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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 lower-
frequency switching regulators. The internal switch is an 0.25 Ω DMOS device, providing very high-
efficiency 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 C
IN
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.
1
SNVA011C–February 1999–Revised April 2013 AN–1120 LM2675-5.0EVAL 1A Step-Down High-Efficiency SIMPLE
SWITCHER Evaluation Board
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