Datasheet

LM2655
2.5A High Efficiency Synchronous Switching Regulator
General Description
The LM2655 is a current-mode controlled PWM step-down
switching regulator. It has the unique ability to operate in
synchronous or asynchronous mode. This gives the de-
signer flexibility to choose between the high efficiency of
synchronous operation, or the low solution cost of asynchro-
nous operation. Along with flexibility, the LM2655 offers high
power density with the small footprint of a TSSOP-16 pack-
age.
High efficiency (
>
90%) is obtained through the use of an
internal low ON-resistance (33mΩ) MOSFET, and an exter-
nal N-Channel MOSFET. This feature, together with its low
quiescent current, makes the LM2655 an ideal fit in portable
applications.
Integrated in the LM2655 are all the power, control, and drive
functions for asynchronous operation. In addition, a low-side
driver output allows easy synchronous operation. The IC
uses patented current sensing circuitry that eliminates the
external current sensing resistor required by other current-
mode DC-DC converters. A programmable soft-start feature
limits start up current surges and provides a means of se-
quencing multiple power supplies.
Features
n Ultra-high efficiency up to 96%
n 4V to 14V input voltage range
n Internal high-side MOSFET with low R
DS(ON)
= 0.033Ω
n 300 kHz fixed frequency internal oscillator
n Low-side drive for synchronous operation
n Guaranteed less than 12 µA shutdown current
n Patented current sensing for current mode control
n Programmable soft-start
n Input undervoltage lockout
n Output overvoltage shutdown protection
n Output undervoltage shutdown protection
n Thermal Shutdown
n 16-pin TSSOP package
Applications
n Hard disk drives
n Internet appliances
n TFT monitors
n Computer peripherals
n Battery powered devices
Typical Application
10128429
April 2005
LM2655 2.5A High Efficiency Synchronous Switching Regulator
© 2005 National Semiconductor Corporation DS101284 www.national.com