LM2675-5.0EVAL

User's Guide SNVA011C – February 1999 – Revised April 2013 AN–1120 LM2675-5.0EVAL 1A Step-Down High-Efficiency SIMPLE SWITCHER Evaluation Board The LM2675-5.0EVAL evaluation board is a fully-assembled and tested surface-mount regulator that provides a 5 V±1.5% output at up to 1A, from an input of 8 V to 40 V. The overall efficiency is typically as high as 90%. The operating temperature range is 0°C to +85°C. 1 Introduction The LM2675 SIMPLE SWITCHER® step-down regulator provides all the active functions for a step-down regulator capable of driving a 1A load with excellent line and load regulation. Switching frequency is internally set to 260 kHz, allowing smaller-sized filter components than would be needed with lowerfrequency switching regulators. The internal switch is an 0.25 Ω DMOS device, providing very highefficiency power conversion. With this high efficiency, the copper traces on the printed circuit board are the only heat sinking needed. 2 Evaluation Board Design This evaluation board is designed for supplying 5 V at up to 1 Amp to a load. The input voltage range is 8 V to 40 V. Components, shown in the schematic of Figure 1, were selected based on the design procedure in the LM2675 data sheet. The layout is very important in switching regulator designs. Rapidly switching currents associated with wiring inductance can generate voltage transients that can cause problems. For minimal inductance and ground loops, the traces that carry the highest currents (input, ground, switch, and output signals) are relatively wide and short. The external components are located physically close to the IC. Components in this design were selected according to the design procedure in the LM2675 SIMPLE SWITCHER® Power Converter High Efficiency 1A Step-Down Voltage Regulator Data Sheet (SNVS129). The input capacitor CIN was chosen for its voltage rating and RMS current rating. A 40 V maximum input requires a capacitor with voltage rating of at least 1.25x40, or 50 V. A conservative estimate of RMS input current is approximately ½ the DC load current. The input capacitor chosen for this application has a voltage rating of 50 V and an RMS current rating of 900 mA. The inductor and output capacitor were selected for a combination of good regulator stability and compact size, according to the design tables in the data sheet. While the LM2675 has an ON/OFF control, this has not been provided on the evaluation board. The parts list for this board is given in Table 1, while contact information for the component manufacturers is given in Table 2. SIMPLE SWITCHER is a registered trademark of Texas Instruments. All other trademarks are the property of their respective owners. SNVA011C – February 1999 – Revised April 2013 Submit Documentation Feedback AN–1120 LM2675-5.0EVAL 1A Step-Down High-Efficiency SIMPLE SWITCHER Evaluation Board Copyright © 1999–2013, Texas Instruments Incorporated 1 Operating the Evaluation Board www.ti.com Figure 1. LM2675-5.0EVAL Schematic Table 1. Parts List (Bill of Materials) Designator Description Quantity U1 LM2675M-5.0 Texas Instruments SIMPLE SWITCHER voltage converter 1 CIN 15 µF, 50 V Solid Tantalum, Sprague type 594D 1 COUT 68 µF, 16 V Solid Tantalum, Sprague type 595D 1 D1 1A, 40 V Schottky rectifier 1 L1 47 µH Power Inductor, Coilcraft D03316-473 1 CB 0.01 µF, 50 V Ceramic 1 Table 2. Component Manufacturers 3 Manufacturer Phone FAX Internet Texas Instruments (800) 272-9959 (800) 737-7018 www.ti.com Coilcraft Inc. (800) 322-2645 (708) 639-1469 www.coilcraft.com Coilcraft Inc., Europe +44 1236 730 595 +44 1236 730 627 www.coilcraft.com Sprague/Vishay (207) 324-7223 (207) 324-4140 www.vishay.com Operating the Evaluation Board The input source for the LM2675-5.0 evaluation board must be greater than 8 V for proper startup and operation. The maximum input voltage is 40 V, including transients. During startup, the LM2675 may be left unloaded. If a load is connected, the peak current drawn from the source may be as great as 2.2A (for a full 1A load). A source with a lower current limit will slow down the startup of the regulator. If its current limit is sufficiently low, typically at or near the steady-state input current level, the regulator may not start up at all. The load for the evaluation board can be from 0 Amps (an open-circuit) to 1 Amp. Higher load currents can activate the LM2675 current limit, which will shut the regulator down until the load is reduced. 4 Designing with the LM2675 The LM2675 SIMPLE SWITCHER step-down converters are available in fixed output voltages of 3.3 V, 5.0 V, 12 V, and an adjustable output version, each rated for a 1A load. A family of standard inductors for use with the LM2675 are available from several manufacturers, which greatly simplifies the design of switch-mode power supplies. The data sheet also includes selection guides for diodes and capacitors designed to work in these switching regulator designs. 2 AN–1120 LM2675-5.0EVAL 1A Step-Down High-Efficiency SIMPLE SWITCHER Evaluation Board SNVA011C – February 1999 – Revised April 2013 Submit Documentation Feedback Copyright © 1999–2013, Texas Instruments Incorporated References www.ti.com While the LM2675 SIMPLE SWITCHER® Power Converter High Efficiency 1A Step-Down Voltage Regulator Data Sheet (SNVS129) contains an easy, straight-forward design procedure, design software is also available, which further simplifies the system design. “LM267X Made Simple” is available from the Texas Instruments web site at www.ti.com. 5 References LM2675 SIMPLE SWITCHER® Power Converter High Efficiency 1A Step-Down Voltage Regulator Data Sheet (SNVS129) SNVA011C – February 1999 – Revised April 2013 Submit Documentation Feedback AN–1120 LM2675-5.0EVAL 1A Step-Down High-Efficiency SIMPLE SWITCHER Evaluation Board Copyright © 1999–2013, Texas Instruments Incorporated 3 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. 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