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LM25576 Reference Design
6-42V input, 5V 3A output
National Semiconductor
Reference Design 128
Richard Levin
January 2007
1.0 Design Specifications
Inputs Output #1
vInMin=6V vOut1=5V
vInMax=42V iOut1=3A
2.0 Design Description
This LM25576 reference design is based on a LM25576
demonstration board which was a assembled and tested plat-
form to evaluate the LM25576 SIMPLE SWITCHER® step-
down converter. The reference design takes a 6V-42V input
and generates a regulated 5V output that can source up to 3A
of current.
Design Targets
The primary consideration for this design was to obtain the
highest efficiency LM25576 design, over it’s full operating
voltage input range. Cost and size of components were a
secondary consideration (i.e.: using small, less expensive ce-
ramic capacitors; a small, off the shelf inductor; etc.). The
result is a design that achieves 95% peak efficiency, with a
short list of necessary components. All optional features of
the LM25576 can be enabled if necessary. The board layout
is ideal for demonstrating the capabilities of the target design,
while allowing for easy probing and adjustments.
Product Description
The LM25576 is an easy to use Simple Switcher buck regu-
lator which allows design engineers to design and optimize a
robust power supply using a minimum set of components.
Operating with an input voltage range of 6 - 42V, the LM25576
delivers 3A of continuous output current with an integrated
170 mΩ N-Channel MOSFET. The regulator utilizes an Em-
ulated Current Mode architecture which provides inherent line
regulation, tight load transient response, and ease of loop
compensation without the usual limitation on low-duty cycles
associated with current mode regulators. The operating fre-
quency is adjustable from 50 kHz to 1 MHz to allow optimiza-
tion of size and efficiency. To reduce EMI, a frequency
synchronization pin allows multiple IC’s from the LM2557x
family to self-synchronize or to synchronize to an external
clock. The LM25576 guarantees robustness with cycle-by-
cycle current limit, short-circuit protection, thermal shut-down,
and remote shut-down. The device is available in a power
enhanced TSSOP-20 package featuring an exposed die at-
tach pad for thermal dissipation.
The LM25576 is supported by the full suite of WEBENCH®
On-Line design tools
3.0 Features
■ SIMPLE SWITCHER® regulator
■ 6-42V input operation
■ Synchronizeable switching frequency
■ Regulated 5V output at up to 3A
■ 300 kHz switching frequency
■ Easily adjustable output voltage down to 1.225V
■ 95% maximum efficiency
■ On-board shutdown circuitry
■ Also demonstrates LM5576
■ Integrated WEBENCH design
■ RoHS compliant
■ Design was assembled and tested
Applications
■ Step-down 36V, 24V, or 12V rail to regulated 5V output
■ Robust, industrial power supply
■ Automotive applications
■ White goods power supplies
© 2007 National Semiconductor Corporation www.national.com
LM25576 Reference Design 6-42V input, 5V 3A output RD-128
Verzeichnis
- ・ Abmessungen des Paketumrisses on Seite 8
- ・ Blockdiagramm on Seite 2
- ・ Technische Daten on Seite 1
- ・ Anwendungsbereich on Seite 1 Seite 15
