LM2574
Micrel
LM2574
52kHz Simple 0.5A Buck Regulator
General Description
Features
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)switchingregulatorandrequiresaminimum
of external components.
• 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
TheLM2574isavailablein3.3Vand5Vfixedoutputversions,
oranadjustableversionwithanoutputvoltagerangeof1.23V
to 37V. Output voltage is guaranteed to ±4% for specified
input and load conditions.
TheLM2574cansupply0.5Awhilemaintainingexcellentline
and load regulation. The output switch includes cycle-by-
cycle current limiting, as well as thermal shutdown for full
protection under fault conditions.
• 52kHz fixed frequency internal oscillator
• Uses standard inductors
Applications
Anexternalshutdownconnectionselectsoperatingorstandby
modes. Standby current is less than 200µA.
• Simple high-efficiency step-down (buck) regulator
• Efficient pre-regulator for linear regulators
• On-card switching regulators
Heat sinks are generally unnecessary due the regulator’s
highefficiency. Adequateheattransferisusuallyprovidedby
soldering all package pins to a printed circuit board.
• Positive to negative converter (buck-boost)
The LM2574 includes internal frequency compensation and
an internal 52kHz fixed frequency oscillator guaranteed to
±10% of the frequency.
Ordering Information
Part Number
LM2574BN
Junction Temp. Range
–40°C to +85°C
Package
8-pin Plastic DIP
8-pin Plastic DIP
8-pin Plastic DIP
Circuits constructed around the LM2574 use a standard
series of inductors which are available from several different
manufacturers.
LM2574-3.3BN
LM2574-5.0BN
–40°C to +85°C
–40°C to +85°C
All support documentation can be found on Micrel’s web
site at www.micrel.com.
Typical Application
40V MAX
UNREGULATED
DC IN
FB
VIN
REGULATED
OUTPUT
0.5A
CIN
22µF
330µH
LM2574
OUT
PWR
SIG ON/
GND GND OFF
COUT
220µF
11DQ05
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
M9999-122303
December 2003
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