LM2576 Micrel, Inc.
LM2576
52kHz Simple 3A Buck Regulator
General Description Features
The LM2576 series of monolithic integrated circuits provide 3.3V, 5V, 12V, and adjustable output versions
all the active functions for a step-down (buck) switching
Voltage over specified line and load conditions:
regulator. Fixed versions are available with a 3.3V, 5V, or 12V
Fixed version: 3% max. output voltage
fixed output. Adjustable versions have an output voltage
Adjustable version: 2% max. feedback voltage
range from 1.23V to 37V. Both versions are capable of driving
Guaranteed 3A output current
a 3A load with excellent line and load regulation.
Wide input voltage range:
These regulators are simple to use because they require a
4V to 40V
minimum number of external components and include internal
Wide output voltage range
frequency compensation and a fixed-frequency oscillator.
1.23V to 37V
The LM2576 series offers a high efficiency replacement for
Requires only 4 external components
popular three-terminal adjustable linear regulators. It
52kHz fixed frequency internal oscillator
substantially reduces the size of the heat sink, and in many
Low power standby mode I typically < 200 A
cases no heat sink is required. Q
80% efficiency (adjustable version typically > 80%)
A standard series of inductors available from several different
Uses readily available standard inductors
manufacturers are ideal for use with the LM2576 series. This
Thermal shutdown and current limit protection
feature greatly simplifies the design of switch-mode power
supplies. 100% electrical thermal limit burn-in
The feedback voltage is guaranteed to 2% tolerance for
Applications
adjustable versions, and the output voltage is guaranteed to
3% for fixed versions, within specified input voltages and
Simple high-efficiency step-down (buck) regulator
output load conditions. The oscillator frequency is guaranteed
Efficient pre-regulator for linear regulators
to 10%. External shutdown is included, featuring less than
On-card switching regulators
200 A standby current. The output switch includes cycle-by-
Positive to negative converter (inverting Buck-Boost)
cycle current limiting and thermal shutdown for full protection
Isolated Flyback Converter using minimum number of
under fault conditions.
external components
Negative Boost Converter
Typical Applications
7V40V 7V40V
Unregulated Unregulated
+5V, 1A +5V, 1A
4 4
Feedback Feedback
DC Input DC Input
1 Regulated 1 Regulated
LM2575-5.0 LM2575
L1 L1
Output Output
Output Output
+V +V
IN IN
2 2
330H 330H
+ + + + R2 3.09k
3 5 3 5
C C
IN IN
Gnd On/Off Gnd On/Off
D1 D1
C C
OUT OUT
100F 100F
R1 1k
1N5822 1N5822
330F 330F
Note: Pin numbers are for TO-220 Package Note: Pin numbers are for TO-220 Package
R2
V = 1.23 1 +
OUT ( )
R1
Fixed Regulator in Typical Application Adjustable Regulator in Fixed Output Application
Micrel, Inc. 2180 Fortune Drive San Jose, CA 95131 USA tel + 1 (408) 944-0800 fax + 1 (408) 474-1000 LM2576 Micrel, Inc.
Ordering Information
Part Number Temperature
Standard RoHS Compliant** Range Package
LM2576BT* LM2576WT* 40C to +85C TO-220-5
LM2576-3.3BT LM2576-3.3WT 40C to +85C TO-220-5
LM2576-5.0BT LM2576-5.0WT 40C to +85C TO-220-5
LM2576-12BT LM2576-12WT 40C to +85C TO-220-5
LM2576BU* LM2576WU* 40C to +85C TO-263-5
LM2576-3.3BU LM2576-3.3WU 40C to +85C TO-263-5
LM2576-5.0BU LM2576-5.0WU 40C to +85C TO-263-5
LM2576-12BU LM2576-12WU 40C to +85C TO-263-5
* Adjustable output regulators.
**RoHS compliant withhot-melting solde exemption.
Contact factory for bent or staggered leads option.
Pin Configurations
5-LEAD TO-220 (T) 5-LEAD TO-263 (U)
GND GND
5- ON/OFF 5- ON/OFF
4- FEEDBACK 4- FEEDBACK
3- GROUND 3- GROUND
2- OUTPUT 2- OUTPUT
1- V 1- V
IN IN
M9999-082605-B 2 August 2005