LM2576S-12T - Semtech Corp.

1.0 & 3.0 AMP MINICONVERTER

SWITCHING REGULATORS LM2575

LM2576

April 7, 1998

1

FEATURES

• Pin for pin interchangeable with National’s

LM2575/LM2576 series

• DC-to-DC buck or buck/boost converter requiring

only 4 support components

• Fixed or adjustable voltages

• Preset output voltages of 3.3, 5 and 12V

• Wide output voltage range, 1.23 to 35V

• 82% typical efficiency @ 5V

• Wide input voltage range, 4V to 40V

• Inhibit/enable control pin

DESCRIPTION

The LM2575/6 series switching regulators are mono-

lithic integrated circuits designed for use in “buck” or

“buck/boost” regulator applications requiring accurate

output voltages over combined variations of line, load

and temperature. This unique series greatly simplifies

switching power supply design. The LM2575 has a

maximum output current of 1A and the LM2576 is

rated for 3A.

The LM2575/6 series miniconverters include a

switching regulator and compensation network all

within the same package. Just add a choke, catch

diode and two capacitors to obtain an efficient DC-to-

DC converter. Current limit and thermal shutdown

features of the LM2575/6 series fully protect the device

against overstress conditions.

The LM2575/6 series offers an alternative to popular 3

terminal linear regulators by providing higher efficiency

with reduced heatsink size. In many applications a heat

sink will not be required.

TEL:805-498-2111 FAX:805-498-3804 WEB:http://www.semtech.com

ABSOLUTE MAXIMUM RATINGS

Parameter Symbol Maximum Units

Input Voltage VIN 45 V

On/Off Pin Input

Voltage -0.3≤V≤VIN V

Output Voltage to

Common (Steady

State) -1 V

Power Dissipation PDInternally

Limited W

Thermal Resistance

Junction to Case

TO-220

TO-263 θJC 2.0

2.0 °C/W

Thermal Resistance

Junction to Ambient

TO-220

TO-263 θJA 55

60 °C/W

Operating Junction

Temperature Range TJ-40 to 125 °C

Storage Temperature

Range TSTG -40 to 125 °C

Lead Temperature

(Soldering) 10 Sec TLEAD 260 °C

ESD Class 2

ORDERING INFORMATION

Notes:

(1) XX = Voltage Option 3.3, 5.0, 12, and ADJ (1.23V

to 35V).

(2) T-XX = Straight in-line; T-XX-V = Vertical Stag-

gered; T-XX-H = Horizontal Staggered.

(3) Add suffix ‘TR’ for tape and reel (TO-263).

DEVICE(1) PACKAGE CURRENT

LM2575T-XX TO-220(2) 1A

LM2575S-XX TO-263(3)

LM2576T-XX TO-220(2) 3A

LM2576S-XX TO-263(3)

BLOCK DIAGRAM

1.0 & 3.0 AMP MINICONVERTER

SWITCHING REGULATORS LM2575

LM2576

April 7, 1998

2

ELECTRICAL CHARACTERISTICS

Unless otherwise specified, VIN = 12V for 3.3V, 5V and ADJ options; 25V for 12V; VOUT = 5V for ADJ, TJ = 25ºC.

VIN rated = 40V; IO = 0.5 to 3A (LM2576), 0.2 to 1A (LM2575).

(CONTINUED NEXT PAGE)

Test Conditions Test Limits

Parameter Symbol VIN IOTJ(4) Min Typ Max Units

Output Voltage VO0.5A 3.23 3.30 3.37 V

LM2576-3.3 8V to O.T. 3.14 3.30 3.47

VIN Rated 3.20 3.30 3.40

LM2576-5 VO0.5A 4.90 5.00 5.10 V

8V to O.T. 4.76 5.00 5.25

VIN Rated 4.85 5.00 5.15

LM2576-12 VO0.5A 11.76 12.00 12.24 V

15V to O.T. 11.40 12.00 12.60

VIN Rated 11.52 12.00 12.48

Feedback Voltage IFB 0.5A 1.217 1.230 1.243 V

VOUT = 5V 8V to O.T. 1.180 1.230 1.280

LM2576-ADJ VIN Rated 1.193 1.230 1.267

Feedback Bias Current IB12V 0.5A 50 100 nA

LM2576-ADJ O.T. 500

Output Voltage VO0.2A 3.23 3.30 3.37 V

LM2575-3.3 8V to O.T. 3.14 3.30 3.47

VIN Rated 3.20 3.30 3.40

LM2575-5 VO0.2A 4.90 5.00 5.10 V

8V to O.T. 4.75 5.00 5.25

VIN Rated 4.85 5.00 5.15

LM2575-12 VO0.2A 11.76 12.00 12.24 V

15V to O.T. 11.40 12.00 12.60

VIN Rated 11.52 12.00 12.48

Feedback Voltage IFB 0.2A 1.217 1.230 1.243 V

VOUT = 5V 8V to O.T. 1.180 1.230 1.280

LM2575-ADJ VIN Rated 1.193 1.230 1.267

Feedback Bias Current

LM2575-ADJ IB12V 0.2A O.T. 500 nA

1.0 & 3.0 AMP MINICONVERTER

SWITCHING REGULATORS LM2575

LM2576

April 7, 1998

3

NOTES:

(1) Output sourcing current-resistive load, no inductor or capacitor.

(2) Feedback = VO + 1.0V.

(3) Feedback = 0V.

(4) Over Temp. (O.T.) = over specified operating junction temperature range.

ELECTRICAL CHARACTERISTICS (cont.)

Test Conditions Test Limits

Parameter Symbol VIN IOTJ(4) Min Typ Max Units

Efficiency/Option

3.3 η12V LM2575-1A 77 %

5 LM2576-3A 82

12 15V 88

ADJ VO = 5V 12V 82

Switching Frequency FSX 47 52 58 kHz

O.T. 43 52 62

Saturation Voltage (1) VSAT LM2575-1A O.T. 0.9 1.2 V

LM2576-3A O.T. 0.9 1.4

Max Duty Cycle (On) (3) DC 93 98 %

Current Limit(1) ICL 4.2 5.8 6.9 A

Peak Current LM2576 O.T. 3.5 7.5

Peak Current LM2575 ICL 1.7 2.2 3.0 A

O.T. 1.3 3.2

Output Leakage Current(2)

Output = 0V ILVIN RATED 2 mA

Output = -1V 7.5 30

Quiescent Current(2) IQ510mA

O.T. 12

Standby Quiescent ISTBY 50 µA

Current (On/Off Pin = 5V) O.T. 50 500

On/Off Pin Logic

Input Level VIH 2.2 1.4 V

VOUT = 0V O.T. 2.4 1.4

VOUT = Option VIL 1.2 1.0 V

O.T. 1.2 0.8

On/Off Input Current

On/Off = 5V (Off) IIH 0.5A 12 30 µA

On/Off = 0V (On) IIL 0.5A 0 10

1.0 & 3.0 AMP MINICONVERTER

SWITCHING REGULATORS LM2575

LM2576

April 7, 1998

4

LM2575 - OPERATIONAL DATA

1.0 & 3.0 AMP MINICONVERTER

SWITCHING REGULATORS LM2575

LM2576

April 7, 1998

5

LM2575 - OPERATIONAL DATA

1.0 & 3.0 AMP MINICONVERTER

SWITCHING REGULATORS LM2575

LM2576

April 7, 1998

6

LM2575 - OPERATIONAL DATA

1.0 & 3.0 AMP MINICONVERTER

SWITCHING REGULATORS LM2575

LM2576

April 7, 1998

7

LM2576 - OPERATIONAL DATA

1.0 & 3.0 AMP MINICONVERTER

SWITCHING REGULATORS LM2575

LM2576

April 7, 1998

8

LM2576 - OPERATIONAL DATA

1.0 & 3.0 AMP MINICONVERTER

SWITCHING REGULATORS LM2575

LM2576

April 7, 1998

9

LM2576 - OPERATIONAL DATA

1.0 & 3.0 AMP MINICONVERTER

SWITCHING REGULATORS LM2575

LM2576

April 7, 1998

10

TYPICAL APPLICATION - BUCK MODE

The above component selections will be adequate for

most applications for output currents from 250mA to

3.0A (LM2576) or 150mA to 1.0A (LM2575). Applica-

tions with VOUT below 5V or above 24V may require

component adjustment for maximum performance;

please contact factory for application assistance.

1. DEVICE SELECTION. Select an appropriate device

from the “Ordering Information” guide based upon volt-

age option and package.

2. THERMAL CONDITIONS. Most applications will not

require a heatsink for the TO-220 package. Approxi-

mate power dissipation is:

3. CATCH DIODE. If the output must be capable of a

sustained short, the IF rating must be above 3A for the

LM2575 and 7A for the LM2576. The use of an ultra

fast diode with soft recovery characteristics or a Schot-

tky will be adequate. The major impact on Schottky

versus an ultra fast is efficiency. Schottkys will provide

approximately 4% to 5% improvement for VOUTS below

12V, whereas above 12V the difference will become

less significant. Breakdown rating must be in excess of

VIN for margin.

4. INPUT CAPACITOR. The value shown will be ade-

quate for most applications. Ripple voltage at the

switching frequency is caused by the input capacitor

supplying load current during the on time of the power

switch. The use of a low ESR switching type capacitor

will minimize ripple to an acceptable level.

IN

O

IN

SATOO V

V

V02.0

VVIV

P+=

LM2575 LM2576

L1330µH 100µH

D13A 7A

CIN 68µF 120µF

COUT 330µF 1,000µF

LM2575 LM2576

L1330µH 100µH

D13A 7A

CIN 68µF 120µF

COUT 330µF 1,000µF

1.0 & 3.0 AMP MINICONVERTER

SWITCHING REGULATORS LM2575

LM2576

April 7, 1998

11

5. LAYOUT. Use short connections with a central point

ground to prevent improper operation caused by stray

inductance and ground loops.

6. OUTPUT CAPACITOR. Ripple voltage on VOUT is

directly related to the value of COUT and the internal re-

sistance ESR of COUT. Output noise can be lowered by

increasing COUT or by selecting a capacitor with a lower

ESR. ESR must be approximately 0.03Ω for the

LM2576 or 0.07Ω for the LM2575, or above to maintain

stability, otherwise raise value of COUT.

7. SWITCHING SPIKES. Switching spikes will also oc-

cur due to distributive capacitance across turns of the

inductor when combined with output capacitor series

inductance (ESL). Reduction to a level at or below the

switching ripple can be achieved by using a post filter

as shown.

SWITCHING SPIKE REDUCTION

1.0 & 3.0 AMP MINICONVERTER

SWITCHING REGULATORS LM2575

LM2576

April 7, 1998

12

TYPICAL BUCK SHUTDOWN

TURN-ON DELAY

1.0 & 3.0 AMP MINICONVERTER

SWITCHING REGULATORS LM2575

LM2576

April 7, 1998

13

UNDER VOLTAGE LOCKOUT

TURN-ON DELAY W I TH SPIKE FILTER

1.0 & 3.0 AMP MINICONVERTER

SWITCHING REGULATORS LM2575

LM2576

April 7, 1998

14

Component stress requirement is very similar to the

buck with a few exceptions:

• catch diode breakdown VBR must be greater than

VIN + |VOUT|

• input capacitor is larger due to the increased peak

current during switch turn on. Power dissipation is

approximately:

Please contact factory for additional assistance when

using the buck/boost topology.

TYPICAL APPLICATION - INVERTING BUCK/BOOST

Inverting buck/boost operation is a different topology of

operation than buck. This difference reduces the out-

put current capability of the device, in that the inductor

must supply all of the load current during the time the

power switch is off. Maximum output current is approxi-

mately:

)2576LM(

V

12

5.3

I

IN

O

OUT























+

≈

)2575LM(

V

12

3.1

I

IN

O

OUT























+

≈

LM2575 LM2576

CIN 47µF 100µF

D13A 7A

L1100µH 68µH

COUT 2,700µF 6,800µF

IOUT 250mA 500mA

LM2575 LM2576

CIN 47µF 100µF

D13A 7A

L1100µH 68µH

COUT 470µF 2,700µF

IOUT 100mA 750mA

IN

O

INSAT

IN

O

INO

O

DV

V

V02.0V

V

1I

VV V

P+











+











+

≈

1.0 & 3.0 AMP MINICONVERTER

SWITCHING REGULATORS LM2575

LM2576

April 7, 1998

15

INVERTING BUCK/BOOST SHUTDOWN

1.0 & 3.0 AMP MINICONVERTER

SWITCHING REGULATORS LM2575

LM2576

April 7, 1998

16

SUPPORT COMPONENTS INFORMATION

PRE-WOUND INDUCTORS:

Hurricane Electronics Lab

P.O. Box 1280

Hurricane Industrial Park

Hurricane, UT 84737

(801) 635-2003

CORE SOURCE:

Micro Metals, Inc.

1190 N. Hawk Circle

Anaheim, CA 92807

(714) 630-7420

CAPACITORS:

VPR Series

Mallory Capacitor Co.

4760 Kentucky Avenue

Indianapolis, IN 46241

(317) 856-3731

511D & 673 Series

Sprague Electric Co.

North Adams, MA

(413) 664-4411

HFQ, HFZ Series

Panasonic Industrial Co.

2 Panasonic Way

Secaucus, NJ 07094

(201) 392-6142

PF, PL Series

Nichicon Corp.

927 E. State Pkwy.

Schaumburg, IL 60195

(708) 843-7600

LXF Series

United Chemi-con

9801 West Higgins Road

Rosemont, IL 60018

(708) 696-2000

HEAT SINKS:

AAVID Engineering Co.

P.O.Box 400

One Kool Path

Laconia, NH 03247

(603) 528-3400

Thermalloy, Inc.

2021 W. Valley View Lane

Dallas, TX 76381

(214) 243-4321

DIODES - CATCH:

Ultra Fast/Soft Recovery

Semtech Corporation

652 Mitchell Road

Newbury Park, CA 91320

(805) 498-2111

DIODES - SCHOTTKY:

Fuji/Collmer Semiconductor

14368 Proton Road

Dallas, TX 76244

(800) 527-0521

Micro Quality

1000 N. Shiloh

Garland, TX 76046

(214) 272-7811

1.0 & 3.0 AMP MINICONVERTER

SWITCHING REGULATORS LM2575

LM2576

April 7, 1998

17

OUTLINE - TO-220 (T-XX-V Option)

OUTLINE - TO-220 (T-XX-H Option)

OUTLINE - TO-220 (T-XX Option)

1.0 & 3.0 AMP MINICONVERTER

SWITCHING REGULATORS LM2575

LM2576

April 7, 1998

18

OUTLINE - TO-263

LM2575,

LM2576

PIN FUNCTION

1V

IN

2OUTPUT

3 COMMON

4 FEEDBACK

5ON/OFF

TAB IS COMMON

PIN CONFIGURATIONS

TO-220 TO-263