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PDF LM2576 Data sheet ( Hoja de datos )
| Número de pieza | LM2576 | |
| Descripción | 52kHz Simple 3A Buck Voltage Regulator | |
| Fabricantes | Micrel Semiconductor | |
| Logotipo |  |
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LM2576
LM2576
Micrel, Inc.
52kHz Simple 3A Buck 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 ±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.
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 3A 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
+VIN LM2575-5.0 Output L1
+5V, 1A
Regulated
Output
+
CIN
100µF
3 52
Gnd On/Off
330µH
D1
1N5822
+
COUT
330µF
Note: Pin numbers are for TO-220 Package
Fixed Regulator in Typical Application
7V–40V
Unregulated
DC Input
1
+VIN
LM2575
+
CIN
100µF
35
Gnd On/Off
4 Feedback
Output L1
2 330µH
D1
1N5822
+
COUT
330µF
+5V, 1A
Regulated
Output
R2 3.09k
R1 1k
Note: Pin numbers are for TO-220 Package
( )VOUT = 1.23
1
+
R2
R1
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 • http://www.micrel.com
August 2005
1 M9999-082605-B
1 page  
LM2576
Electrical Characteristics (continued)
Micrel, Inc.
LM2576
Units
Symbol Parameter
Conditions
Typ Limit
(Note 2)
(Limits)
ON/OFF CONTROL, FIXED and ADJUSTABLE REGULATORS Test Circuit Figure 1
VIH
ON/OFF Pin Logic
VOUT = 0V
VIL Input Level
VOUT = 5V
IIH
ON /OFF Pin Logic
ON /OFF Pin = 5V (OFF)
Current
1.4 2.2/2.4
1.2 1.0/0.8
4
30
V(min)
V(max)
µA
µA(max)
IIL
ON/OFF Pin = 0V (ON)
0.01
µA
10 µA(max)
Note 1:
Note 2:
Note 3:
Note 4:
Note 5:
Note 6:
Note 7:
Note 8:
Note 9:
Absolute Maximum Rating indicate limits beyond which damage to the device may occur. Operating Ratings indicate conditions for which the device
is intended to be functional, but do not guarantee specific performance limits. For guaranteed specifications and test conditions, see the Electrical
Characteristics.
All limits guaranteed at room temperature (standard type face) and at temperature extremes (bold type face) . All room temperature limits are
100% production tested. All limits at temperature extreme are guaranteed via testing.
External components such as the catch diode, inductor, input and output capacitors can affect switching regulator system performance. When the
LM2576/LM1576 is used as shown in Figure 1 test circuit, system performance will be shown in system parameters section of Electrical
Characteristics.
Output (pin 2) sourcing current. No diode, inductor or capacitor connected to output.
Feedback (pin 4) removed from output and connected to 0V.
Feedback (pin 4) removed from output and connected to 12V to force the output transistor OFF.
Junction to ambient thermal resistance (no external heat sink) for the 5-lead TO-220 package mounted vertically, with 1/2" leads in a socket, or
on PC board with minimum copper area.
Junction to ambient thermal resistance (no external heat sink) for the 5-lead TO-220 package mounted vertically, with 1/4" leads soldered to PC
board containing approximately 4 square inches of copper area surrounding the leads.
Junction to ambient thermal resistance with approximately 1 square inch of pc board copper surrounding the leads. Additional copper will lower
thermal resistance further.
Typical Performance Characteristics
Normalized
Feedback Voltage*
25
20 VIN = 12V
15
10
ILOAD = 200mA
Normalized to TJ = 25˚C
5
0
-5
-10
-15
-20
-25
-75 -50 -25 0 25 50 75 100 125 150
JUNCTION TEMPERATURE (˚C)
Feedback Voltage
vs Duty Cycle*
20
ILOAD = 200 mA
15
10
5 VIN = 40V
0
-5
VIN = 7V
-10
-15
-20
0
20 40 60 80
DUTY CYCLE (%)
100
* Adjustable version only
August 2005
5 M9999-082605-B
5 Page | ||
| Páginas | Total 9 Páginas | |
| PDF Descargar | [ Datasheet LM2576.PDF ] | |
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