MICREL LM2574YN

LM2574
Micrel, Inc.
LM2574
52kHz Simple 0.5A Buck Regulator
General Description
Features
The LM2574 family is a series of easy to use fixed and adjustable 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 versions, 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 cycleby-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.
• 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
Typical Application
40V MAX
UNREGULATED
DC IN
•
•
•
•
330µH
LM2574
PWR
GND
Simple high-efficiency step-down (buck) regulator
Efficient pre-regulator for linear regulators
On-card switching regulators
Positive to negative converter (buck-boost)
FB
VIN
CIN
22µF
Applications
OUT
SIG ON/
GND OFF
11DQ05
REGULATED
OUTPUT
0.5A
COU 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
LM2574
Micrel, Inc.
Ordering Information
Part Number
Junction
Temp. Range
Package
LM2574YN
–40ºC to +85ºC
8-pin Plastic DIP
LM2574-3.3YN
–40ºC to +85ºC
8-pin Plastic DIP
LM2574-5.0YN
–40ºC to +85ºC
8-pin Plastic DIP
Standard
Pb-Free
LM2574BN
LM2574-3.3BN
LM2574-5.0BN
Pin Configuration
8 NC
FB 1
7 OUTPUT
SIG GND 2
ON/OFF 3
6 NC
PWR GND 4
5 VIN
8-Pin DIP (N)
M9999-072805
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July 2005
LM2574
Micrel, Inc.
Absolute Maximum Ratings(1)
Operating Ratings(1)
Maximum Supply Voltage
LM2574...................................................................... 45V
OFF Pin Input Voltage ................................ –0.3V ≤ V ≤ VIN
Output Voltage to Ground (Steady State) ...................... –1V
Power Dissipation ..................................... Internally Limited
Storage Temperature Range (TS) ............. –65°C to +150°C
Minimum ESD Rating
C = 100pF, R = 1.5kΩ ................................................ 2kV
FB Pin ........................................................................ 1kV
Lead Temperature (soldering, 10 sec.) ...................... 260°C
Supply Voltage
LM2574...................................................................... 40V
Temperature Range
LM2574...........................................–40°C ≤ TJ ≤ +125°C
Maximum Junction Temperature (TJ.......................... 150°C
Electrical Characteristics(2)
Specifications with standard typeface are for TJ = 25°C, and those with boldface type apply over full Operating Temperature Range.
Unless otherwise specified, VIN = 12V, and ILOAD = 100mA.
Symbol
Parameter
Condition
System Parameters, Adjustable
VOUT
Feedback Voltage
VOUT
Feedback Voltage
(LM2574)
η
Efficiency
System Parameters, 3.3V
VOUT
Regulators(3),
Regulators(3),
Output Voltage
VOUT
Output Voltage
(LM2574-3.3)
η
Efficiency
Min
Typ
Max
Units
1.217
1.230
1.243
V
1.193
1.180
1.230
1.267
1.280
V
V
Test Circuit Figure 2
VIN = 12V, ILOAD = 0.1A, VOUT = 5V
0.1A ≤ ILOAD ≤ 0.5A, 7V≤ VIN ≤ 40V,
VOUT = 5V
VIN = 12V, ILOAD = 0.1A, VOUT = 5V
78
%
Test Circuit Figure 3
VIN = 12V, ILOAD = 0.1A, VOUT = 3.3V
0.1A ≤ ILOAD ≤ 0.5A, 4.75V ≤ VIN ≤ 40V,
VOUT = 3.3V
3.234
3.3
3.366
V
3.168
3.135
3.3
3.432
3.465
V
V
VIN = 12V, ILOAD = 0.1A
73
%
System Parameters, 5V Regulators(3), Test Circuit Figure 3
VOUT
Output Voltage
VOUT
Output Voltage
(LM2574-5.0)
η
Efficiency
VIN = 12V, ILOAD = 0.1A, VOUT = 5V
0.1A ≤ ILOAD ≤ 0.5A, 7V≤ VIN ≤ 40V,
VOUT = 5V
VIN = 12V, ILOAD = 0.1A, VOUT = 5V
4.900
5.0
5.100
V
4.800
4.750
5.0
5.200
5.250
V
V
78
%
Notes:
1. “Absolute Maximum Ratings” indicate limits beyond which damage to the device may occur. “Operating Ratings” indicate for which the device is
intended to be functional, but do not guarantee specific performance limits. For guaranteed specifications and test conditions, see “Electrical Characteristics.”
2. 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 extremes are guaranteed via testing.
3. External components such as the catch diode, inductor, input and output capacitors can affect switching regulator system performance.
When the LM2574 is used as shown in Figure 1 test circuit, system performance will be shown in system parameters section of “Electrical Characteristics.”
July 2005
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M9999-072805
LM2574
Micrel, Inc.
Electrical Characteristics
Symbol
Parameter
Condition
Min
Typ
Max
Units
50
100
500
nA
nA
52
58
63
kHz
kHz
0.8
1.2
1.4
V
V
Device Parameters, Adjustable Regulator
IB
Feedback Bias Current
VOUT = 5V
Device Parameters, Fixed and Adjustable Regulators
fo
Oscillator Frequency
Note 8
VSAT
Saturation Voltage
IOUT = 0.5A(4)
47
42
DC
Max Duty Cycle (ON)
Note 5
ICL
Current Limit
Peak Current, tON ≤ 3µs(4)
IL
Output Leakage Current
VIN, Note 6, Output = 0V
Note 6, Output = –1V
IQ
ISTBY
93
98
0.7
0.65
1.0
7.5
%
1.6
1.8
A
2
30
mA
Quiescent Current
Note 6
5
10
mA
Standby Quiescent Current
ON/OFF Pin = 5V (OFF)
50
200
µA
θJA
Thermal Resistance
N Package, Junction
VIH
ON/OFF Input Level
VOUT = 0V
VIL
ON/OFF Input Level
VOUT = 5V
IIH
ON/OFF Logic Current
ON/OFF Logic Current
to Ambient(7)
85
°C/W
1.4
V
V
On/Off Control, Fixed and Adjustable Regulators Test Circuit Figures 2, 3
IIL
2.2
2.4
1.2
1.0
0.8
V
V
ON/OFF = 5V (OFF)
4
30
µA
ON/OFF = 0V (ON)
0.01
10
µA
Notes:
4. Output (pin 2) sourcing current. No diode, inductor, or capacitor connected to input.
5. Feedback (pin 4) removed from output and connected to 0V.
6. Feedback (pin 4) removed from output and connected to 12V to force the output transistor OFF.
7. Junction-to-ambient thermal resistance with approximately 1 square inches of PC board copper surrounding the leads.
Test Circuit
FB
VIN
CIN
22µF
LM2574
(adjustable)
OUT
PWR
SIG
ON/
GND GND OFF
330µH
11DQ06
COU T
220µF
3.09k
1k
Figure 2. Adjustable Regulator Test Circuit
VIN
CIN
22µF
FB
LM2574–
3.3, 5, 12
OUT
P W R S I G ON/
GND GND O F F
330µH
11DQ06
COU T
220µF
Figure 3. Fixed Regulator Test Circuit
M9999-072805
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July 2005
LM2574
Micrel, Inc.
Typical Characteristics (Circuit of Figure 1)
Supply Current
vs. Duty Cycle
Supply Current
20
20.0
Measured at
Ground Pin
TJ = 25˚C
VOUT = 5V
18
16
12
10.0
10
I LO AD = 100 mA
VIN from 7V to 40V
2.5
10
20
30
40
50
60
0
0
20
INPUT VOLTAGE ( V)
V IN = 25V
40
60
80
100
D U TY C YC LE ( % )
JU N C TI O N TEM PER ATU R E ( ˚ C )
Efficiency
100
1.1
-55˚C
-40˚C
0.7
0
0.1
0.2
0.3
0.4
0.5
60
Line Regulation
3.5
8
3.0
6
2.5
4
0
2.0
2
-25
100
75
50
25
Normalized
Output Voltage
VIN = 12V
I LO AD = 100mA
Normalized toTJ = 25˚C
VOUT = 5V
25
-75
5
10
15
20
25
INPUT VOLTAGE ( V)
30
-100
-75 -50 -25 0 25 50 75 100 125150
JU N C TI O N TEM PER ATU R E ( ˚ C )
Oscillator Frequency
Normalized at 25˚ C
+4
2.0
1.5
Dropout Voltage
I LO AD = 0.5A
∆VOUT = 5%
R IND = 0.2Ω
+2
0
-2
-50
-4
-75
--6
JU N C TI O N TEM PER ATU R E ( ˚ C )
50
-50
0
0
25 50 75 100125150
35 40
75
-6
-25
-100
-75 -50 -25 0
Normalized toVIN = 10V
VOUT = 5V
ILO AD = 100mA
TJ = 25
0
+6
10 15 20 25 30
100
-2
-4
+8
5
Feedback Pin Current
10
0.5
0
-75 -50 -25 0 25 50 75 100125150
J U N C TI O N TEM PER ATU R E ( ˚ C )
0
INPUT VOLTAGE ( V)
4.0
VOUT = 1.23V
I LO AD = 100 mA
VOUT = 3V
65
14
12
1.0
0.5A
70
5.0
4.5
1.5
100 mA
75
SW I TC H C U R R EN T ( A)
Minimum Operating
Voltage
100 mA
80
25˚C
JU N C TI O N TEM PER ATU R E ( ˚ C )
July 2005
85
0.5 125˚C
150˚C
0.3
0.5A
90
1
0
-75 -50 -25 0 25 50 75 100125 150
VOUT = 12V
95
0.9
0.5
0
-75 -50 -25 0 25 50 75 100 125150
Switch
Saturation Voltage
Current Limit
1.5
VIN = 12V
50
5.0
6
VON/OFF = 5V
100
7.5
I LO AD to 0.5A
0
VIN = 40V
150
15.0
12.5
4
200
17.5
14
8
Standby
Quiescent Current
1.0
VIN = 40V
0.5
I LO AD = 100 mA
VIN = 12V
-8
-75 -50 -25 0 25 50 75 100125150
0
-75 -50 -25 0 25 50 75 100125150
J U N C TI O N TEM PER ATU R E ( ˚ C )
JU N C TI O N TEM PER ATU R E ( ˚ C )
5
M9999-072805
LM2574
Micrel, Inc.
Typical Performance Characteristics (continued)
25
20
15
10
5
Normalized
Feedback Voltage*
Feedback Voltage
vs Duty Cycle*
20
VIN = 12V
I LO AD = 100mA
Normalized toTJ = 25˚ C
I LO AD = 100 mA
15
10
5
0
VIN = 40V
0
-5
-10
-5
VIN = 7V
-10
-15
-20
-25
-75 -50 -25 0
-15
-20
25 50 75 100125150
JU N C TI O N TEM PER ATU R E ( ˚ C )
0
20
40
60
80
100
D U TY C YC LE ( % )
* Adjustable version only
M9999-072805
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July 2005
LM2574
Micrel, Inc.
Block Diagrams
V IN
1
F EED BACK
4
INTERNAL
REGULATOR
1.23V
BAND-GAP
REFERENCE
ON/OFF
V IN
INTERNAL
REGULATOR
1
+
-
F EED BACK
1/2 AMP
SW ITCH
COM PARAT OR
+
-
52 kHz
OSCILLATOR
ON/OFF
5
ON/OFF
2
OUTPUT
3
GND
FIXED GAIN
E R R OR A M P
FIXED GAIN
E R R OR A M P
3.1k
1.0k
5
ON/OFF
4
+
-
DRIVER
2
RESET
THERMAL
SHUTDOWN
CURRENT
LIMIT
3
1/2 AMP
SW ITCH
COM PARAT OR
+
-
DRIVER
OUTPUT
1.23V
BAND-GAP
REFERENCE
GND
52 kHz
OSCILLATOR
RESET
THERMAL
SHUTDOWN
CURRENT
LIMIT
Note: Pin numbers are for the TO-220 package
Fixed Regulator
July 2005
Adjustable Regulator
7
M9999-072805
LM2574
Micrel, Inc.
Package Information
PIN 1
DIMENSIONS:
INCH (MM)
0.380 (9.65)
0.370 (9.40)
0.255 (6.48)
0.245 (6.22)
0.135 (3.43)
0.125 (3.18)
0.300 (7.62)
0.013 (0.330)
0.010 (0.254)
0.018 (0.57)
0.130 (3.30)
0.100 (2.54)
0.0375 (0.952)
0.380 (9.65)
0.320 (8.13)
8-Pin DIP (N)
MICREL INC.
TEL
2180 FORTUNE DRIVE
SAN JOSE, CA 95131
USA
+ 1 (408) 944-0800 FAX + 1 (408) 474-1000 WEB http://www.micrel.com
This information furnished by Micrel in this data sheet is believed to be accurate and reliable. However no responsibility is assumed by Micrel for its use.
Micrel reserves the right to change circuitry and specifications at any time without notification to the customer.
Micrel Products are not designed or authorized for use as components in life support appliances, devices or systems where malfunction of a product can
reasonably be expected to result in personal injury. Life support devices or systems are devices or systems that (a) are intended for surgical implant into
the body or (b) support or sustain life, and whose failure to perform can be reasonably expected to result in a significant injury to the user. A Purchaser's
use or sale of Micrel Products for use in life support appliances, devices or systems is a Purchaser's own risk and Purchaser agrees to fully indemnify
Micrel for any damages resulting from such use or sale.
© 2003 Micrel, Inc.
M9999-072805
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July 2005