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User's Guide

SNVA614B–January 2012–Revised January 2014

AN-2205 LM25118 Evaluation Board

1 Introduction

The LM25118 Evaluation Board is designed to provide the design engineer with a fully functional,

Emulated Current Mode Control, buck-boost power converter to evaluate the LM25118 controller IC. The

evaluation board provides a 12 V output with 3 A of output current capability. The evaluation board’s wide

input voltage range is from 42 V to 5 V, with operation down to 3 V with some component changes. The

evaluation board operates at 300 kHz, a good compromise between conversion efficiency, tradeoffs

between buck and buck-boost mode requirements, and converter size. The printed circuit board consists

of 4 layers with 2 ounce copper top and bottom, and 1 ounce copper on internal layers. The board is

constructed with FR4 material. This user' guide contains the evaluation board schematic, bill-of-materials

(BOM) and a quick setup procedure. For more complete circuit and design information, see the

LM25118/LM25118Q Wide Voltage Range Buck-Boost Controller (SNVS726) data sheet and quick start.

The performance of the evaluation board is as follows:

• Input Range: 42 V to less than 5 V at Full Current

• Operation to 3 V at Reduced Current and Appropriate Adjustments*

• Output Voltage: 12 V

• Output Current: 0 to 3 A

• Frequency of Operation: 300 kHz

• Board Size: 3.45 X 2.65 inches

• Load Regulation: 1%

• Line Regulation: 0.1%

• Over-Current Limiting

• Operation with V

Greater or Less than V

OUT

*Operation at full current to around 3 V is possible with current limit sense resistor, UVLO threshold, and

corresponding C

ramp

adjustment. Additional input capacitance may be required. For more details, see the

LM25118/LM25118Q Wide Voltage Range Buck-Boost Controller (SNVS726) data sheet.

2 IC Features

• Integrated High and Low Side Driver

• Internal High Voltage Bias Regulator

• Wide Input Voltage Range: 5 V to 42 V

• Emulated Current Mode Control

• Single Inductor Architecture

• V

OUT

Operation below and above V

• Single Resistor Sets Oscillator Frequency

• Oscillator Synchronization Capability

• Programmable Soft-Start

• Ultra Low (<10 µA) Shutdown Current

• Enable Input

• Wide Bandwidth Error Amplifier

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SNVA614B–January 2012–Revised January 2014 AN-2205 LM25118 Evaluation Board

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Summary of content (16 pages)

PAGE 1
User's Guide SNVA614B – January 2012 – Revised January 2014 AN-2205 LM25118 Evaluation Board 1 Introduction The LM25118 Evaluation Board is designed to provide the design engineer with a fully functional, Emulated Current Mode Control, buck-boost power converter to evaluate the LM25118 controller IC. The evaluation board provides a 12 V output with 3 A of output current capability. The evaluation board’s wide input voltage range is from 42 V to 5 V, with operation down to 3 V with some component changes.
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Package • • • • 3 www.ti.com Adjustable Output Voltage 1.23 V – 38 V 1.5% Feedback Reference Accuracy Thermal Shutdown No VIN to VOUT Connection during Fault Protection Package HTSSOP-20EP (Exposed Pad) 4 Application Circuit See the detailed LM25118EVAL schematic at Figure 17.
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Efficiency www.ti.com 5 Efficiency Figure 1. Efficiency Figure 1 illustrates the efficiency of the converter vs. input voltage and output current. These curves highlight the high efficiency of the converter, especially considering the simplicity of design offered by a non synchronous implementation. Note the discontinuity in the curves at approximately 17 V and 13 V which represent mode transition boundaries.
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Powering Up 7 www.ti.com Powering Up Connecting the IC’s enable pin to ground will allow powering up the source supply with a minimal output load. Set the current limit of the source supply to provide about 1.5 times the anticipated wattage of the load. Note that input currents become very high at low input voltages, which requires an appropriate input supply. As you remove the connection from the enable pin to ground, immediately check for 12 V at the output.
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Mode Transition www.ti.com Figure 4. Mode Transition Figure 4 illustrates soft mode transition. The boost switch pulse-width is relatively narrow compared to the buck switch waveform. The boost switch pulse-width will gradually increase as VIN decreases, and will eventually match and lock to the buck switch waveform. At this point, the converter enters full buck-boost operation.
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Typical Waveforms 11 www.ti.com Typical Waveforms Note: All waveforms refer to Rev B design. 6 Figure 5. VIN = 10 V, IOUT = 1 A, illustrating Buck-Boost Operation CH1: VSW = 20V/div; CH2: Q1 = 20V/div; CH3: Q2 = 10V/div; CH4: IL = 5A/div Figure 6. VIN = 18 V, IOUT = 3 A Illustrating Buck Operation CH1: VSW = 20V/div; CH2: Q1 = 20V/div; CH3: Q2 = 10V/div; CH4: IL = 2A/div Figure 7. Buck Mode Transient Response CH2: VOUTripple (ac coupled); CH4: IOUT Figure 8.
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Typical Waveforms www.ti.com Figure 9.
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Bill of Materials 12 Bill of Materials Quant Designator ity 8 www.ti.com Description Manufacturer PartNumber 5 C1, C2, C3, C4, C5 CAP, CERM, 2.2uF, 100V, +/-20%, X7R, 1812 TDK C4532X7R2A225M 3 C6, C16, C17 CAP, CERM, 0.1uF, 100V, +/-10%, X7R, 0603 MuRata GRM188R72A104KA35D 2 C7, C8 CAP, AL, 180uF, 16V, +/-20%, 0.026 ohm, SMD Nippon Chemi-Con APXH160ARA181MJ80G 2 C9, C10 CAP, CERM, 47uF, 16V, +/-10%, X5R, 1210 MuRata GRM32ER61C476KE15L 2 C11, C12 CAP, CERM, 0.
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Printed Circuit Board Layout www.ti.com 13 Printed Circuit Board Layout Figure 10. Top Layer as Viewed from Top Figure 11. Copper Layer 1 (Top) as Viewed from Top Figure 12. Copper Layer 2 (Mid-Layer 1) as Viewed from Top Figure 13.
PAGE 10
Printed Circuit Board Layout www.ti.com Figure 14. Copper Layer4 (Bottom) as Viewed from Top Figure 15. Bottom Layer as Viewed from Top Figure 16.
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Evaluation Board www.ti.com 14 Evaluation Board Figure 17.
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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.
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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.
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【Important Notice for Users of EVMs for RF Products 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.
PAGE 15
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.