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LM2574YN

P1-P3P4-P6P7-P8
July 2005 1 M9999-072805
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.
Typical Application
V
IN
PWR
GND
SIG
GND
ON/
OFF
OUT
FB
LM2574
C
IN
22µF
40V MAX
UN RE G U L AT ED
DC IN
REGULATED
OU TP U T
0.5A
11DQ05
C
OU T
220µF
330µH
Figure 1. Fixed Output Regulator Circuit
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)
Micrel, Inc. • 2180 Fortune Drive • San Jose, CA 95131 • USA • tel + 1 (408) 944-0800 • fax + 1 (408) 474-1000 • http://www.micrel.com
LM2574 Micrel, Inc.
M9999-072805 2 July 2005
Pin Configuration
FB 1
SIG GND 2
ON/OFF 3
PWR GND 4
8 NC
7 OUTPUT
6 NC
5 VIN
8-Pin DIP (N)
Ordering Information
Part Number Junction
Temp. Range
Package
Standard Pb-Free
LM2574BN LM2574YN –40ºC to +85ºC 8-pin Plastic DIP
LM2574-3.3BN LM2574-3.3YN –40ºC to +85ºC 8-pin Plastic DIP
LM2574-5.0BN LM2574-5.0YN –40ºC to +85ºC 8-pin Plastic DIP
July 2005 3 M9999-072805
LM2574 Micrel, Inc.
Absolute Maximum Ratings
(1)
Maximum Supply Voltage
LM2574 ......................................................................
45V
OFF Pin Input Voltage ................................
–0.3V ≤ V ≤ V
IN
Output Voltage to Ground (Steady State) ...................... –1V
Power Dissipation ..................................... Internally Limited
Storage Temperature Range (T
S
) ............. –65°C to +150°C
Minimum ESD Rating
C = 100pF, R = 1.5kΩ ................................................
2kV
FB Pin ........................................................................
1kV
Lead Temperature (soldering, 10 sec.) ......................
260°C
Operating Ratings
(1)
Supply Voltage
LM2574 ......................................................................
40V
Temperature Range
LM2574 ...........................................–40°C ≤ T
J
≤ +125°C
Maximum Junction Temperature (T
J
.......................... 150°C
Electrical Characteristics
(2)
Specifications with standard typeface are for T
J
= 25°C, and those with boldface type apply over full Operating Temperature Range.
Unless otherwise specified, V
IN
= 12V, and I
LOAD
= 100mA.
Symbol Parameter Condition Min Typ Max Units
System Parameters, Adjustable Regulators
(3)
, Test Circuit Figure 2
V
OUT
Feedback Voltage V
IN
= 12V, I
LOAD
= 0.1A, V
OUT
= 5V 1.217 1.230 1.243 V
V
OUT
Feedback Voltage 0.1A ≤ I
LOAD
≤ 0.5A, 7V≤ V
IN
≤ 40V, 1.193 1.230 1.267 V
(LM2574) V
OUT
= 5V 1.180 1.280 V
η Efficiency V
IN
= 12V, I
LOAD
= 0.1A, V
OUT
= 5V 78 %
System Parameters, 3.3V Regulators
(3)
, Test Circuit Figure 3
V
OUT
Output Voltage V
IN
= 12V, I
LOAD
= 0.1A, V
OUT
= 3.3V 3.234 3.3 3.366 V
V
OUT
Output Voltage 0.1A ≤ I
LOAD
≤ 0.5A, 4.75V ≤ V
IN
≤ 40V, 3.168 3.3 3.432 V
(LM2574-3.3) V
OUT
= 3.3V 3.135 3.465 V
η Efficiency V
IN
= 12V, I
LOAD
= 0.1A 73 %
System Parameters, 5V Regulators
(3)
, Test Circuit Figure 3
V
OUT
Output Voltage V
IN
= 12V, I
LOAD
= 0.1A, V
OUT
= 5V 4.900 5.0 5.100 V
V
OUT
Output Voltage 0.1A ≤ I
LOAD
≤ 0.5A, 7V≤ V
IN
≤ 40V, 4.800 5.0 5.200 V
(LM2574-5.0) V
OUT
= 5V 4.750 5.250 V
η Efficiency V
IN
= 12V, I
LOAD
= 0.1A, V
OUT
= 5V 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 Charac-
teristics.”
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 Charac-
teristics.”
P1-P3P4-P6P7-P8

LM2574YN

Mfr. #:
Buy LM2574YN
Manufacturer:
Microchip Technology / Micrel
Description:
Switching Voltage Regulators 0.5A Step-Down SMPS Regulator
Lifecycle:
New from this manufacturer.
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