LM27402 Datasheet, PDF (1/32 Pages) National Semiconductor (TI) – High Performance Synchronous Buck Controller with DCR Current Sensing

LM27402
September 2, 2010
High Performance Synchronous Buck Controller with DCR
Current Sensing
General Description
The LM27402 is a synchronous voltage mode DC/DC buck
controller with inductor DCR current sense capability. Sens-
ing the inductor current eliminates the need to add resistive
powertrain elements which increases overall efficiency and
facilitates accurate continuous current limit sensing. A 0.6V
±1% voltage reference enables high accuracy and low volt-
age capability at the output. An input operating voltage range
of 3V to 20V makes the LM27402 suitable for a large variety
of input rails.
The LM27402 voltage mode control loop incorporates input
voltage feed-forward to maintain stability throughout the en-
tire input voltage range. The switching frequency is adjustable
from 200 kHz to 1.2 MHz. Dual high current integrated N-
channel MOSFET drivers support large Q_G, low R_DS(ON)
MOSFETs. A power good indicator provides power rail se-
quencing capability and output fault detection. Adjustable
external soft-start capability limits inrush current and provides
monotonic output control during startup. Other features in-
clude external tracking of other power supplies, integrated
LDO bias supply, and synchronization capability. The
LM27402 is offered in a 16 pin eTSSOP package and a 4 mm
x 4 mm 16 pin exposed LLP.
Features
■ ^{Input operating voltage range of 3V to 20V}
■ ^{Continuous inductor DCR or shunt resistor current sensing}
■ ^{0.6V ±1% reference (-40°C to 125°C junction}
temperature)
■ ^{Output voltage as high as 95% of input voltage}
■ ^{Integrated MOSFET drivers}
■ ^{Internal LDO bias supply}
■ ^{External clock synchronization}
■ ^{Adjustable soft-start with external capacitor}
■ ^{Pre-biased startup capability}
■ ^{Power supply tracking}
■ ^{Input voltage feed-forward}
■ ^{Power good indicator}
■ ^{Precision enable with hysteresis}
Applications
■ ^{High current, low voltage FPGA/ASIC DC/DC converters}
■ ^{General purpose high current buck converters}
■ ^{Telecom, datacom, networking, distributed power}
architectures
Typical Application Circuit
PowerWise^® is a registered trademark of National Semiconductor Corporation.
© 2010 National Semiconductor Corporation 300926
30092601
www.national.com