1.0 & 3.0 AMP MINICONVERTER
SWITCHING REGULATORS LM2575
LM2576
© 1998 SEMTECH CORP. 652 MITCHELL ROAD NEWBURY PARK CA 91320
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 -0.3VVIN 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
© 1998 SEMTECH CORP. 652 MITCHELL ROAD NEWBURY PARK CA 91320
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
© 1998 SEMTECH CORP. 652 MITCHELL ROAD NEWBURY PARK CA 91320
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
© 1998 SEMTECH CORP. 652 MITCHELL ROAD NEWBURY PARK CA 91320
April 7, 1998
4
LM2575 - OPERATIONAL DATA
1.0 & 3.0 AMP MINICONVERTER
SWITCHING REGULATORS LM2575
LM2576
© 1998 SEMTECH CORP. 652 MITCHELL ROAD NEWBURY PARK CA 91320
April 7, 1998
5
LM2575 - OPERATIONAL DATA
1.0 & 3.0 AMP MINICONVERTER
SWITCHING REGULATORS LM2575
LM2576
© 1998 SEMTECH CORP. 652 MITCHELL ROAD NEWBURY PARK CA 91320
April 7, 1998
6
LM2575 - OPERATIONAL DATA
1.0 & 3.0 AMP MINICONVERTER
SWITCHING REGULATORS LM2575
LM2576
© 1998 SEMTECH CORP. 652 MITCHELL ROAD NEWBURY PARK CA 91320
April 7, 1998
7
LM2576 - OPERATIONAL DATA
1.0 & 3.0 AMP MINICONVERTER
SWITCHING REGULATORS LM2575
LM2576
© 1998 SEMTECH CORP. 652 MITCHELL ROAD NEWBURY PARK CA 91320
April 7, 1998
8
LM2576 - OPERATIONAL DATA
1.0 & 3.0 AMP MINICONVERTER
SWITCHING REGULATORS LM2575
LM2576
© 1998 SEMTECH CORP. 652 MITCHELL ROAD NEWBURY PARK CA 91320
April 7, 1998
9
LM2576 - OPERATIONAL DATA
1.0 & 3.0 AMP MINICONVERTER
SWITCHING REGULATORS LM2575
LM2576
© 1998 SEMTECH CORP. 652 MITCHELL ROAD NEWBURY PARK CA 91320
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
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
© 1998 SEMTECH CORP. 652 MITCHELL ROAD NEWBURY PARK CA 91320
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 0.03 for the
LM2576 or 0.07 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
© 1998 SEMTECH CORP. 652 MITCHELL ROAD NEWBURY PARK CA 91320
April 7, 1998
12
TYPICAL BUCK SHUTDOWN
TURN-ON DELAY
1.0 & 3.0 AMP MINICONVERTER
SWITCHING REGULATORS LM2575
LM2576
© 1998 SEMTECH CORP. 652 MITCHELL ROAD NEWBURY PARK CA 91320
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
© 1998 SEMTECH CORP. 652 MITCHELL ROAD NEWBURY PARK CA 91320
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
V
12
5.3
I
IN
O
OUT
+
)2575LM(
V
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
O
INO
O
DV
V
V02.0V
V
V
1I
VV V
P+
+
+
1.0 & 3.0 AMP MINICONVERTER
SWITCHING REGULATORS LM2575
LM2576
© 1998 SEMTECH CORP. 652 MITCHELL ROAD NEWBURY PARK CA 91320
April 7, 1998
15
INVERTING BUCK/BOOST SHUTDOWN
1.0 & 3.0 AMP MINICONVERTER
SWITCHING REGULATORS LM2575
LM2576
© 1998 SEMTECH CORP. 652 MITCHELL ROAD NEWBURY PARK CA 91320
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
© 1998 SEMTECH CORP. 652 MITCHELL ROAD NEWBURY PARK CA 91320
April 7, 1998
17
OUTLINE - TO-220 (T-XX-V Option)
OUTLINE - TO-220 (T-XX-H Option)
OUTLINE - TO-220 (T-XX Option)