evaluation Board

User's Guide

SNVU225–April 2013

LM25019 Evaluation Board

1 Introduction

The LM25019 evaluation board provides the design engineer with a fully functional buck regulator,

employing the constant on-time (COT) operating principle. This evaluation board provides a 10 V output

over an input range of 12.5 V to 48 V.

The board’s specifications are:

• Input Range: 12.5 V to 48 V

• Output Voltage: 10 V

• Output Current: 100 mA

• Nominal Switching Frequency ~ 420 kHz

• Measured Efficiency: 90.2% at 100 mA and V

= 15 V

• Board size: 2.3 inch x 1.4 inch

Figure 1. Complete Evaluation Board Schematic for LM25019 Based Synchronous Buck Converter

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SNVU225–April 2013 LM25019 Evaluation Board

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Summary of content (11 pages)

PAGE 1
User's Guide SNVU225 – April 2013 LM25019 Evaluation Board 1 Introduction The LM25019 evaluation board provides the design engineer with a fully functional buck regulator, employing the constant on-time (COT) operating principle. This evaluation board provides a 10 V output over an input range of 12.5 V to 48 V. The board’s specifications are: • Input Range: 12.5 V to 48 V • Output Voltage: 10 V • Output Current: 100 mA • Nominal Switching Frequency ~ 420 kHz • Measured Efficiency: 90.
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Theory of Operation 2 www.ti.com Theory of Operation When the circuit is in regulation, the buck switch is turned on each cycle for a time determined by R3 and VIN according to Equation 1: TON = 10 -10 x R2 VIN (1) The on-time of this evaluation board ranges from 2.39 µs at VIN = 12 V to 493 ns at VIN = 48 V. The ontime varies inversely with input voltage. At the end of each on-time, the buck switch is off for at least 144 ns. In normal operation, the off-time is much longer.
PAGE 3
Bill of Materials (BOM) www.ti.com 5 Bill of Materials (BOM) Designat or Value Description C1 0.01uF CAP, CERM, 0.01uF, 16V, +/-10%, X7R, 0603 C2 1uF CAP, CERM, 1uF, 50V, +10/%, X7R, 1206 C3 0.1uF C4 Package Reference PartNumber Manufacturer GRM188R71C103KA01D MuRata 1206 GRM31MR71H105KA88L MuRata CAP, CERM, 0.
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Ripple Configuration 6 www.ti.com Ripple Configuration The LM25019 is a COT buck and requires adequate ripple at feedback (FB) node. Three commonly used ripple generation methods are shown in Table 1. LM25019 evaluation board has been supplied with minimum ripple configuration (Type 3), but can be configured to Type 1 or Type 2 with modifications as suggested in Table 1. Table 1.
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Performance Curves www.ti.com 7 Performance Curves 100 VIN=15V VIN=24V VIN=36V 90 80 Efficiency (%) 70 60 50 40 30 20 10 0 0 20 40 60 80 100 IOUT (mA) 120 C001 Figure 2. Efficiency vs Load Current 550 500 FREQUENCY (kHz) 450 400 350 300 250 200 150 100 50 10 15 20 25 30 35 40 INPUT VOLTAGE (V) 45 50 C002 Figure 3. Frequency vs Input Voltage (IOUT = 100 mA) Figure 4.
PAGE 6
PC Board Layout 8 www.ti.com PC Board Layout Figure 5. Top Silk Figure 6. Top Copper Figure 7.
PAGE 7
EVALUATION BOARD/KIT/MODULE (EVM) ADDITIONAL TERMS Texas Instruments (TI) provides the enclosed Evaluation Board/Kit/Module (EVM) under the following conditions: The user assumes all responsibility and liability for proper and safe handling of the goods. Further, the user indemnifies TI from all claims arising from the handling or use of the goods.
PAGE 8
FCC Interference Statement for Class B EVM devices This equipment has been tested and found to comply with the limits for a Class B digital device, pursuant to part 15 of the FCC Rules. These limits are designed to provide reasonable protection against harmful interference in a residential installation. This equipment generates, uses and can radiate radio frequency energy and, if not installed and used in accordance with the instructions, may cause harmful interference to radio communications.
PAGE 9
【Important Notice for Users of this Product in Japan】】 This development kit is NOT certified as Confirming to Technical Regulations of Radio Law of Japan If you use this product in Japan, you are required by Radio Law of Japan to follow the instructions below with respect to this product: 1. 2. 3. Use this product in a shielded room or any other test facility as defined in the notification #173 issued by Ministry of Internal Affairs and Communications on March 28, 2006, based on Sub-section 1.
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EVALUATION BOARD/KIT/MODULE (EVM) WARNINGS, RESTRICTIONS AND DISCLAIMERS For Feasibility Evaluation Only, in Laboratory/Development Environments. Unless otherwise indicated, this EVM is not a finished electrical equipment and not intended for consumer use.
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IMPORTANT NOTICE Texas Instruments Incorporated and its subsidiaries (TI) reserve the right to make corrections, enhancements, improvements and other changes to its semiconductor products and services per JESD46, latest issue, and to discontinue any product or service per JESD48, latest issue. Buyers should obtain the latest relevant information before placing orders and should verify that such information is current and complete.