
LM22670/LM22670Q
January 24, 2011
3A SIMPLE SWITCHER, Step-Down Voltage Regulator with
Synchronization or Adjustable Switching Frequency
General Description
The LM22670 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 3A
loads with excellent line and load regulation characteristics.
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 1MHz. It is also possible to self-
synchronize multiple regulators to share the same switching
frequency. The LM22670 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.
Features
■ Wide input voltage range: 4.5V to 42V
■ Internally compensated voltage mode control
■ Stable with low ESR ceramic capacitors
■ 120 m N-channel MOSFET TO-263 THIN package
■ 100 m N-channel MOSFET PSOP-8 package
■ 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
■ Integrated soft-start
■ Fully WEBENCH enabled
■ Step-down and inverting buck-boost applications
■ LM22670Q 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)
■ TO-263 THIN (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
30076001
2011 National Semiconductor Corporation
300760
www.national.com
LM22670/LM22670Q
3A
SIMPLE
SWITCHER,
Step-Down
Voltage
Regulator
with
Synchronization
or
Adjustable
Switching
Frequency