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LM2575
52kHz Simple 1A Buck Regulator
General Description
The LM2575 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, 12V, fixed output. Adjustable versions have an
output voltage range from 1.23V to 37V. Both versions are
capable of driving a 1A 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 LM2575 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 LM2575
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.
Data sheets and support documentation can be found on
Micrel’s web site at www.micrel.com.
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 1A 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
+5V, 1A
Regulated
Output
+
C
OUT
330µF
7V–40V
Unregulated
DC Input
1
4
LM2575
Feedback
+5V, 1A
Regulated
Output
+
C
OUT
330µF
R2 3.09k
R1 1k
+V
IN
+
C
IN
100µF
LM2575-5.0
Output L1
2
330µH
3
5
Gnd On/Off
D1
1N5822
+V
IN
+
C
IN
100µF
Output L1
2
330µH
D1
1N5822
3
5
Gnd On/Off
Note: Pin numbers are for TO-220 Package
Note: Pin numbers are for TO-220 Package
V
OUT
= 1.23 1 + R2
R1
(
)
Fixed Regulation in Typical Application
Adjustable Regulation 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
May 2009
1
M9999-051209-B
Micrel, Inc.
LM2575
Ordering Information
Part Number
Standard
LM2575BN*
LM2575-3.3BN
LM2575-5.0BN
LM2575-12BN
LM2575BWM*
LM2575-3.3BWM
LM2575-5.0BWM
LM2575-12BWM
LM2575BT*
†
Pb-Free /
RoHS Compliant
Contact Factory
Contact Factory
LM2575-5.0YN
LM2575-12YN
LM2575YWM*
LM2575-3.3YWM
LM2575-5.0YWM
LM2575-12YWM
LM2575WT*/**
LM2575-3.3WT**
LM2575-5.0WT**
LM2575-12WT**
LM2575WU*/**
LM2575-3.3WU**
LM2575-5.0WU**
LM2575-12WU**
Temperature Range
–40° to +85°C
–40° to +85°C
–40° to +85°C
–40° to +85°C
–40° to +85°C
–40° to +85°C
–40° to +85°C
–40° to +85°C
–40° to +85°C
–40° to +85°C
–40° to +85°C
–40° to +85°C
–40° to +85°C
–40° to +85°C
–40° to +85°C
–40° to +85°C
Package
16-Pin Plastic DIP
16-Pin Plastic DIP
16-Pin Plastic DIP
16-Pin Plastic DIP
24-Pin Wide SOIC
24-Pin Wide SOIC
24-Pin Wide SOIC
24-Pin Wide SOIC
5-Pin TO-220
5-Pin TO-220
5-Pin TO-220
5-Pin TO-220
5-Pin TO-263
5-Pin TO-263
5-Pin TO-263
5-Pin TO-263
LM2575-3.3BT
†
LM2575-5.0BT
†
LM2575-12BT
†
LM2575BU*
LM2575-3.3BU
LM2575-5.0BU
LM2575-12BU
Notes:
*
**
†
Adjustable output regulators.
RoHS compliant with "high-melting solder" exemption.
Contact factory for bent or staggered leads option.
May 2009
2
M9999-051209-B
Micrel, Inc.
LM2575
Pin Configuration
5 ON/OFF
4 FB
3 GND
2 OUT
1 VIN
5-Pin TO-220 (T)
5
4
3
2
1
5-Pin TO-263 (U)
ON/OFF
FB
GND
OUT
VIN
TAB
TAB
PWR GND
NC
NC
NC
1
2
3
4
5
6
7
8
9
24 NC
23 NC
22 NC
21 NC
20 NC
19 NC
18 OUT
17 OUT
16 NC
15 VIN
14 VIN
13 NC
24-Pin Wide SOIC (WM)
NC 1
NC 2
OUT 3
NC 4
GND 5
NC 6
FB 7
NC 8
16 VIN
15 NC
14 GND
13 GND
12 GND
11 GND
10 NC
9 ON/OFF
NC
NC
FB
SIG GND
NC
ON/OFF 10
NC 11
PWR GND 12
16-Pin Plastic DIP (N)
May 2009
3
M9999-051209-B
Micrel, Inc.
LM2575
Absolute Maximum Ratings
(1)
Maximum Supply Voltage (V
IN
) ......................................45V
ON/OFF Pin Input Voltage. ......................–0.3V
≤
V
≤
+40V
Output Voltage to Ground (Steady State) ......................–1V
Power Dissipation .....................................Internally Limited
Maximum Junction Temperature................................ 150°C
Lead Temperature (soldering, 10 sec.)...................... 260°C
Storage Temperature (T
s
) .........................–65°C to +150°C
Minimum ESD Rating
C = 100pF, R = 1.5kΩ.............................................. 2kV
FB Pin ...................................................................... 1kV
Operating Ratings
Supply Voltage (V
IN
).......................................................40V
Junction Temperature Range (T
J
).......–40°C
≤
T
J
≤
+125°C
Electrical Characteristics
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
= 200mA.
LM2575
Limit
(Note 2)
Units
(Limits)
Symbol
Parameter
Condition
SYSTEM PARAMETERS, ADJUSTABLE REGULATORS (Note 3)
Test Circuit Figure 1
Typ
Feedback Voltage
V
OUT
V
IN
= 12V , I
LOAD
= 0.2A
V
OUT
= 5V
0.2A
≤
I
LOAD
≤
1A, 8V
≤
V
IN
≤
40V
V
OUT
= 5V
1.230
1.217
1.243
1.230
1.193/
1.180
1.267/
1.280
82
3.3
3.234
3.366
3.3
3.168/
3.135
3.432/
3.465
75
5.0
4.900
5.100
5.0
4.800/
4.750
5.200/
5.250
82
12
11.760
12.240
12
11.520/
11.400
12.480/
12.600
88
Feedback Voltage LM2575
η
Efficiency
V
IN
= 12V, I
LOAD
= 1A, V
OUT
= 5V
SYSTEM PARAMETERS, 3.3V REGULATORS (Note 3)
Test Circuit Figure 1
Output Voltage
V
OUT
V
IN
= 12V , I
LOAD
= 0.2A
V
OUT
= 3.3V
0.2A
≤
I
LOAD
≤
1A, 8V
≤
V
IN
≤
40V
V
OUT
= 3.3V
V
V(min)
V(max)
V
V(min)
V(max)
%
V
V(min)
V(max)
V
V(min)
V(max)
%
V
V(min)
V(max)
V
V(min)
V(max)
%
V
V(min)
V(max)
V
V(min)
V(max)
%
Output Voltage LM2575-3.3
η
Efficiency
V
IN
= 12V, I
LOAD
= 1A
SYSTEM PARAMETERS, 5V REGULATORS (Note 3)
Test Circuit Figure 1
Output Voltage
V
OUT
V
IN
= 12V , I
LOAD
= 0.2A
V
OUT
= 5V
0.2A
≤
I
LOAD
≤
1A, 8V
≤
V
IN
≤
40V
V
OUT
= 5V
Output Voltage LM2575-5.0
η
Efficiency
V
IN
= 12V, I
LOAD
= 1A
SYSTEM PARAMETERS, 12V REGULATORS (Note 3)
Test Circuit Figure 1
Output Voltage
V
OUT
V
IN
= 25V , I
LOAD
= 0.2A
V
OUT
= 12V
0.2A
≤
I
LOAD
≤
1A, 15V
≤
V
IN
≤
40V
V
OUT
= 12V
V
IN
= 25V, I
LOAD
= 1A
Output Voltage LM2575-12
η
Efficiency
May 2009
4
M9999-051209-B
Analog electronics
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