LM2575
52kHz Simple 1A Buck Regulator
General Description
The LM2575 series of monolithic integrated circuits
provide all the active functions for a step-down (buck)
switching regulator. Fixed versions are available with a
3.3V, 5V, 12V, fixed output. Adjustable versions have an
output voltage range from 1.23V to 37V. Both versions are
capable of driving a 1A load with excellent line and load
regulation.
These regulators are simple to use because they require a
minimum number of external components and include
internal frequency compensation and a fixed-frequency
oscillator.
The LM2575 series offers a high efficiency replacement for
popular three-terminal adjustable linear regulators. It
substantially reduces the size of the heat sink, and in
many cases no heat sink is required.
A standard series of inductors available from several
different manufacturers are ideal for use with the LM2575
series. This feature greatly simplifies the design of switch-
mode power supplies.
The feedback voltage is guaranteed to ±2% tolerance for
adjustable versions, and the output voltage is guaranteed
to ±3% for fixed versions, within specified input voltages
and output load conditions. The oscillator frequency is
guaranteed to ±10%. External shutdown is included,
featuring less than 200µA standby current. The output
switch includes cycle-by-cycle current limiting and thermal
shutdown for full protection under fault conditions.
Data sheets and support documentation can be found on
Micrel’s web site at www.micrel.com.
Features
•
3.3V, 5V, 12V, and adjustable output versions
•
Voltage over specified line and load conditions:
– Fixed version: ±3% max. output voltage
– Adjustable version: ±2% max. feedback voltage
•
Guaranteed 1A output current
•
Wide input voltage range
– 4V to 40V
•
Wide output voltage range
– 1.23V to 37V
•
Requires only 4 external components
•
52kHz fixed frequency internal oscillator
•
Low power standby mode IQ typically <200µA
•
80% efficiency (adjustable version typically >80%)
•
Uses readily available standard inductors
•
Thermal shutdown and current limit protection
•
100% electrical thermal limit burn-in
Applications
•
•
•
•
•
Simple high-efficiency step-down (buck) regulator
Efficient pre-regulator for linear regulators
On-card switching regulators
Positive to negative converter (inverting Buck-Boost)
Isolated flyback converter using minimum number of
external components
•
Negative boost converter
___________________________________________________________________________________________________________
Typical Applications
7V–40V
Unregulated
DC Input
1
4
Feedback
+5V, 1A
Regulated
Output
+
C
OUT
330µF
7V–40V
Unregulated
DC Input
1
4
LM2575
Feedback
+5V, 1A
Regulated
Output
+
C
OUT
330µF
R2 3.09k
R1 1k
+V
IN
+
C
IN
100µF
LM2575-5.0
Output L1
2
330µH
3
5
Gnd On/Off
D1
1N5822
+V
IN
+
C
IN
100µF
Output L1
2
330µH
D1
1N5822
3
5
Gnd On/Off
Note: Pin numbers are for TO-220 Package
Note: Pin numbers are for TO-220 Package
V
OUT
= 1.23 1 + R2
R1
(
)
Fixed Regulation in Typical Application
Adjustable Regulation in Fixed Output Application
Micrel Inc. • 2180 Fortune Drive • San Jose, CA 95131 • USA • tel +1 (
408
) 944-0800 • fax + 1 (408) 474-1000 • http://www.micrel.com
May 2009
1
M9999-051209-B
MICREL [ MICREL SEMICONDUCTOR ]
