MICREL LM2574BN, LM2574-5.0BWM, LM2574-5.0BN, LM2574-3.3BWM, LM2574-12BWM Datasheet
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LM2574 Micrel
LM2574
52kHz Simple 0.5A Buck Regulator
General Description
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, 5V, and 12V 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 cycle-bycycle 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.
Pin Configuration
FB 1
SIG GND 2
ON/OFF 3
PWR GND 4
*1
*2
FB 3
SIG GND 4
ON/OFF 5
PWR GND 6
*7
8-pin DIP (N)
8*
7 OUTPUT
6*
5V
IN
14 *
13 *
12 OUTPUT
11 *
10 V
IN
9*
8*
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)
Ordering Information
Part Number Temp. Range Package
LM2574BN –40°C to +85°C 8-pin Plastic DIP
LM2574BWM –40°C to +85°C 14-pin Wide SOIC
LM2574-3.3BN –40°C to +85°C 8-pin Plastic DIP
LM2574-3.3BWM –40°C to +85°C 14-pin Wide SOIC
LM2574-5.0BN –40°C to +85°C 8-pin Plastic DIP
LM2574-5.0BWM –40°C to +85°C 14-pin Wide SOIC
LM2574-12BN –40°C to +85°C 8-pin Plastic DIP
LM2574-12BWM –40°C to +85°C 14-pin Wide SOIC
Typical Application
40V MAX
UNREGULATED
DC IN
C
IN
22µF
V
IN
PWR
GND
LM2574
SIG
GND
OUT
ON/
OFF
FB
330µH
11DQ05
REGULATED
OUTPUT
0.5A
C
OUT
220µF
14-pin SOIC (WM)
* NC: solder to printed circuit for
maximum heat transfer
Figure 1. Fixed Output Regulator Circuit
August 1999 1 LM2574
LM2574 Micrel
Absolute Maximum Ratings
Maximum Supply Voltage
LM2574 .....................................................................45V
OFF Pin Input Voltage................................ –0.3V ≤ V ≤ V
Output Voltage to Ground (Steady State) .....................–1V
Operating Ratings
Temperature Range
LM2574 ........................................... 40°C ≤ TJ ≤ +125°C
Supply Voltage
IN
LM2574 .....................................................................40V
Power Dissipation .................................... Internally Limited
Storage Temperature Range ................... –65°C to +150°C
Minimum ESD Rating
C = 100pF, R = 1.5kΩ ............................................... 2kV
FB Pin ....................................................................... 1kV
Lead Temperature (soldering, 10 sec.) ..................... 260°C
Maximum Junction Temperature............................... 150°C
Electrical Characteristics Specifications with standard typeface are for T
over full Operating Temperature Range. Unless otherwise specified, V
Symbol Parameter Condition Min Typ Max Units
SYSTEM PARAMETERS, ADJUSTABLE REGULATORS (Note 3) Test Circuit
V
V
OUT
OUT
Feedback Voltage V
= 12V, I
IN
Feedback Voltage 0.1A ≤ I
LOAD
≤ 0.5A, 7V≤ VIN ≤ 40V, V
LOAD
(LM2574) 1.180 1.280 V
η Efficiency VIN = 12V, I
LOAD
SYSTEM PARAMETERS, 3.3V REGULATORS (Note 3) Test Circuit
V
OUT
V
OUT
η Efficiency VIN = 12V, I
Output Voltage VIN = 12V, I
Output Voltage 0.1A ≤ I
(LM2574-3.3) V
LOAD
= 3.3V 3.135 3.465 V
OUT
LOAD
≤ 0.5A, 4.75V ≤ VIN ≤ 40V, 3.168 3.3 3.432 V
LOAD
SYSTEM PARAMETERS, 5V REGULATORS (Note 3) Test Circuit
V
OUT
V
OUT
η Efficiency VIN = 12V, I
Output Voltage VIN = 12V, I
Output Voltage 0.1A ≤ I
(LM2574-5.0) V
LOAD
= 5V 4.750 5.250 V
OUT
LOAD
≤ 0.5A, 7V≤ VIN ≤ 40V, 4.800 5.0 5.200 V
LOAD
SYSTEM PARAMETERS, 12V REGULATORS (Note 3) Test Circuit
V
OUT
V
OUT
η Efficiency VIN = 25V, I
Output Voltage VIN = 25V, I
Output Voltage 0.1A ≤ I
(LM2574-12) V
LOAD
= 12V 11.400 12.600 V
OUT
LOAD
≤ 0.5A, 15V ≤ VIN ≤ 40V, 11.520 12 12.480 V
LOAD
= 12V, and I
in
Figure 2
= 0.1A, V
= 0.1A, V
= 5V 1.217 1.230 1.243 V
OUT
= 5V 78 %
OUT
Figure 3
= 0.1A, V
= 3.3V 3.234 3.3 3.366 V
OUT
= 0.1A 73 %
Figure 3
= 0.1A, V
= 0.1A, V
= 5V 4.900 5.0 5.100 V
OUT
= 5V 78 %
OUT
Figure 3
= 0.1A, V
= 12V 11.760 12 12.240 V
OUT
= 0.1A 88 %
= 25°C, and those with boldface type apply
J
= 100mA.
LOAD
= 5V 1.193 1.230 1.267 V
OUT
LM2574 2 August 1999
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