LM2575
52kHz Simple 1A Buck Regulator
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
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 LM2575-5.0
+
CIN
100µF
+VIN
1
3
Gnd
5
On/Off
2
Output
4Feedback
L1
330µH +
D1
1N5822
COUT
330µF
+5V, 1A
Regulated
Output
Note: Pin numbers are for TO-220 Package R2
R1
7V–40V
Unregulated
DC Input LM2575
+
CIN
100µF
+VIN
1
3
Gnd
5
On/Off
2
Output
4Feedback
L1
330µH +
D1
1N5822
COUT
330µF
R2 3.09k
R1 1k
VOUT = 1.23 1 +
()
+5V, 1A
Regulated
Output
Note: Pin numbers are for TO-220 Package
Fixed Regulation in Typical Application Adjustable Regulation in Fixed Output Application
Micrel, Inc. LM2575
May 2009 2 M9999-051209-B
Ordering Information
Part Number
Standard Pb-Free /
RoHS Compliant 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.
Micrel, Inc. LM2575
May 2009 3 M9999-051209-B
Pin Configur ation
TAB
3 GND
4FB
5 ON/OF
F
2 OUT
1 VIN
TAB
5 ON/OF
F
4FB
3 GND
2 OUT
1 VIN
5-Pin TO-220 (T) 5-Pin TO-263 (U)
1NC
NC
OUT
NC
GND
NC
FB
NC
16 VIN
NC
GND
GND
GND
GND
NC
ON/OFF
15
14
13
12
11
10
9
2
3
4
5
6
7
8 PWR GND NC1312
NC VIN1411
1PWR GND
NC
NC
NC
NC
NC
FB
SIG GND
NC
ON/OFF
24 NC
NC
NC
NC
NC
NC
OUT
OUT
NC
VIN
23
22
21
20
19
18
17
16
15
2
3
4
5
6
7
8
9
10
16-Pin Plastic DIP (N) 24-Pin Wide SOIC (WM)
Micrel, Inc. LM2575
May 2009 4 M9999-051209-B
Absolute Maximum Ratings(1)
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 = 1.5k.............................................. 2kV
FB Pin ...................................................................... 1kV
Operating Ratings
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 Typ
LM2575
Limit
(Note 2) Units
(Limits)
SYSTEM PARAMETERS, ADJUSTABLE REGULATORS (Note 3) Test Circuit Figure 1
Feedback Voltage VIN = 12V , ILOAD = 0.2A
VOUT = 5V
1.230
1.217
1.243
V
V(min)
V(max)
VOUT Feedback Voltage LM2575 0.2A ILOAD 1A, 8V VIN 40V
VOUT = 5V
1.230
1.193/1.180
1.267/1.280
V
V(min)
V(max)
η Efficiency VIN = 12V, ILOAD = 1A, VOUT = 5V 82 %
SYSTEM PARAMETERS, 3.3V REGULATORS (Note 3) Test Circuit Figure 1
Output Voltage VIN = 12V , ILOAD = 0.2A
VOUT = 3.3V
3.3
3.234
3.366
V
V(min)
V(max)
VOUT Output Voltage LM2575-3.3 0.2A ILOAD 1A, 8V VIN 40V
VOUT = 3.3V
3.3
3.168/3.135
3.432/3.465
V
V(min)
V(max)
η Efficiency VIN = 12V, ILOAD = 1A 75 %
SYSTEM PARAMETERS, 5V REGULATORS (Note 3) Test Circuit Figure 1
Output Voltage VIN = 12V , ILOAD = 0.2A
VOUT = 5V
5.0
4.900
5.100
V
V(min)
V(max)
VOUT Output Voltage LM2575-5.0 0.2A ILOAD 1A, 8V VIN 40V
VOUT = 5V
5.0
4.800/4.750
5.200/5.250
V
V(min)
V(max)
η Efficiency VIN = 12V, ILOAD = 1A 82 %
SYSTEM PARAMETERS, 12V REGULATORS (Note 3) Test Circuit Figure 1
Output Voltage VIN = 25V , ILOAD = 0.2A
VOUT = 12V
12
11.760
12.240
V
V(min)
V(max)
VOUT Output Voltage LM2575-12 0.2A ILOAD 1A, 15V VIN 40V
VOUT = 12V
12
11.520/11.400
12.480/12.600
V
V(min)
V(max)
η Efficiency VIN = 25V, ILOAD = 1A 88 %
Micrel, Inc. LM2575
May 2009 5 M9999-051209-B
Symbol Parameter Condition Typ
LM2575
Limit
(Note 2) Units
(Limits)
DEVICE PARAMETERS, ADJUSTABLE REGULATOR
IB Feedback Bias Current VOUT = 5V 50 100/500 nA
DEVICE PARAMETERS, FIXED and ADJUSTABLE REGULATORS
fO Oscillator Frequency 52
47/42
58/63
kHz
kHz(min)
kHz(max)
VSAT Saturation Voltage IOUT = 1A (Note 4) 0.9
1.2/1.4
V
V(max)
DC Max Duty Cycle (ON) (Note 5) 98
93
%
%(max)
ICL Current Limit Peak Current, tON 3µs (Note 4) 2.2
1.7/1.3
3.0/3.2
A
A(min)
A(max)
IL Output Leakage Current VIN = 40V, (Note 6), Output = 0V
Output = –1V
(Note 6) Output = –1V
75
2
30
mA(max)
mA
mA(max)
IQ Quiescent Current (Note 6) 5
10
mA
mA(max)
ISTBY Standby Quiescent Current ON/OFF Pin = 5V (OFF) 50
200
µA
µA(max)
θJA T Package, Junction to Ambient (Note 7) 65
θJA T Package, Junction to Ambient (Note 8) 45
θJC T Package, Junction to Case 2
θJA N Package, Junction to Ambient (Note 9) 85
θJA
Thermal Resistance
WM Package, Junction to Ambient (Note 9) 100
°C/W
ON/OFF CONTROL, FIXED and ADJUSTABLE REGULATORS Test Circuit Figure 1
VIH
VIL
ON/OFF Pin Logic
Input Level
VOUT = 0V
VOUT = 5V
1.4
1.2
2.2/2.4
1.0/0.8
V(min)
V(max)
IIH ON /OFF Pin = 5V (OFF) 4
30
µA
µA(max)
IIL
ON/OFF Pin Logic
Current
ON /OFF Pin = 0V (ON) 0.01
10
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.
Micrel, Inc. LM2575
May 2009 6 M9999-051209-B
Test Circuits and Layout Guidelines
LM2575
+100µF
+VIN
1
3GND 5ON/OFF 2
OUTPUT
4
FEEDBACK
L1
330µH +
D1
MBR360
COUT
470µF
R2
R1
VOUT
5.00V
7V - 40V
UNREGULATED
DC INPUT CIN
L
O
A
D
CIN
— 100µF, 75V Aluminum Electrolytic
COUT
— 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.)
LM2575-5.0
+100µF
+VIN
1
3GND 5ON/OFF 2
OUTPUT
4
FEEDBACK
L1
330µH +
D1
MBR360
COUT
220µF
VOUT
5.00V
Note: Pin numbers are for TO-220 Package
7V - 40V
UNREGULATED
DC INPUT CIN
CIN 100µF, 75V Aluminum Electrolytic
COUT— 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.)
L
O
A
D
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
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.
Micrel, Inc. LM2575
May 2009 7 M9999-051209-B
Typical Characteristics (circuit of Figure 1 )
Supply Curre nt
INPUT VOLTAGE (V)
SUPPLY CURRENT (mA)
20 Measured at
Ground Pin
TJ
V
OUT
= 5V
18
16
14
12
10
8
6
40 102030405060
ILOAD
to 1A
Supply Curre nt
vs. Duty Cycle
DUTY CYCLE (%)
20.0
17.5
15.0
12.5
10.0
7.5
5.0
2.0
0020406080100
VIN from 7V to 40V
ILOAD
= 200 mA
SUPPLY CURRENT (mA)
200
150
100
50
0
-75
VIN
= 12V
STANDBY QUIESCENT CURRENT (µA)
Standb
y
Quiescent Current
VIN
= 40V
-50 -25 0 25 50 75 100 125150
Curre nt Limi t
3
2
1
0
-75
VIN = 25V
OUTPUT CURRENT (A)
INPUT VOLTAGE (V)
100
EFFICIENCY (%)
Efficiency
VOUT
= 12V
-50 -25 0 25 50 75 100125 150
95
90
85
80
75
70
65
60
200 mA
200 mA
VOUT
= 3V
1A
0 5 10 15 20 25 30 35 40
Minimum Operating
Voltage
5.0
ILOAD
= 200 mA
INPUT VOLTAGE (V)
Line R e gulati on
INPUT VOLTAGE (V)
14
0
NORMALIZED FEEDBACK VOLTAGE (mV)
100
-100
-75
STANDBY QUIESCENT CURRENTA)
Feedback Pin Current
-50 -25 0 25 50 75 100 125150
VOUT
= 1.23V
4.5
4.0
3.5
3.0
2.5
2.0
1.5
1.0
0.5
0
-75 -50 -25 0 25 50 75 100125150
12
10
8
6
4
2
0
-2
-4
-6
5 1015202530
75
50
25
0
-25
-50
-75
+8
-8
-75
NORMALIZED FREQUENCY (%)
Oscillator Frequency
-50 -25 0 25 50 75 100125150
+6
+4
+2
0
-2
-4
--6 VIN = 12V
VIN = 40V
Normalized at 25C
Normalized toVIN
= 10V
VOUT = 5V
ILOAD = 500mA
TJ = 25
V
ON/OFF
= 5V
Switch
Satura tio n Volta ge
SWITCH CURRENT (A)
1.2
-55 C
1.0
0.8
0.6
0.4
0
SATURATION VOLTAGE (V)
0.20.40.60.81.0
25 C
125 C
150 C
-40 C
Dropout Vol ta ge
INPUT-OUTPUT DIFFERENTIAL (V)
2.0
-75 -50 -25 0 25 50 75 100125150
V
OUT = 5%
RIND = 0.2
ILOAD
= 1A
ILOAD
= 200 mA
1.5
1.0
0.5
0
Normalized
Output Voltage
OUTPUT VOLTAGE CHANGE (mV
)
100
75
50
25
0
-25
-50
-75
-100
-75 -50 -25 0 25 50 75 100125150
VIN = 12V
ILOAD = 200mA
Normalized toT
J = 25 C
1A
Micrel, Inc. LM2575
May 2009 8 M9999-051209-B
Typical Characteristics (continued)
Normalize
d
Feedback Voltage*
NORMALIZED FEEDBACK VOLTAGE (mV)
25
20
15
10
5
0
-5
-10
-15
-20
-25
-75 -50 -25 0 25 50 75 100125150
VIN
= 12V
ILOAD
= 200mA
Normalized toT
J= 25 C
Feedback Voltag
e
vs Duty Cycle*
DUTY CYCLE (%)
FEEDBACK VOLTAGE CHANGE (mV)
20
15
10
5
0
-5
-10
-15
-20
ILOAD = 200 mA
VIN = 40V
VIN = 7V
020406080100
* Adjustable version only
Micrel, Inc. LM2575
May 2009 9 M9999-051209-B
Functional Characteristics (circuit of Figure 1)
Load Transient Response
100µs/div.
+100mV
0
–100mV
Output
Voltage
Change
1.0A
0.5A
0
Output
Current
VOUT = 5V
Switching Waveforms
10V
0
1A
0
1A
.5A
0
A
B
C
D
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
VOUT = 5V VIN = 20V
Functional Diagrams
ON/OFF
COMPARATOR
FIXED GAIN
ERROR AMP
1 AMP
SWITCH
OUT
DRIVER
+
-
+
-
VIN
FB
1.23V
BAND-GAP
REFERENCE
52 kHz
OSCILLATOR RESET THERMAL
SHUTDOWN
CURRENT
LIMIT
5
2
3
1
Note: Pin numbers are for the TO-220 package
INTERNAL
REGULATOR ON/OFF
GND
3.1k
1.0k
4
Fixed Regulator
ON/OFF
COMPARATOR
FIXED GAIN
ERROR AMP
1 AMP
SWITCH
OUT
DRIVER
+
-
+
-
V
IN
FB
1.23V
BAND-GAP
REFERENCE
52 kHz
OSCILLATOR RESET THERMAL
SHUTDOWN
CURRENT
LIMIT
5
2
3
1
4
INTERNAL
REGULATOR ON/OFF
GND
Adjustable Regulator
Micrel, Inc. LM2575
May 2009 10 M9999-051209-B
Package Information
0.020
(0.508)
0.018±0.003
(0.457±0.076)
PIN 1
0.780
(19.812)
.250±0.005
(6.350±0.127)
0.025±0.015
(0.635±0.381)
0.100±0.010
(2.540±0.254)
MAX
0.030-0.110
(0.762-2.794) RAD
0.125
(3.175) MIN
0.020
(0.508) MIN
0.130±0.005
(3.302±0.127)
+0.025
–0.015
+0.635
–0.381
0.325
8.255
()
0.009-0.015
(0.229-0.381)
0-10
0.290-0.320
(7.336-8.128)
0.040
(1.016)TYP
16-Pin Plastic DIP (N)
24-Pin Wide SOIC (WM)
Micrel, Inc. LM2575
May 2009 11 M9999-051209-B
5-Pin TO-220 (T)
5-Pin TO-263 (T)
Micrel, Inc. LM2575
May 2009 12 M9999-051209-B
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.