
LM22671/LM22671Q
January 20, 2011
500 mA SIMPLE SWITCHER, Step-Down Voltage
Regulator with Features
General Description
The LM22671 series of regulators are monolithic integrated
circuits which provide all of the active functions for a step-
down (buck) switching regulator capable of driving up to 500
mA loads with excellent line and load regulation characteris-
tics. High efficiency (>90%) is obtained through the use of a
low ON-resistance N-channel MOSFET. The series consists
of a fixed 5V output and an adjustable version.
The SIMPLE SWITCHER concept provides for an easy to
use complete design using a minimum number of external
components and National’s WEBENCH design tool.
National’s WEBENCH tool includes features such as exter-
nal component calculation, electrical simulation, thermal sim-
ulation, and Build-It boards for easy design-in. The switching
clock frequency is provided by an internal fixed frequency os-
cillator which operates at 500 kHz. The switching frequency
can also be adjusted with an external resistor or synchronized
to an external clock up to 1 MHz. It is also possible to self-
synchronize multiple regulators to share the same switching
frequency. The LM22671 series also has built in thermal shut-
down, current limiting and an enable control input that can
power down the regulator to a low 25 A quiescent current
standby condition. An adjustable soft-start feature is provided
by selecting an appropriate external soft-start capacitor.
Features
■ Wide input voltage range: 4.5V to 42V
■ Internally compensated voltage mode control
■ Stable with low ESR ceramic capacitors
■ 200 m N-channel MOSFET
■ Output voltage options:
-ADJ (outputs as low as 1.285V)
-5.0 (output fixed to 5V)
■ ±1.5% feedback reference accuracy
■ Switching frequency of 500 kHz, adjustable between 200
kHz and 1 MHz
■ -40°C to 125°C operating junction temperature range
■ Precision enable pin
■ Integrated boot diode
■ Adjustable soft-start
■ Fully WEBENCH enabled
■ Step-down and inverting buck-boost applications
■ LM22671Q is an Automotive Grade product that is AEC-
Q100 grade 1 qualified (-40°C to +125°C operating
junction temperature)
Package
■ PSOP-8 (Exposed Pad)
Applications
■ Industrial Control
■ Telecom and Datacom Systems
■ Embedded Systems
■ Automotive Telematics and Body Electronics
■ Conversions from Standard 24V, 12V and 5V Input Rails
Simplified Application Schematic
30076801
2011 National Semiconductor Corporation
300768
www.national.com
LM22671/LM22671Q
500
mA
SIMPLE
SWITCHER,
Step-Down
Voltage
Regulator
with
Features