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User's Guide
SNVA326B–May 2008–Revised May 2013
AN-1792 LM20343 Evaluation Board
1 Introduction
This evaluation board provides a solution to examine the full featured LM20343 buck switching regulator
that is capable of driving up to 3A of load current. This device features a frequency adjust pin that allows
the switching frequency to be adjusted from 250 kHz to 1.0 MHz. The LM20343 is capable of down
converting from an input voltage between 4.5V and 36V. Fault protection features include cycle-by-cycle
current limit, output power good, and output over-voltage protection. The dual function soft-start/tracking
pin can be used to control the startup response of the LM20343, and the precision enable pin can be used
to easily sequence the LM20343 in applications with sequencing requirements.
The LM20343 evaluation board has been optimized to work from 4.5V to 25V achieving a balance
between overall solution size with the efficiency of the regulator. The evaluation board measures just
under 2” x 2” on a four layer PCB, and exhibits a thermal characteristic of 27°C/W with no air flow. The
power stage and compensation components of the LM20343 evaluation board have been optimized for an
input voltage of 12V, but for testing purposes, the input can be varied across the entire operating range.
The output voltage of the evaluation board is nominally 3.3V, but this voltage can be easily changed by
replacing one of the feedback resistors (R5 or R6).
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SNVA326B–May 2008–Revised May 2013 AN-1792 LM20343 Evaluation Board
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