MICREL LM2575

LM2575
52kHz Simple 1A Buck Regulator
General Description
Features
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 switchmode 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.
• 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
LM2575-5.0 Output L1
2
330µH
3
5
Gnd On/Off
D1
1N5822
+VIN
+
CIN
100µF
7V–40V
Unregulated
DC Input
+5V, 1A
Regulated
Output
Feedback
1
+VIN
+
CIN
100µF
+
COUT
330µF
4
LM2575
3
5
Gnd On/Off
+5V, 1A
Regulated
Output
Feedback
Output L1
2
330µH
D1
1N5822
+
R2 3.09k
COUT
330µF
R1 1k
Note: Pin numbers are for TO-220 Package
Note: Pin numbers are for TO-220 Package
(
VOUT = 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
Pb-Free /
RoHS Compliant
Standard
Temperature Range
Package
LM2575BN*
Contact Factory
–40° to +85°C
16-Pin Plastic DIP
LM2575-3.3BN
Contact Factory
–40° to +85°C
16-Pin Plastic DIP
LM2575-5.0BN
LM2575-5.0YN
–40° to +85°C
16-Pin Plastic DIP
LM2575-12BN
LM2575-12YN
–40° to +85°C
16-Pin Plastic DIP
LM2575BWM*
LM2575YWM*
–40° to +85°C
24-Pin Wide SOIC
LM2575-3.3BWM
LM2575-3.3YWM
–40° to +85°C
24-Pin Wide SOIC
LM2575-5.0BWM
LM2575-5.0YWM
–40° to +85°C
24-Pin Wide SOIC
LM2575-12BWM
LM2575-12YWM
–40° to +85°C
24-Pin Wide SOIC
LM2575BT*†
LM2575WT*/**
–40° to +85°C
5-Pin TO-220
LM2575-3.3BT
†
LM2575-3.3WT**
–40° to +85°C
5-Pin TO-220
LM2575-5.0BT
†
LM2575-5.0WT**
–40° to +85°C
5-Pin TO-220
LM2575-12BT†
LM2575-12WT**
–40° to +85°C
5-Pin TO-220
LM2575BU*
LM2575WU*/**
–40° to +85°C
5-Pin TO-263
LM2575-3.3BU
LM2575-3.3WU**
–40° to +85°C
5-Pin TO-263
LM2575-5.0BU
LM2575-5.0WU**
–40° to +85°C
5-Pin TO-263
LM2575-12BU
LM2575-12WU**
–40° to +85°C
5-Pin TO-263
Notes:
*
Adjustable output regulators.
**
RoHS compliant with "high-melting solder" exemption.
†
Contact factory for bent or staggered leads option.
May 2009
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M9999-051209-B
Micrel, Inc.
LM2575
Pin Configuration
5-Pin TO-220 (T)
ON/OFF
FB
GND
OUT
VIN
5-Pin TO-263 (U)
PWR GND
1
24 NC
NC
2
23 NC
NC
3
22 NC
NC
4
21 NC
NC 1
16 VIN
NC
5
20 NC
NC 2
15 NC
NC
6
19 NC
OUT 3
14 GND
FB
7
18 OUT
NC 4
13 GND
SIG GND
8
17 OUT
GND 5
12 GND
NC
9
16 NC
NC 6
11 GND
ON/OFF 10
15 VIN
FB 7
10 NC
NC 11
14 VIN
NC 8
9 ON/OFF
PWR GND 12
13 NC
16-Pin Plastic DIP (N)
May 2009
5
4
3
2
1
TAB
TAB
5 ON/OFF
4 FB
3 GND
2 OUT
1 VIN
24-Pin Wide SOIC (WM)
3
M9999-051209-B
Micrel, Inc.
LM2575
Absolute Maximum Ratings(1)
Operating Ratings
Maximum Supply Voltage (VIN) ......................................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 (Ts) .........................–65°C to +150°C
Minimum ESD Rating
C = 100pF, R = 1.5kΩ.............................................. 2kV
FB Pin ...................................................................... 1kV
Supply Voltage (VIN).......................................................40V
Junction Temperature Range (TJ).......–40°C ≤ TJ ≤ +125°C
Electrical Characteristics
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 = 200mA.
Symbol
Parameter
Condition
SYSTEM PARAMETERS, ADJUSTABLE REGULATORS (Note 3) Test Circuit Figure 1
Feedback Voltage
VOUT
Feedback Voltage LM2575
VIN = 12V , ILOAD = 0.2A
VOUT = 5V
1.230
0.2A ≤ ILOAD ≤ 1A, 8V ≤ VIN ≤ 40V
VOUT = 5V
1.230
η
Efficiency
VIN = 12V, ILOAD = 1A, VOUT = 5V
SYSTEM PARAMETERS, 3.3V REGULATORS (Note 3) Test Circuit Figure 1
Output Voltage
VOUT
Output Voltage LM2575-3.3
VOUT
Output Voltage LM2575-5.0
VOUT
η
May 2009
Output Voltage LM2575-12
Efficiency
1.193/1.180
1.267/1.280
82
3.3
0.2A ≤ ILOAD ≤ 1A, 8V ≤ VIN ≤ 40V
VOUT = 3.3V
3.3
3.234
3.366
3.168/3.135
3.432/3.465
75
VIN = 12V , ILOAD = 0.2A
VOUT = 5V
5.0
0.2A ≤ ILOAD ≤ 1A, 8V ≤ VIN ≤ 40V
VOUT = 5V
5.0
η
Efficiency
VIN = 12V, ILOAD = 1A
SYSTEM PARAMETERS, 12V REGULATORS (Note 3) Test Circuit Figure 1
Output Voltage
1.217
1.243
VIN = 12V , ILOAD = 0.2A
VOUT = 3.3V
η
Efficiency
VIN = 12V, ILOAD = 1A
SYSTEM PARAMETERS, 5V REGULATORS (Note 3) Test Circuit Figure 1
Output Voltage
Typ
4.900
5.100
4.800/4.750
5.200/5.250
82
VIN = 25V , ILOAD = 0.2A
VOUT = 12V
12
0.2A ≤ ILOAD ≤ 1A, 15V ≤ VIN ≤ 40V
VOUT = 12V
12
VIN = 25V, ILOAD = 1A
88
4
LM2575
Limit
(Note 2)
11.760
12.240
11.520/11.400
12.480/12.600
Units
(Limits)
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)
%
M9999-051209-B
Micrel, Inc.
LM2575
Typ
LM2575
Limit
(Note 2)
Units
(Limits)
IB
Feedback Bias Current
VOUT = 5V
DEVICE PARAMETERS, FIXED and ADJUSTABLE REGULATORS
50
100/500
nA
fO
Oscillator Frequency
52
VSAT
Saturation Voltage
IOUT = 1A (Note 4)
0.9
DC
Max Duty Cycle (ON)
(Note 5)
98
ICL
Current Limit
Peak Current, tON ≤ 3µs (Note 4)
2.2
IL
Output Leakage Current
VIN = 40V, (Note 6),
IQ
Quiescent Current
(Note 6)
(Note 6)
ISTBY
Standby Quiescent Current
ON/OFF Pin = 5V (OFF)
Symbol
Parameter
Condition
DEVICE PARAMETERS, ADJUSTABLE REGULATOR
47/42
58/63
1.2/1.4
93
Output = 0V
Output = –1V
Output = –1V
75
30
5
10
50
200
T Package, Junction to Ambient (Note 7)
θJA
Thermal Resistance
T Package, Junction to Ambient (Note 8)
θJA
θJC
T Package, Junction to Case
N Package, Junction to Ambient (Note 9)
θJA
WM Package, Junction to Ambient (Note 9)
θJA
ON/OFF CONTROL, FIXED and ADJUSTABLE REGULATORS Test Circuit Figure 1
VIH
VIL
ON/OFF Pin Logic
Input Level
VOUT = 0V
VOUT = 5V
IIH
ON/OFF Pin Logic
Current
ON /OFF Pin = 5V (OFF)
IIL
1.7/1.3
3.0/3.2
2
65
45
2
85
100
1.4
1.2
2.2/2.4
1.0/0.8
4
30
ON /OFF Pin = 0V (ON)
0.01
10
kHz
kHz(min)
kHz(max)
V
V(max)
%
%(max)
A
A(min)
A(max)
mA(max)
mA
mA(max)
mA
mA(max)
µA
µA(max)
°C/W
V(min)
V(max)
µA
µA(max)
µA
µA(max)
Notes:
1. Absolute Maximum Rating indicate limits beyond which damage to the device may occur. Operating Ratings indicate conditions for which the device
is intended to be functional, but do not guarantee specific performance limits. For guaranteed specifications and test conditions, see the Electrical
Characteristics.
2. All limits guaranteed at room temperature (standard type face) and at temperature extremes (bold type face). All room temperature limits are100%
production tested. All limits at temperature extreme 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
LM2575/LM1575 is used as shown in Figure 1 test circuit, system performance will be shown in system parameters section of Electrical
Characteristics.
4. Output (pin 2) sourcing current. No diode, inductor or capacitor connected to output.
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 (no external heat sink) for the 5-pin TO-220 package mounted vertically, with 1/2" leads in a socket, or on PC
board with minimum copper area.
8. Junction to ambient thermal resistance (no external heat sink) for the 5-pin TO-220 package mounted vertically, with 1/4" leads soldered to PC
board containing approximately 4 square inches of copper area surrounding the leads.
9. Junction to ambient thermal resistance with approximately 1 square inch of pc board copper surrounding the leads. Additional copper will lower
thermal resistance further.
May 2009
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M9999-051209-B
Micrel, Inc.
LM2575
Test Circuits and Layout Guidelines
FEEDBACK
+VIN
LM2575
1
7V - 40V
U N R E G U L A TE D +
DC INPUT
100µF
4
G ND
3 ON/OFF
OU TPU T
5
VOUT
5.00V
L1
330µH
2
+
D1
MBR360
C IN
R2
C OUT
470µF
R1
L
O
A
D
C IN — 100µF, 75V Aluminum Electrolytic
C OUT — 470µF, 15V Aluminum Electrolytic
D1 — Schottky, MBR360
L1 — 330µH, 415-0926 (AIE)
R1 — 1k, 0.01%
R2 — 3.065k, 0.01%
5-pin TO-220 socket—2936 (Loranger Mfg. Co.)
4-pin TO-3 socket—8112-AG7 (Augat Inc.)
FEEDBACK
+VIN
1
7V - 40V
U N R E G U L A TE D +
DC INPUT
100µF
LM2575-5.0
G ND
3 ON/OFF
C IN
5
4
OU TPU T
2
VOUT
5.00V
L1
330µH
+
D1
MBR360
C OUT
220µF
L
O
A
D
C IN — 100µF, 75V Aluminum Electrolytic
C OUT — 330µF, 15V Aluminum Electrolytic
D1 — Schottky, MBR360
L1 — 330µH, 415-0926 (AIE)
5-pin TO-220 socket — 2936 (Loranger Mfg. Co.)
4-pin TO-3 socket — 8112-AG7 (Augat Inc.)
Not e: Pin numbers are for TO-220 Package
Figure 1.
As in any switching regulator, layout is very important.
Rapidly switching currents associated with wiring
inductance generate voltage transient switch can cause
problems. For minimal stray inductance and ground
May 2009
loops, the length of the leads indicated by heavy lines
should be kept as short as possible. Single-point
grounding (as indicated) or ground plane construction
should be used for best results.
6
M9999-051209-B
Micrel, Inc.
LM2575
Supply Current
vs. Duty Cycle
20
20.0
Measured at
Ground Pin
TJ
VOUT = 5V
18
16
S U P P LY C U R R E N T ( m A )
SUP PLY CURRE NT (mA )
Supply Current
14
12
10
I LO AD to 1A
8
17.5
15.0
12.5
10.0
5.0
6
2.0
4
0
0
10
20
30
40
50
60
I L O AD= 200 mA
7.5
VIN from 7V to 40V
0
20
INPUT VOLTAGE ( V)
1
100
0
-75 -50 -25 0 25 50 75 100125 150
150
VIN= 12V
50
0
-75 -50 -25 0 25 50 75 100 125150
100
95
1.0
-55 C
-40 C
0.8
25 C
0.6 125 C
150 C
0.4
0
3.5
3.0
2.5
2.0
1.5
1.0
0.5
0
-75 -50 -25 0
VO U T = 1.23V
IL OAD= 200 mA
85
25 50 75 100125150
0.2
0.4
0.6
0.8
75
1A
VOUT = 3V
0
-2
-4
10
15
20
25
0
5
10 15 20 25 30 35 40
INPUT VOLTAGE ( V)
2
5
200 mA
200 mA
80
60
1.0
Line Regulation
0
1A
65
14
12 Normalized toVIN = 10V
VOUT = 5V
10
I
= 500mA
8 LO AD
TJ = 25
6
4
-6
VOUT = 12V
90
70
30
S TA N D B Y Q U I E S C E N T C U R R E N T ( µ A )
4.0
N O R M ALI ZED FEED BAC K VO LTAG E ( m V)
INPUT VOLTAGE ( V)
5.0
4.5
VON/OFF= 5V
100
SW I TC H C U R R EN T ( A)
Minimum Operating
Voltage
VIN = 40V
Efficiency
1.2
EFFI CI ENCY ( % )
2
80
200
Switch
Saturation Voltage
SATU R ATI O N VO LTAG E ( V)
O U TPU T C U R R EN T ( A)
VIN = 25V
60
Standby
Quiescent Current
D U TY C YC L E ( % )
Current Limit
3
40
S TA N D B Y Q U I E S C E N T C U R R E N T ( µ A )
Typical Characteristics (circuit of Figure 1)
Feedback Pin Current
100
75
50
25
0
-25
-50
-75
-100
-75 -50 -25 0
25 50 75 100 125150
May 2009
Normalized
Output Voltage
75
50
VIN = 12V
I LO AD = 200mA
Normalized toTJ = 25 C
25
0
-25
-50
-75
-100
-75 -50 -25 0
25 50 75 100125150
Oscillator Frequency
+8
+6
Normalized at 25C
+4
+2
0
-2
VIN = 40V
-4
--6
VIN = 12V
-8
-75 -50 -25 0 25 50 75 100125150
7
Dropout Voltage
INPUT- OUTPUT DIFFERENTIAL ( V)
100
NO RM ALI ZED FREQ UENCY ( % )
O UTPUT VO LTAG E CHANG E ( m V)
INPUT VOL TAGE ( V)
2.0
1.5
I LO AD= 1A
VOUT = 5%
RIND = 0.2
1.0
0.5
I LO AD = 200 mA
0
-75 -50 -25 0 25 50 75 100125150
M9999-051209-B
Micrel, Inc.
LM2575
Normalized
Feedback Voltage*
25
20
15
10
5
FE E D B A C K V O LTA G E C H A N G E ( m V )
N O R M ALI ZED FEED BAC K VO LTAG E ( m V)
Typical Characteristics (continued)
VIN = 12V
IL O AD= 200mA
Normalized toTJ = 25 C
0
-5
-10
-15
-20
-25
-75 -50 -25 0
25 50 75 100125150
Feedback Voltage
vs Duty Cycle*
20
I LO AD = 200 mA
15
10
5
VIN = 40V
0
-5
VIN = 7V
-10
-15
-20
0
20
40
60
80
100
D U TY C YC LE ( % )
* Adjustable version only
May 2009
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M9999-051209-B
Micrel, Inc.
LM2575
Functional Characteristics (circuit of Figure 1)
Load Transient Response
Output
Voltage
Change
Switching Waveforms
+100mV
A
10V
0
0
–100mV
B
1A
0
1A
C
1.0A
Output
Current
.5A
0.5A
0
D
0
100µs/div.
V OUT = 5V VIN = 20V
V OUT = 5V
A: Output pin voltage 10V/div
B: Output pin current 1A/div
C: Inductor current 0.5A/div
D: Output ripple voltage 20 mV/div. AC coupled
Horizontal Time Base: 5µs/div
Functional Diagrams
V IN
1
FB
4
INTERNAL
REGULATOR
5
ON/OFF
2
OUT
3
GND
5
ON/OFF
2
OUT
3
GND
FIXED GAIN
ERROR AMP
3.1k
+
-
-
1.23V
BAND-GAP
REFERENCE
1 AMP
SWITCH
COMPARATOR
+
1.0k
ON/OFF
52 kHz
OSCILLATOR
DRIVER
RESET
THERMAL
SHUTDOWN
CURRENT
LIMIT
Note: Pin numbers are for the TO-220 package
Fixed Regulator
VIN
INTERNAL
REGULATOR
1
ON/OFF
FIXED GAIN
ERROR AMP
FB
4
-
1.23V
BAND-GAP
REFERENCE
1 AMP
SWITCH
COMPARATOR
+
+
-
52 kHz
OSCILLATOR
DRIVER
RESET
THERMAL
SHUTDOWN
CURRENT
LIMIT
Adjustable Regulator
May 2009
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M9999-051209-B
Micrel, Inc.
LM2575
Package Information
0.780
MAX
(19.812)
PIN 1
0.030-0.110
RAD
(0.762-2.794)
.250±0.005
(6.350±0.127)
0.025±0.015
(0.635±0.381)
0.290-0.320
(7.336-8.128)
0.020
(0.508)
0.040
TYP
(1.016)
0.130±0.005
(3.302±0.127)
0-10
0.020 MIN
(0.508)
0.009-0.015
(0.229-0.381)
0.018±0.003
(0.457±0.076)
0.100±0.010
(2.540±0.254)
0.125 MIN
(3.175)
+0.025
–0.015
+0.635
8.255
–0.381
0.325
(
)
16-Pin Plastic DIP (N)
24-Pin Wide SOIC (WM)
May 2009
10
M9999-051209-B
Micrel, Inc.
LM2575
5-Pin TO-220 (T)
5-Pin TO-263 (T)
May 2009
11
M9999-051209-B
Micrel, Inc.
LM2575
MICREL, INC. 2180 FORTUNE DRIVE SAN JOSE, CA 95131 USA
TEL +1 (408) 944-0800 FAX +1 (408) 474-1000 WEB http://www.micrel.com
The 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.
© 2000 Micrel, Incorporated.
May 2009
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M9999-051209-B