LM2574
Micrel
LM2574
52kHz Simple 0.5A Buck Regulator
General Description
The LM2574 family is a series of easy to use fixed and
adjustable switching voltage regulators. The LM2574 con-
tains all of the active circuitry necessary to construct a
stepdown (buck) switching regulator and requires a minimum
of external components.
The LM2574 is available in 3.3V and 5V fixed output versions,
or an adjustable version with an output voltage range of 1.23V
to 37V. Output voltage is guaranteed to
±4%
for specified
input and load conditions.
The LM2574 can supply 0.5A while maintaining excellent line
and load regulation. The output switch includes cycle-by-
cycle current limiting, as well as thermal shutdown for full
protection under fault conditions.
An external shutdown connection selects operating or standby
modes. Standby current is less than 200µA.
Heat sinks are generally unnecessary due the regulator’s
high efficiency. Adequate heat transfer is usually provided by
soldering all package pins to a printed circuit board.
The LM2574 includes internal frequency compensation and
an internal 52kHz fixed frequency oscillator guaranteed to
±10%
of the frequency.
Circuits constructed around the LM2574 use a standard
series of inductors which are available from several different
manufacturers.
All support documentation can be found on Micrel’s web
site at www.micrel.com.
Features
• 3.3V, 5V, 12V, and adjustable output versions
• Adjustable version output 1.23V to 37V
±4%
max. over
line and load conditions.
• Guaranteed 0.5A output current
• Wide input voltage, up to 40V
• Thermal shutdown and current limit protection
• Requires only 4 external components.
• Shutdown capability (standby mode)
• Low power standby mode < 200µA Typical
• High-efficiency
• 52kHz fixed frequency internal oscillator
• Uses standard inductors
Applications
•
•
•
•
Simple high-efficiency step-down (buck) regulator
Efficient pre-regulator for linear regulators
On-card switching regulators
Positive to negative converter (buck-boost)
Ordering Information
Part Number
LM2574BN
LM2574-3.3BN
LM2574-5.0BN
Junction Temp. Range
–40°C to +85°C
–40°C to +85°C
–40°C to +85°C
Package
8-pin Plastic DIP
8-pin Plastic DIP
8-pin Plastic DIP
Typical Application
40V MAX
UNREGULATED
DC IN
V
IN
C
IN
22µF
PWR
GND
LM2574
SIG
GND
OUT
ON/
OFF
11DQ05
330µH
FB
REGULATED
OUTPUT
0.5A
C
OUT
220µF
Figure 1. Fixed Output Regulator Circuit
Micrel, Inc. • 1849 Fortune Drive • San Jose, CA 95131 • USA • tel + 1 (408) 944-0800 • fax + 1 (408) 944-0970 • http://www.micrel.com
December 2003
1
M9999-122303
MICREL [ MICREL SEMICONDUCTOR ]
