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User's Guide

SNVA612B–January 2012–Revised April 2013

AN-2200 LM5017 Evaluation Board

1 Introduction

The LM5017 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 100 V.

The board’s specifications are:

• Input Range: 12.5 V to 95 V, transients up to 100 V (absolute maximum)

• Output Voltage: 10 V

• Output Current: 600 mA

• Nominal Switching Frequency ~ 200 kHz

• Measured Efficiency: 92.4% at 400 mA and V

= 24 V

• Board size: 2.95 in. x 1.8 in.

Figure 1. Evaluation Board (Top View)

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SNVA612B–January 2012–Revised April 2013 AN-2200 LM5017 Evaluation Board

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Summary of content (8 pages)

PAGE 1
User's Guide SNVA612B – January 2012 – Revised April 2013 AN-2200 LM5017 Evaluation Board 1 Introduction The LM5017 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 100 V. The board’s specifications are: • Input Range: 12.
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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 R3 VIN (1) The on-time of this evaluation board ranges from 5.56 µs at VIN = 12 V to 702 ns at VIN = 95 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.
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Board Connection and Start-up www.ti.com Table 1. Bill of Materials (BOM) Item Description U1 Sync Switching Regulator Package Value Texas Instruments, LM5017 SO PowerPAD-8 100 V, 0.6A Wurth, 7447714221 10 mm x 10 mm 220 µH, 1.2A Alternate Inductor Bourns, SRR1260–221k 12.5 mm x 12.5 mm 220 µH, 1.38A Alternate Inductor Coilcraft, MSS1246–224K 12.3 mm x 12.3 mm 220 µH, 1.
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Ripple Configuration 5 www.ti.com Ripple Configuration The LM5017 is a COT buck and requires adequate ripple at feedback (FB) node. Three commonly used ripple generation methods are shown in Table 2. LM5017 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 2. Table 2.
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Performance Curves www.ti.com 6 Performance Curves Figure 3. Efficiency vs Load Current Figure 4. Frequency vs Input Voltage Figure 5.
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PC Board Layout 7 www.ti.com PC Board Layout Figure 6. Board Silkscreen Figure 7.
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PC Board Layout www.ti.com Figure 8.
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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.