LM2576
Micrel
LM2576
52kHz Simple 3A Buck Voltage Regulator
General Description
The LM2576 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, or 12V
fixed output. Adjustable versions have an output voltage
range from 1.23V to 37V. Both versions are capable of driving
a 3A 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 LM2576 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 LM2576 series. This
feature greatly simplifies the design of switch-mode power
supplies.
The feedback voltage is guaranteed to
鹵2%
tolerance for
adjustable versions, and the output voltage is guaranteed to
鹵3%
for fixed versions, within specified input voltages and
output load conditions. The oscillator frequency is guaranteed
to
鹵10%.
External shutdown is included, featuring less than
200碌A(chǔ) standby current. The output switch includes cycle-by-
cycle current limiting and thermal shutdown for full protection
under fault conditions.
Features
鈥?3.3V, 5V, 12V, and adjustable output versions
鈥?Voltage over specified line and load conditions:
Fixed version:
鹵3%
max. output voltage
Adjustable version:
鹵2%
max. feedback voltage
鈥?Guaranteed 3A output current
鈥?Wide input voltage range:
4V to 40V
鈥?Wide output voltage range
1.23V to 37V
鈥?Requires only 4 external components
鈥?52kHz fixed frequency internal oscillator
鈥?Low power standby mode I
Q
typically < 200碌A(chǔ)
鈥?80% efficiency (adjustable version typically > 80%)
鈥?Uses readily available standard inductors
鈥?Thermal shutdown and current limit protection
鈥?100% electrical thermal limit burn-in
Applications
鈥?/div>
鈥?/div>
鈥?/div>
鈥?/div>
鈥?/div>
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
鈥?Negative Boost Converter
Typical Applications
870 20
7V鈥?0V
Unregulated
DC Input
+V
IN
C
IN
100碌F
+
LM2576-5.0 Output L1
2
100碌H
3
5
Gnd On/Off
D1
1N5822
1
4
Feedback
+5V, 3A
Regulated
Output
+
C
OUT
1000碌F
7V鈥?0V
Unregulated
DC Input
1
4
LM2576
Feedback
+V
IN
C
IN
100碌F
+
Output L1
2
100碌H
D1
1N5822
+
C
OUT
1000碌F
+5V, 3A
Regulated
Output
R2 3.09k
R1 1k
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 Regulator in Typical Application
Adjustable Regulator in Fixed Output Application
4-120
October 1998
LM2576-5.0BU相關(guān)型號(hào)PDF文件下載
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