LM2575

52kHz Simple 1A Buck Regulator

General Description Features

The LM2575 series of monolithic integrated circuits • 3.3V, 5V, 12V, and adjustable output versions
provide all the active functions for a step-down (buck) • Voltage over specified line and load conditions:
switching regulator. Fixed versions are available with a – Fixed version: ±3% max. output voltage
3.3V, 5V, 12V, fixed output. Adjustable versions have an
– Adjustable version: ±2% max. feedback voltage
• Guaranteed 1A output current
output voltage range from 1.23V to 37V. Both versions are

• Wide input voltage range

capable of driving a 1A load with excellent line and load
regulation.
– 4V to 40V
• Wide output voltage range
These regulators are simple to use because they require a
minimum number of external components and include
internal frequency compensation and a fixed-frequency – 1.23V to 37V
oscillator. • Requires only 4 external components
The LM2575 series offers a high efficiency replacement for • 52kHz fixed frequency internal oscillator
popular three-terminal adjustable linear regulators. It • Low power standby mode IQ typically <200µA
• 80% efficiency (adjustable version typically >80%)
substantially reduces the size of the heat sink, and in

• Uses readily available standard inductors

many cases no heat sink is required.

• Thermal shutdown and current limit protection

A standard series of inductors available from several

• 100% electrical thermal limit burn-in

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 Applications
•
adjustable versions, and the output voltage is guaranteed
Simple high-efficiency step-down (buck) regulator
•
to ±3% for fixed versions, within specified input voltages
Efficient pre-regulator for linear regulators
•
and output load conditions. The oscillator frequency is
guaranteed to ±10%. External shutdown is included, On-card switching regulators
featuring less than 200µA standby current. The output • Positive to negative converter (inverting Buck-Boost)
•
switch includes cycle-by-cycle current limiting and thermal
Isolated flyback converter using minimum number of
shutdown for full protection under fault conditions.
external components
Data sheets and support documentation can be found on • Negative boost converter
Micrel’s web site at www.micrel.com.
___________________________________________________________________________________________________________

Typical Applications
7V–40V 7V–40V
Unregulated +5V, 1A Unregulated +5V, 1A
4 Feedback 4 Feedback
DC Input 1 Regulated DC Input 1 Regulated
LM2575-5.0 Output L1 Output LM2575 Output L1 Output
+VIN +VIN
2 330µH + 2 330µH + R2 3.09k
+ 3 5 + 3 5
CIN Gnd On/Off CIN Gnd On/Off
D1 COUT D1 COUT
100µF 100µF R1 1k
1N5822 330µF 1N5822 330µF

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

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Ordering Information
Part Number
Pb-Free /
Standard 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.

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Pin Configuration

5 ON/OFF 5 ON/OFF
4 FB 4 FB

TAB
TAB

3 GND 3 GND
2 OUT 2 OUT
1 VIN 1 VIN

5-Pin TO-220 (T) 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) 24-Pin Wide SOIC (WM)

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Absolute Maximum Ratings(1) Operating Ratings

Maximum Supply Voltage (VIN) ......................................45V Supply Voltage (VIN).......................................................40V
ON/OFF Pin Input Voltage. ......................–0.3V ≤ V ≤ +40V Junction Temperature Range (TJ).......–40°C ≤ TJ ≤ +125°C
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

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.
LM2575
Limit Units
Symbol Parameter Condition Typ (Note 2) (Limits)
SYSTEM PARAMETERS, ADJUSTABLE REGULATORS (Note 3) Test Circuit Figure 1
Feedback Voltage VIN = 12V , ILOAD = 0.2A 1.230 V
VOUT = 5V 1.217 V(min)
1.243 V(max)
VOUT
Feedback Voltage LM2575 0.2A ≤ ILOAD ≤ 1A, 8V ≤ VIN ≤ 40V 1.230 V
VOUT = 5V 1.193/1.180 V(min)
1.267/1.280 V(max)
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 3.3 V
VOUT = 3.3V 3.234 V(min)
3.366 V(max)
VOUT
Output Voltage LM2575-3.3 0.2A ≤ ILOAD ≤ 1A, 8V ≤ VIN ≤ 40V 3.3 V
VOUT = 3.3V 3.168/3.135 V(min)
3.432/3.465 V(max)
Efficiency VIN = 12V, ILOAD = 1A 75 %
SYSTEM PARAMETERS, 5V REGULATORS (Note 3) Test Circuit Figure 1
Output Voltage VIN = 12V , ILOAD = 0.2A 5.0 V
VOUT = 5V 4.900 V(min)
5.100 V(max)
VOUT
Output Voltage LM2575-5.0 0.2A ≤ ILOAD ≤ 1A, 8V ≤ VIN ≤ 40V 5.0 V
VOUT = 5V 4.800/4.750 V(min)
5.200/5.250 V(max)
Efficiency VIN = 12V, ILOAD = 1A 82 %
SYSTEM PARAMETERS, 12V REGULATORS (Note 3) Test Circuit Figure 1
Output Voltage VIN = 25V , ILOAD = 0.2A 12 V
VOUT = 12V 11.760 V(min)
12.240 V(max)
VOUT
Output Voltage LM2575-12 0.2A ≤ ILOAD ≤ 1A, 15V ≤ VIN ≤ 40V 12 V
VOUT = 12V 11.520/11.400 V(min)
12.480/12.600 V(max)
Efficiency VIN = 25V, ILOAD = 1A 88 %

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LM2575
Limit Units
Symbol Parameter Condition Typ (Note 2) (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 kHz
47/42 kHz(min)
58/63 kHz(max)
VSAT Saturation Voltage IOUT = 1A (Note 4) 0.9 V
1.2/1.4 V(max)
DC Max Duty Cycle (ON) (Note 5) 98 %
93 %(max)
ICL Current Limit Peak Current, tON ≤ 3µs (Note 4) 2.2 A
1.7/1.3 A(min)
3.0/3.2 A(max)
IL Output Leakage Current VIN = 40V, (Note 6), Output = 0V 2 mA(max)
Output = –1V 75 mA
(Note 6) Output = –1V 30 mA(max)
IQ Quiescent Current (Note 6) 5 mA
10 mA(max)
ISTBY Standby Quiescent Current ON/OFF Pin = 5V (OFF) 50 µA
200 µA(max)
JA Thermal Resistance T Package, Junction to Ambient (Note 7) 65 °C/W
JA T Package, Junction to Ambient (Note 8) 45
JC T Package, Junction to Case 2
JA N Package, Junction to Ambient (Note 9) 85
JA WM Package, Junction to Ambient (Note 9) 100
ON/OFF CONTROL, FIXED and ADJUSTABLE REGULATORS Test Circuit Figure 1
VIH ON/OFF Pin Logic VOUT = 0V 1.4 2.2/2.4 V(min)
VIL Input Level VOUT = 5V 1.2 1.0/0.8 V(max)
IIH ON/OFF Pin Logic ON /OFF Pin = 5V (OFF) 4 µA
Current 30 µA(max)
IIL ON /OFF Pin = 0V (ON) 0.01 µA
10 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.

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Test Circuits and Layout Guidelines

FEEDBACK
+VIN 4
LM2575 L1
VOUT
5.00V
C IN — 100µF, 75V Aluminum Electrolytic
1 OU TPU T C OUT — 470µF, 15V Aluminum Electrolytic
D1 — Schottky, MBR360
7V - 40V 100µF 2 330µH + L1 — 330µH, 415-0926 (AIE)
U N R E G U L A TE D + G ND 3 ON/OFF 5 C OUT R2 L
R1 — 1k, 0.01%
DC INPUT D1 470µF O
C IN A R2 — 3.065k, 0.01%
MBR360 5-pin TO-220 socket—2936 (Loranger Mfg. Co.)
R1 D
4-pin TO-3 socket—8112-AG7 (Augat Inc.)

FEEDBACK
+VIN 4
LM2575-5.0 L1
VOUT
5.00V
C IN — 100µF, 75V Aluminum Electrolytic
1 OU TPU T C OUT — 330µF, 15V Aluminum Electrolytic
D1 — Schottky, MBR360
7V - 40V 100µF 2 330µH + L1 — 330µH, 415-0926 (AIE)
U N R E G U L A TE D + G ND 3 ON/OFF 5 C OUT L
5-pin TO-220 socket — 2936 (Loranger Mfg. Co.)
DC INPUT D1 220µF O
C IN A 4-pin TO-3 socket — 8112-AG7 (Augat Inc.)
MBR360
D

Not e: Pin numbers are for TO-220 Package

Figure 1.

As in any switching regulator, layout is very important. loops, the length of the leads indicated by heavy lines
Rapidly switching currents associated with wiring should be kept as short as possible. Single-point
inductance generate voltage transient switch can cause grounding (as indicated) or ground plane construction
problems. For minimal stray inductance and ground should be used for best results.

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Typical Characteristics (circuit of Figure 1)

Supply Current Standby

S TA N D B Y Q U I E S C E N T C U R R E N T ( µ A )
Supply Current vs. Duty Cycle Quiescent Current
20 20.0 200
Measured at VIN = 40V
SUP PLY CURRE NT (mA )

S U P P LY C U R R E N T ( m A )
18 Ground Pin 17.5
TJ
16 VOUT = 5V 15.0 150
14 12.5
VON/OFF= 5V
12 10.0 100
10 7.5 I L O AD= 200 mA
VIN= 12V
8 I LO AD to 1A 5.0 50
6 2.0 VIN from 7V to 40V

4 0 0
0 10 20 30 40 50 60 0 20 40 60 80 100 -75 -50 -25 0 25 50 75 100 125150
INPUT VOLTAGE ( V) D U TY C YC L E ( % )

Switch
Current Limit Saturation Voltage Efficiency
3 1.2 100
SATU R ATI O N VO LTAG E ( V)

VIN = 25V
O U TPU T C U R R EN T ( A)

95 VOUT = 12V
1A

EFFI CI ENCY ( % )
1.0 90
2 -55 C
85 200 mA 200 mA
-40 C
0.8 80
25 C
75 1A
1
0.6 125 C 70 VOUT = 3V
150 C
65
0 0.4 60
-75 -50 -25 0 25 50 75 100125 150 0 0.2 0.4 0.6 0.8 1.0 0 5 10 15 20 25 30 35 40
SW I TC H C U R R EN T ( A) INPUT VOLTAGE ( V)

Minimum Operating
Line Regulation Feedback Pin Current
N O R M ALI ZED FEED BAC K VO LTAG E ( m V)

Voltage
S TA N D B Y Q U I E S C E N T C U R R E N T ( µ A )

5.0 14 100
4.5 12 Normalized toVIN = 10V 75
VOUT = 5V
4.0 10
INPUT VOLTAGE ( V)

I LO AD = 500mA 50
3.5 8
TJ = 25
3.0 6 25
2.5 4 0
2.0 2 -25
1.5 0
VO U T = 1.23V -50
1.0 -2
IL OAD= 200 mA -75
0.5 -4
0 -6 -100
-75 -50 -25 0 25 50 75 100125150 0 5 10 15 20 25 30 -75 -50 -25 0 25 50 75 100 125150
INPUT VOL TAGE ( V)

Normalized
Output Voltage Oscillator Frequency Dropout Voltage
INPUT- OUTPUT DIFFERENTIAL ( V)
O UTPUT VO LTAG E CHANG E ( m V)

100 +8 2.0
NO RM ALI ZED FREQ UENCY ( % )

VIN = 12V Normalized at 25C VOUT = 5%

75 I LO AD = 200mA +6 RIND = 0.2
I LO AD= 1A
Normalized toTJ = 25 C +4 1.5
50
25 +2
0 0 1.0
-25 -2
VIN = 40V I LO AD = 200 mA
-50 -4 0.5
-75 --6
VIN = 12V
-100 -8 0
-75 -50 -25 0 25 50 75 100125150 -75 -50 -25 0 25 50 75 100125150 -75 -50 -25 0 25 50 75 100125150

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Typical Characteristics (continued)

Normalized Feedback Voltage

N O R M ALI ZED FEED BAC K VO LTAG E ( m V)

FE E D B A C K V O LTA G E C H A N G E ( m V )
Feedback Voltage* vs Duty Cycle*
25 20
VIN = 12V I LO AD = 200 mA
20 15
IL O AD= 200mA
15
Normalized toTJ = 25 C 10
10
5 5 VIN = 40V
0 0
-5 -5
-10 VIN = 7V
-10
-15
-20 -15
-25 -20
-75 -50 -25 0 25 50 75 100125150 0 20 40 60 80 100
D U TY C YC LE ( % )

* Adjustable version only

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Functional Characteristics (circuit of Figure 1)

Load Transient Response Switching Waveforms

+100mV A 10V
Output
Voltage 0 0
Change
–100mV B 1A
0
1A
C
1.0A .5A
Output
Current 0.5A 0
D
0
100µs/div.

V OUT = 5V V OUT = 5V VIN = 20V

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 INTERNAL
1 REGULATOR ON/OFF 5 ON/OFF

FB 4
FIXED GAIN
3.1k ERROR AMP
1 AMP
+ COMPARATOR SWITCH
1.0k +
-
- DRIVER

2 OUT

1.23V
BAND-GAP 52 kHz THERMAL CURRENT
REFERENCE OSCILLATOR RESET SHUTDOWN LIMIT
3 GND

Note: Pin numbers are for the TO-220 package

Fixed Regulator

VIN INTERNAL
1 REGULATOR
ON/OFF 5 ON/OFF

FIXED GAIN
ERROR AMP
1 AMP
FB 4 + COMPARATOR SWITCH

+
-
- DRIVER
2 OUT

1.23V
BAND-GAP 52 kHz THERMAL CURRENT
RESET
REFERENCE OSCILLATOR SHUTDOWN LIMIT 3 GND

Adjustable Regulator

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Package Information

0.780
MAX
(19.812)
PIN 1

0.030-0.110
RAD
.250±0.005 (0.762-2.794)
(6.350±0.127)

0.025±0.015
(0.635±0.381) 0.290-0.320
0.020
0.040 (0.508) (7.336-8.128)
0.130±0.005 TYP
(3.302±0.127) (1.016)

0-10

0.020 MIN 0.009-0.015

(0.508) (0.229-0.381)
0.125 MIN
(3.175) +0.025
0.018±0.003 0.100±0.010 0.325
–0.015
(0.457±0.076) (2.540±0.254) +0.635
(8.255
–0.381 )
16-Pin Plastic DIP (N)

24-Pin Wide SOIC (WM)

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5-Pin TO-220 (T)

5-Pin TO-263 (T)

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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.

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