
LM3151/LM3152/LM3153
August 26, 2009
SIMPLE SWITCHER CONTROLLER, High Input Voltage
Synchronous Step-Down
General Description
The LM3151/2/3 SIMPLE SWITCHER Controller is an easy
to use and simplified step down power controller capable of
providing up to 12A of output current in a typical application.
Operating with an input voltage range from 6V-42V, the
LM3151/2/3 features a fixed output voltage of 3.3V, and fea-
tures switching frequencies of 250 kHz, 500 kHz, and 750
kHz. The synchronous architecture provides for highly effi-
cient designs. The LM3151/2/3 controller employs a Constant
On-Time (COT) architecture with a proprietary Emulated Rip-
ple Mode (ERM) control that allows for the use of low ESR
output capacitors, which reduces overall solution size and
output voltage ripple. The Constant On-Time (COT) regula-
tion architecture allows for fast transient response and re-
quires no loop compensation, which reduces external com-
ponent count and reduces design complexity.
Fault protection features such as thermal shutdown, under-
voltage lockout, over-voltage protection, short-circuit protec-
tion, current limit, and output voltage pre-bias startup allow for
a reliable and robust solution.
The LM3151/2/3 SIMPLE SWITCHER concept provides for
an easy to use complete design using a minimum number of
external components and National’s WEBENCH online de-
sign tool. WEBENCH provides design support for every step
of the design process and includes features such as external
component calculation with a new MOSFET selector, electri-
cal simulation, thermal simulation, and Build-It boards for
prototyping.
Features
■ PowerWise step-down controller
■ 6V to 42V Wide input voltage range
■ Fixed output voltage of 3.3V
■ Fixed switching frequencies of 250 kHz/500 kHz/750 kHz
■ No loop compensation required
■ Fully WEBENCH enabled
■ Low external component count
■ Constant On-Time control
■ Ultra-Fast transient response
■ Stable with low ESR capacitors
■ Output voltage pre-bias startup
■ Valley current limit
■ Programmable soft-start
Typical Applications
■ Telecom
■ Networking Equipment
■ Routers
■ Security Surveillance
■ Power Modules
Typical Application
30053201
SIMPLE SWITCHER is a registered trademark of National Semiconductor Corporation
2009 National Semiconductor Corporation
300532
www.national.com
LM3151/LM3152/LM3153
SIMPLE
SWITCHER
CONTROLLER,
High
Input
Voltage
Synchronous
Step-Down