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PDF LM2574 Data sheet ( Hoja de datos )
| Número de pieza | LM2574 | |
| Descripción | 52kHz Simple 0.5A Buck Regulator | |
| Fabricantes | Micrel Semiconductor | |
| Logotipo |  |
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LM2574
Micrel, Inc.
LM2574
52kHz Simple 0.5A Buck Regulator
General Description
The LM2574 family is a series of easy to use fixed and ad-
justable switching voltage regulators. The LM2574 contains
all of the active circuitry necessary to construct a stepdown
(buck) switching regulator and requires a minimum of external
components.
The LM2574 is available in 3.3V and 5V fixed output ver-
sions, or an adjustable version with an output voltage range
of 1.23V to 37V. Output voltage is guaranteed to ±4% for
specified input and load conditions.
The LM2574 can supply 0.5A while maintaining excellent
line and load regulation. The output switch includes cycle-
by-cycle current limiting, as well as thermal shutdown for full
protection under fault conditions.
An external shutdown connection selects operating or standby
modes. Standby current is less than 200µA.
Heat sinks are generally unnecessary due the regulator’s
high efficiency. Adequate heat transfer is usually provided
by soldering all package pins to a printed circuit board.
The LM2574 includes internal frequency compensation and
an internal 52kHz fixed frequency oscillator guaranteed to
±10% of the frequency.
Circuits constructed around the LM2574 use a standard
series of inductors which are available from several different
manufacturers.
All support documentation can be found on Micrel’s web site
at www.micrel.com.
Features
• 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
• 52kHz fixed frequency internal oscillator
• Uses standard inductors
Applications
• Simple high-efficiency step-down (buck) regulator
• Efficient pre-regulator for linear regulators
• On-card switching regulators
• Positive to negative converter (buck-boost)
Typical Application
40V MAX
UNREGULATED
DC IN
CIN
22µF
FB
VIN
LM2574
OUT
PWR SIG ON/
GND GND OFF
330µH
REGULATED
OUTPUT
0.5A
11DQ05
CO U T
220µF
Figure 1. Fixed Output Regulator Circuit
Micrel, Inc. • 2180 Fortune Drive • San Jose, CA 95131 • USA • tel + 1 (408) 944-0800 • fax + 1 (408) 474-1000 • http://www.micrel.com
July 2005
1 M9999-072805
1 page  
LM2574
Typical Characteristics (Circuit of Figure 1)
Supply Current
20 Measured at
18 Ground Pin
TJ = 25˚C
16 VOUT = 5V
14
12
10
8 ILOADto 0.5A
6
4
0 10 20 30 40 50 60
INPUT VOLTAGE (V)
Current Limit
1.5
V IN = 25V
1
0.5
0
-75 -50 -25 0 25 50 75 100125 150
JUNCTION TEMPERATURE (˚C)
Minimum Operating
Voltage
5.0
4.5
4.0
3.5
3.0
2.5
2.0
1.5
1.0 VOUT = 1.23V
0.5 I LO AD = 100 mA
0
-75 -50 -25 0 25 50 75 100125150
JUNCTION TEMPERATURE (˚C)
20.0
17.5
15.0
12.5
10.0
7.5
5.0
2.5
0
0
Supply Current
vs. Duty Cycle
ILOAD= 100 mA
VIN from 7V to 40V
20 40 60 80
DUTY CYCLE (%)
100
Switch
Saturation Voltage
1.1
0.9
-55˚C
-40˚C
0.7 25˚C
0.5 125˚C
150˚C
0.3
0
0.1 0.2 0.3 0.4
SWITCH CURRENT (A)
0.5
Line Regulation
14
12 Normalized toVIN = 10V
10 VOUT = 5V
8
6
ILO AD = 100mA
TJ = 25
4
2
0
-2
-4
-6
0 5 10 15 20 25
INPUT VOLTAGE (V)
30
Normalized
Output Voltage
100
VIN = 12V
75 ILOAD= 100mA
50 Normalized toTJ = 25˚C
VOUT = 5V
25
0
-25
-50
-75
-100
-75 -50 -25 0 25 50 75 100125150
JUNCTION TEMPERATURE (˚C)
Oscillator Frequency
+8
Normalized at 25˚ C
+6
+4
+2
0
-2
VIN = 40V
-4
--6
VIN = 12V
-8
-75 -50 -25 0 25 50 75 100125150
JUNCTION TEMPERATURE (˚C)
Micrel, Inc.
Standby
Quiescent Current
200
VIN = 40V
150
VON/OFF= 5V
100
VIN = 12V
50
0
-75 -50 -25 0 25 50 75 100 125150
JUNCTION TEMPERATURE (˚C)
Efficiency
100
95 VOUT = 12V
90 0.5A
85 100 mA
80
100 mA
75 0.5A
70 VOUT = 3V
65
60
0
5 10 15 20 25 30 35 40
INPUT VOLTAGE (V)
Feedback Pin Current
100
75
50
25
0
-25
-50
-75
-100
-75 -50 -25 0 25 50 75 100 125150
JUNCTION TEMPERATURE (˚C)
Dropout Voltage
2.0
∆VOUT = 5%
ILOAD= 0.5A
1.5
RIND = 0.2Ω
1.0
ILOAD= 100 mA
0.5
0
-75 -50 -25 0 25 50 75 100125150
JUNCTION TEMPERATURE (˚C)
July 2005
5 M9999-072805
5 Page | ||
| Páginas | Total 8 Páginas | |
| PDF Descargar | [ Datasheet LM2574.PDF ] | |
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