www.DataSheet.co.

kr

LM1575/LM2575/LM2575HV Series SIMPLE SWITCHER 1A Step-Down Voltage Regulator

August 2004

LM1575/LM2575/LM2575HV
SIMPLE SWITCHER ® 1A Step-Down Voltage Regulator
General Description Features
The LM2575 series of regulators are monolithic integrated n 3.3V, 5V, 12V, 15V, and adjustable output versions
circuits that provide all the active functions for a step-down n Adjustable version output voltage range,
(buck) switching regulator, capable of driving a 1A load with 1.23V to 37V (57V for HV version) ± 4% max over
excellent line and load regulation. These devices are avail- line and load conditions
able in fixed output voltages of 3.3V, 5V, 12V, 15V, and an n Guaranteed 1A output current
adjustable output version. n Wide input voltage range, 40V up to 60V for HV version
Requiring a minimum number of external components, these n Requires only 4 external components
regulators are simple to use and include internal frequency n 52 kHz fixed frequency internal oscillator
compensation and a fixed-frequency oscillator. n TTL shutdown capability, low power standby mode
The LM2575 series offers a high-efficiency replacement for n High efficiency
popular three-terminal linear regulators. It substantially re- n Uses readily available standard inductors
duces the size of the heat sink, and in many cases no heat
n Thermal shutdown and current limit protection
sink is required.
n P+ Product Enhancement tested
A standard series of inductors optimized for use with the
LM2575 are available from several different manufacturers.
This feature greatly simplifies the design of switch-mode Applications
power supplies. n Simple high-efficiency step-down (buck) regulator
Other features include a guaranteed ± 4% tolerance on out- n Efficient pre-regulator for linear regulators
put voltage within specified input voltages and output load n On-card switching regulators
conditions, and ± 10% on the oscillator frequency. External n Positive to negative converter (Buck-Boost)
shutdown is included, featuring 50 µA (typical) standby cur-
rent. The output switch includes cycle-by-cycle current limit-
ing, as well as thermal shutdown for full protection under
fault conditions.

Typical Application (Fixed Output Voltage

Versions)

01147501
Note: Pin numbers are for the TO-220 package.

SIMPLE SWITCHER ® is a registered trademark of National Semiconductor Corporation.

© 2004 National Semiconductor Corporation DS011475 www.national.com

Datasheet pdf - http://www.DataSheet4U.net/

www.DataSheet.co.kr

LM1575/LM2575/LM2575HV
Block Diagram and Typical Application

01147502
3.3V, R2 = 1.7k
5V, R2 = 3.1k
12V, R2 = 8.84k
15V, R2 = 11.3k
For ADJ. Version
R1 = Open, R2 = 0Ω
Note: Pin numbers are for the TO-220 package.

FIGURE 1.

Connection Diagrams (XX indicates output voltage option. See Ordering Information table for complete part
number.)
Straight Leads Bent, Staggered Leads
5–Lead TO-220 (T) 5-Lead TO-220 (T)

01147522 01147523 01147524

Top View Top View Side View

LM2575T-XX or LM2575HVT-XX LM2575T-XX Flow LB03 or
See NS Package Number T05A LM2575HVT-XX Flow LB03
See NS Package Number T05D

www.national.com 2

Datasheet pdf - http://www.DataSheet4U.net/

www.DataSheet.co.kr

LM1575/LM2575/LM2575HV
Connection Diagrams (XX indicates output voltage option. See Ordering Information table for complete part
number.) (Continued)

16–Lead DIP (N or J) 24-Lead Surface Mount (M)

01147525
*No Internal Connection
Top View 01147526
LM2575N-XX or LM2575HVN-XX *No Internal Connection
See NS Package Number N16A Top View
LM1575J-XX-QML LM2575M-XX or LM2575HVM-XX
See NS Package Number J16A See NS Package Number M24B

TO-263(S)
5-Lead Surface-Mount Package

01147529
Top View

01147530
Side View
LM2575S-XX or LM2575HVS-XX
See NS Package Number TS5B

Ordering Information
Package NSC Standard High Temperature
Type Package Voltage Rating Voltage Rating Range
Number (40V) (60V)
5-Lead TO-220 T05A LM2575T-3.3 LM2575HVT-3.3
Straight Leads LM2575T-5.0 LM2575HVT-5.0
LM2575T-12 LM2575HVT-12
LM2575T-15 LM2575HVT-15
LM2575T-ADJ LM2575HVT-ADJ
5-Lead TO-220 T05D LM2575T-3.3 Flow LB03 LM2575HVT-3.3 Flow LB03
Bent and LM2575T-5.0 Flow LB03 LM2575HVT-5.0 Flow LB03
Staggered Leads LM2575T-12 Flow LB03 LM2575HVT-12 Flow LB03
LM2575T-15 Flow LB03 LM2575HVT-15 Flow LB03
LM2575T-ADJ Flow LB03 LM2575HVT-ADJ Flow LB03

3 www.national.com

Datasheet pdf - http://www.DataSheet4U.net/

www.DataSheet.co.kr

LM1575/LM2575/LM2575HV
Ordering Information (Continued)
Package NSC Standard High Temperature
Type Package Voltage Rating Voltage Rating Range
Number (40V) (60V)
16-Pin Molded N16A LM2575N-5.0 LM2575HVN-5.0 −40˚C ≤ TJ ≤ +125˚C
DIP LM2575N-12 LM2575HVN-12
LM2575N-15 LM2575HVN-15
LM2575N-ADJ LM2575HVN-ADJ
24-Pin M24B LM2575M-5.0 LM2575HVM-5.0
Surface Mount LM2575M-12 LM2575HVM-12
LM2575M-15 LM2575HVM-15
LM2575M-ADJ LM2575HVM-ADJ
5-Lead TO-263 TS5B LM2575S-3.3 LM2575HVS-3.3
Surface Mount LM2575S-5.0 LM2575HVS-5.0
LM2575S-12 LM2575HVS-12
LM2575S-15 LM2575HVS-15
LM2575S-ADJ LM2575HVS-ADJ
16-Pin Ceramic J16A LM1575J-3.3-QML
DIP LM1575J-5.0-QML
LM1575J-12-QML −55˚C ≤ TJ ≤ +150˚C
LM1575J-15-QML
LM1575J-ADJ-QML

www.national.com 4

Datasheet pdf - http://www.DataSheet4U.net/

www.DataSheet.co.kr

LM1575/LM2575/LM2575HV
Absolute Maximum Ratings (Note 1) Minimum ESD Rating
If Military/Aerospace specified devices are required, (C = 100 pF, R = 1.5 kΩ) 2 kV
please contact the National Semiconductor Sales Office/ Lead Temperature
Distributors for availability and specifications.
(Soldering, 10 sec.) 260˚C
Maximum Supply Voltage
LM1575/LM2575 45V
Operating Ratings
LM2575HV 63V
ON /OFF Pin Input Voltage −0.3V ≤ V ≤ +VIN Temperature Range

Output Voltage to Ground LM1575 −55˚C ≤ TJ ≤ +150˚C

(Steady State) −1V LM2575/LM2575HV −40˚C ≤ TJ ≤ +125˚C

Power Dissipation Internally Limited Supply Voltage

Storage Temperature Range −65˚C to +150˚C LM1575/LM2575 40V

Maximum Junction Temperature 150˚C LM2575HV 60V

LM1575-3.3, LM2575-3.3, LM2575HV-3.3

Electrical Characteristics
Specifications with standard type face are for TJ = 25˚C, and those with boldface type apply over full Operating Tempera-
ture Range .
Symbol Parameter Conditions Typ LM1575-3.3 LM2575-3.3 Units
LM2575HV-3.3 (Limits)
Limit Limit
(Note 2) (Note 3)
SYSTEM PARAMETERS (Note 4) Test Circuit Figure 2
VOUT Output Voltage VIN = 12V, ILOAD = 0.2A 3.3 V
Circuit of Figure 2 3.267 3.234 V(Min)
3.333 3.366 V(Max)
VOUT Output Voltage 4.75V ≤ VIN ≤ 40V, 0.2A ≤ ILOAD ≤ 1A 3.3 V
LM1575/LM2575 Circuit of Figure 2 3.200/3.168 3.168/3.135 V(Min)
3.400/3.432 3.432/3.465 V(Max)
VOUT Output Voltage 4.75V ≤ VIN ≤ 60V, 0.2A ≤ ILOAD ≤ 1A 3.3 V
LM2575HV Circuit of Figure 2 3.200/3.168 3.168/3.135 V(Min)
3.416/3.450 3.450/3.482 V(Max)
η Efficiency VIN = 12V, ILOAD = 1A 75 %

LM1575-5.0, LM2575-5.0, LM2575HV-5.0

Electrical Characteristics
Specifications with standard type face are for TJ = 25˚C, and those with boldface type apply over full Operating Tempera-
ture Range.
Symbol Parameter Conditions Typ LM1575-5.0 LM2575-5.0 Units
LM2575HV-5.0 (Limits)
Limit Limit
(Note 2) (Note 3)
SYSTEM PARAMETERS (Note 4) Test Circuit Figure 2
VOUT Output Voltage VIN = 12V, ILOAD = 0.2A 5.0 V
Circuit of Figure 2 4.950 4.900 V(Min)
5.050 5.100 V(Max)
VOUT Output Voltage 0.2A ≤ ILOAD ≤ 1A, 5.0 V
LM1575/LM2575 8V ≤ VIN ≤ 40V 4.850/4.800 4.800/4.750 V(Min)
Circuit of Figure 2 5.150/5.200 5.200/5.250 V(Max)
VOUT Output Voltage 0.2A ≤ ILOAD ≤ 1A, 5.0 V
LM2575HV 8V ≤ VIN ≤ 60V 4.850/4.800 4.800/4.750 V(Min)
Circuit of Figure 2 5.175/5.225 5.225/5.275 V(Max)

5 www.national.com

Datasheet pdf - http://www.DataSheet4U.net/

www.DataSheet.co.kr

LM1575/LM2575/LM2575HV
LM1575-5.0, LM2575-5.0, LM2575HV-5.0
Electrical Characteristics (Continued)
Specifications with standard type face are for TJ = 25˚C, and those with boldface type apply over full Operating Tempera-
ture Range.
Symbol Parameter Conditions Typ LM1575-5.0 LM2575-5.0 Units
LM2575HV-5.0 (Limits)
Limit Limit
(Note 2) (Note 3)
η Efficiency VIN = 12V, ILOAD = 1A 77 %

LM1575-12, LM2575-12, LM2575HV-12

Electrical Characteristics
Specifications with standard type face are for TJ = 25˚C, and those with boldface type apply over full Operating Tempera-
ture Range .
Symbol Parameter Conditions Typ LM1575-12 LM2575-12 Units
LM2575HV-12 (Limits)
Limit Limit
(Note 2) (Note 3)
SYSTEM PARAMETERS (Note 4) Test Circuit Figure 2
VOUT Output Voltage VIN = 25V, ILOAD = 0.2A 12 V
Circuit of Figure 2 11.88 11.76 V(Min)
12.12 12.24 V(Max)
VOUT Output Voltage 0.2A ≤ ILOAD ≤ 1A, 12 V
LM1575/LM2575 15V ≤ VIN ≤ 40V 11.64/11.52 11.52/11.40 V(Min)
Circuit of Figure 2 12.36/12.48 12.48/12.60 V(Max)
VOUT Output Voltage 0.2A ≤ ILOAD ≤ 1A, 12 V
LM2575HV 15V ≤ VIN ≤ 60V 11.64/11.52 11.52/11.40 V(Min)
Circuit of Figure 2 12.42/12.54 12.54/12.66 V(Max)
η Efficiency VIN = 15V, ILOAD = 1A 88 %

LM1575-15, LM2575-15, LM2575HV-15

Electrical Characteristics
Specifications with standard type face are for TJ = 25˚C, and those with boldface type apply over full Operating Tempera-
ture Range .
Symbol Parameter Conditions Typ LM1575-15 LM2575-15 Units
LM2575HV-15 (Limits)
Limit Limit
(Note 2) (Note 3)
SYSTEM PARAMETERS (Note 4) Test Circuit Figure 2
VOUT Output Voltage VIN = 30V, ILOAD = 0.2A 15 V
Circuit of Figure 2 14.85 14.70 V(Min)
15.15 15.30 V(Max)
VOUT Output Voltage 0.2A ≤ ILOAD ≤ 1A, 15 V
LM1575/LM2575 18V ≤ VIN ≤ 40V 14.55/14.40 14.40/14.25 V(Min)
Circuit of Figure 2 15.45/15.60 15.60/15.75 V(Max)
VOUT Output Voltage 0.2A ≤ ILOAD ≤ 1A, 15 V
LM2575HV 18V ≤ VIN ≤ 60V 14.55/14.40 14.40/14.25 V(Min)
Circuit of Figure 2 15.525/15.675 15.68/15.83 V(Max)
η Efficiency VIN = 18V, ILOAD = 1A 88 %

www.national.com 6

Datasheet pdf - http://www.DataSheet4U.net/

www.DataSheet.co.kr

LM1575/LM2575/LM2575HV
LM1575-ADJ, LM2575-ADJ, LM2575HV-ADJ
Electrical Characteristics
Specifications with standard type face are for TJ= 25˚C, and those with boldface type apply over full Operating Temperature
Range.
Symbol Parameter Conditions Typ LM1575-ADJ LM2575-ADJ Units
LM2575HV-ADJ (Limits)
Limit Limit
(Note 2) (Note 3)
SYSTEM PARAMETERS (Note 4) Test Circuit Figure 2
VOUT Feedback Voltage VIN = 12V, ILOAD = 0.2A 1.230 V
VOUT = 5V 1.217 1.217 V(Min)
Circuit of Figure 2 1.243 1.243 V(Max)
VOUT Feedback Voltage 0.2A ≤ ILOAD ≤ 1A, 1.230 V
LM1575/LM2575 8V ≤ VIN ≤ 40V 1.205/1.193 1.193/1.180 V(Min)
VOUT = 5V, Circuit of Figure 2 1.255/1.267 1.267/1.280 V(Max)
VOUT Feedback Voltage 0.2A ≤ ILOAD ≤ 1A, 1.230 V
LM2575HV 8V ≤ VIN ≤ 60V 1.205/1.193 1.193/1.180 V(Min)
VOUT = 5V, Circuit of Figure 2 1.261/1.273 1.273/1.286 V(Max)
η Efficiency VIN = 12V, ILOAD = 1A, VOUT = 5V 77 %

All Output Voltage Versions

Electrical Characteristics
Specifications with standard type face are for TJ = 25˚C, and those with boldface type apply over full Operating Tempera-
ture Range. Unless otherwise specified, VIN = 12V for the 3.3V, 5V, and Adjustable version, VIN = 25V for the 12V version,
and VIN = 30V for the 15V version. ILOAD = 200 mA.
Symbol Parameter Conditions Typ LM1575-XX LM2575-XX Units
LM2575HV-XX (Limits)
Limit Limit
(Note 2) (Note 3)
DEVICE PARAMETERS
Ib Feedback Bias Current VOUT = 5V (Adjustable Version Only) 50 100/500 100/500 nA
fO Oscillator Frequency (Note 13) 52 kHz
47/43 47/42 kHz(Min)
58/62 58/63 kHz(Max)
VSAT Saturation Voltage IOUT = 1A (Note 5) 0.9 V
1.2/1.4 1.2/1.4 V(Max)
DC Max Duty Cycle (ON) (Note 6) 98 %
93 93 %(Min)
ICL Current Limit Peak Current (Notes 5, 13) 2.2 A
1.7/1.3 1.7/1.3 A(Min)
3.0/3.2 3.0/3.2 A(Max)
IL Output Leakage (Notes 7, 8) Output = 0V 2 2 mA(Max)
Current Output = −1V 7.5 mA
Output = −1V 30 30 mA(Max)
IQ Quiescent Current (Note 7) 5 mA
10/12 10 mA(Max)
ISTBY Standby Quiescent ON /OFF Pin = 5V (OFF) 50 µA
Current 200/500 200 µA(Max)

7 www.national.com

Datasheet pdf - http://www.DataSheet4U.net/

www.DataSheet.co.kr

LM1575/LM2575/LM2575HV
All Output Voltage Versions
Electrical Characteristics (Continued)
Specifications with standard type face are for TJ = 25˚C, and those with boldface type apply over full Operating Tempera-
ture Range. Unless otherwise specified, VIN = 12V for the 3.3V, 5V, and Adjustable version, VIN = 25V for the 12V version,
and VIN = 30V for the 15V version. ILOAD = 200 mA.
Symbol Parameter Conditions Typ LM1575-XX LM2575-XX Units
LM2575HV-XX (Limits)
Limit Limit
(Note 2) (Note 3)
DEVICE PARAMETERS
θJA Thermal Resistance T Package, Junction to Ambient (Note 9) 65
θJA T Package, Junction to Ambient (Note 10) 45 ˚C/W
θJC T Package, Junction to Case 2
θJA N Package, Junction to Ambient (Note 11) 85
θJA M Package, Junction to Ambient (Note 11) 100
θJA S Package, Junction to Ambient (Note 12) 37
ON /OFF CONTROL Test Circuit Figure 2
VIH ON /OFF Pin Logic VOUT = 0V 1.4 2.2/2.4 2.2/2.4 V(Min)
VIL Input Level VOUT = Nominal Output Voltage 1.2 1.0/0.8 1.0/0.8 V(Max)
IIH ON /OFF Pin Input ON /OFF Pin = 5V (OFF) 12 µA
Current 30 30 µA(Max)
IIL ON /OFF Pin = 0V (ON) 0 µA
10 10 µA(Max)

Note 1: Absolute Maximum Ratings 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.
Note 2: All limits guaranteed at room temperature (standard type face) and at temperature extremes (bold type face). All limits are used to calculate Average
Outgoing Quality Level, and all are 100% production tested.
Note 3: All limits guaranteed at room temperature (standard type face) and at temperature extremes (bold type face). All room temperature limits are 100%
production tested. All limits at temperature extremes are guaranteed via correlation using standard Statistical Quality Control (SQC) methods.
Note 4: External components such as the catch diode, inductor, input and output capacitors can affect switching regulator system performance. When the
LM1575/LM2575 is used as shown in the Figure 2 test circuit, system performance will be as shown in system parameters section of Electrical Characteristics.
Note 5: Output (pin 2) sourcing current. No diode, inductor or capacitor connected to output pin.
Note 6: Feedback (pin 4) removed from output and connected to 0V.
Note 7: Feedback (pin 4) removed from output and connected to +12V for the Adjustable, 3.3V, and 5V versions, and +25V for the 12V and 15V versions, to force
the output transistor OFF.
Note 8: VIN = 40V (60V for the high voltage version).
Note 9: Junction to ambient thermal resistance (no external heat sink) for the 5 lead TO-220 package mounted vertically, with 1⁄2 inch leads in a socket, or on a PC
board with minimum copper area.
Note 10: Junction to ambient thermal resistance (no external heat sink) for the 5 lead TO-220 package mounted vertically, with 1⁄2 inch leads soldered to a PC board
containing approximately 4 square inches of copper area surrounding the leads.
Note 11: Junction to ambient thermal resistance with approximately 1 square inch of pc board copper surrounding the leads. Additional copper area will lower
thermal resistance further. See thermal model in Switchers made Simple software.
Note 12: If the TO-263 package is used, the thermal resistance can be reduced by increasing the PC board copper area thermally connected to the package: Using
0.5 square inches of copper area, θJA is 50˚C/W; with 1 square inch of copper area, θJA is 37˚C/W; and with 1.6 or more square inches of copper area, θJA is 32˚C/W.
Note 13: The oscillator frequency reduces to approximately 18 kHz in the event of an output short or an overload which causes the regulated output voltage to drop
approximately 40% from the nominal output voltage. This self protection feature lowers the average power dissipation of the IC by lowering the minimum duty cycle
from 5% down to approximately 2%.
Note 14: Refer to RETS LM1575J for current revision of military RETS/SMD.

www.national.com 8

Datasheet pdf - http://www.DataSheet4U.net/

www.DataSheet.co.kr

LM1575/LM2575/LM2575HV
Typical Performance Characteristics (Circuit of Figure 2)

Normalized Output Voltage Line Regulation

01147532 01147533

Dropout Voltage Current Limit

01147534 01147535

Standby
Quiescent Current Quiescent Current

01147536 01147537

9 www.national.com

Datasheet pdf - http://www.DataSheet4U.net/

www.DataSheet.co.kr

LM1575/LM2575/LM2575HV
Typical Performance Characteristics (Circuit of Figure 2) (Continued)

Switch Saturation
Oscillator Frequency Voltage

01147538 01147539

Efficiency Minimum Operating Voltage

01147540 01147541

Quiescent Current Feedback Voltage

vs Duty Cycle vs Duty Cycle

01147542 01147543

www.national.com 10

Datasheet pdf - http://www.DataSheet4U.net/

www.DataSheet.co.kr

LM1575/LM2575/LM2575HV
Typical Performance Characteristics (Circuit of Figure 2) (Continued)

Maximum Power Dissipation

Feedback Pin Current (TO-263) (See (Note 12))

01147528
01147505

Switching Waveforms Load Transient Response

01147506
VOUT = 5V 01147507

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: 5 µs/div

Test Circuit and Layout Guidelines Single-point grounding (as indicated) or ground plane con-
struction should be used for best results. When using the
As in any switching regulator, layout is very important. Rap- Adjustable version, physically locate the programming resis-
idly switching currents associated with wiring inductance tors near the regulator, to keep the sensitive feedback wiring
generate voltage transients which can cause problems. For short.
minimal inductance and ground loops, the length of the leads
indicated by heavy lines should be kept as short as possible.

11 www.national.com

Datasheet pdf - http://www.DataSheet4U.net/

www.DataSheet.co.kr

LM1575/LM2575/LM2575HV
Test Circuit and Layout Guidelines (Continued)

Fixed Output Voltage Versions

01147508
CIN — 100 µF, 75V, Aluminum Electrolytic
COUT — 330 µF, 25V, Aluminum Electrolytic
D1 — Schottky, 11DQ06
L1 — 330 µH, PE-52627 (for 5V in, 3.3V out, use 100 µH, PE-92108)

Adjustable Output Voltage Version

01147509

where VREF = 1.23V, R1 between 1k and 5k.

R1 — 2k, 0.1%
R2 — 6.12k, 0.1%
Note: Pin numbers are for the TO-220 package.

FIGURE 2.

www.national.com 12

Datasheet pdf - http://www.DataSheet4U.net/

www.DataSheet.co.kr

LM1575/LM2575/LM2575HV
LM2575 Series Buck Regulator Design Procedure
PROCEDURE (Fixed Output Voltage Versions) EXAMPLE (Fixed Output Voltage Versions)
Given: VOUT = Regulated Output Voltage (3.3V, 5V, 12V, or Given: VOUT = 5V VIN(Max) = 20V ILOAD(Max) = 0.8A
15V) VIN(Max) = Maximum Input Voltage ILOAD(Max) =
Maximum Load Current
1. Inductor Selection (L1) A. Select the correct Inductor 1. Inductor Selection (L1) A. Use the selection guide
value selection guide from Figures 3, 4, 5, 6 (Output shown in Figure 4. B. From the selection guide, the
voltages of 3.3V, 5V, 12V or 15V respectively). For other inductance area intersected by the 20V line and 0.8A line is
output voltages, see the design procedure for the adjustable L330. C. Inductor value required is 330 µH. From the table
version. B. From the inductor value selection guide, identify in Figure 9, choose AIE 415-0926, Pulse Engineering
the inductance region intersected by VIN(Max) and PE-52627, or RL1952.
ILOAD(Max), and note the inductor code for that region. C.
Identify the inductor value from the inductor code, and
select an appropriate inductor from the table shown in
Figure 9. Part numbers are listed for three inductor
manufacturers. The inductor chosen must be rated for
operation at the LM2575 switching frequency (52 kHz) and
for a current rating of 1.15 x ILOAD. For additional inductor
information, see the inductor section in the Application Hints
section of this data sheet.
2. Output Capacitor Selection (COUT) A. The value of the 2. Output Capacitor Selection (COUT) A. COUT = 100 µF
output capacitor together with the inductor defines the to 470 µF standard aluminum electrolytic. B. Capacitor
dominate pole-pair of the switching regulator loop. For voltage rating = 20V.
stable operation and an acceptable output ripple voltage,
(approximately 1% of the output voltage) a value between
100 µF and 470 µF is recommended. B. The capacitor’s
voltage rating should be at least 1.5 times greater than the
output voltage. For a 5V regulator, a rating of at least 8V is
appropriate, and a 10V or 15V rating is recommended.
Higher voltage electrolytic capacitors generally have lower
ESR numbers, and for this reason it may be necessary to
select a capacitor rated for a higher voltage than would
normally be needed.
3. Catch Diode Selection (D1) A. The catch-diode current 3. Catch Diode Selection (D1) A. For this example, a 1A
rating must be at least 1.2 times greater than the maximum current rating is adequate. B. Use a 30V 1N5818 or SR103
load current. Also, if the power supply design must Schottky diode, or any of the suggested fast-recovery
withstand a continuous output short, the diode should have diodes shown in Figure 8.
a current rating equal to the maximum current limit of the
LM2575. The most stressful condition for this diode is an
overload or shorted output condition. B. The reverse voltage
rating of the diode should be at least 1.25 times the
maximum input voltage.
4. Input Capacitor (CIN) An aluminum or tantalum 4. Input Capacitor (CIN) A 47 µF, 25V aluminum electrolytic
electrolytic bypass capacitor located close to the regulator is capacitor located near the input and ground pins provides
needed for stable operation. sufficient bypassing.

13 www.national.com

Datasheet pdf - http://www.DataSheet4U.net/

www.DataSheet.co.kr

LM1575/LM2575/LM2575HV
Inductor Value Selection Guides (For Continuous Mode Operation)

01147512
01147510

FIGURE 3. LM2575(HV)-3.3 FIGURE 5. LM2575(HV)-12

01147513
01147511

FIGURE 4. LM2575(HV)-5.0 FIGURE 6. LM2575(HV)-15

01147514

FIGURE 7. LM2575(HV)-ADJ

www.national.com 14

Datasheet pdf - http://www.DataSheet4U.net/

www.DataSheet.co.kr

LM1575/LM2575/LM2575HV
Inductor Value Selection Guides (For Continuous Mode Operation) (Continued)

PROCEDURE (Adjustable Output Voltage Versions) EXAMPLE (Adjustable Output Voltage Versions)
Given: VOUT = Regulated Output Voltage VIN(Max) = Given: VOUT = 10V VIN(Max) = 25V ILOAD(Max) = 1A F =
Maximum Input Voltage ILOAD(Max) = Maximum Load 52 kHz
Current F = Switching Frequency (Fixed at 52 kHz)
1. Programming Output Voltage (Selecting R1 and R2, as 1.Programming Output Voltage (Selecting R1 and R2)
shown in Figure 2 ) Use the following formula to select the
appropriate resistor values.

R1 can be between 1k and 5k. (For best temperature coef-

ficient and stability with time, use 1% metal film resistors) R2 = 1k (8.13 − 1) = 7.13k, closest 1% value is 7.15k

2. Inductor Selection (L1) A. Calculate the inductor Volt • 2. Inductor Selection (L1) A. Calculate E • T (V • µs)
microsecond constant, E • T (V • µs), from the following
formula:

B. E • T = 115 V • µs C. ILOAD(Max) = 1A D. Inductance

Region = H470 E. Inductor Value = 470 µH Choose from AIE
B. Use the E • T value from the previous formula and match part #430-0634, Pulse Engineering part #PE-53118, or
it with the E • T number on the vertical axis of the Inductor Renco part #RL-1961.
Value Selection Guide shown in Figure 7. C. On the hori-
zontal axis, select the maximum load current. D. Identify the
inductance region intersected by the E • T value and the
maximum load current value, and note the inductor code for
that region. E. Identify the inductor value from the inductor
code, and select an appropriate inductor from the table shown
in Figure 9. Part numbers are listed for three inductor manu-
facturers. The inductor chosen must be rated for operation at
the LM2575 switching frequency (52 kHz) and for a current
rating of 1.15 x ILOAD. For additional inductor information, see
the inductor section in the application hints section of this data
sheet.
3. Output Capacitor Selection (COUT) A. The value of the 3. Output Capacitor Selection (COUT) A.
output capacitor together with the inductor defines the
dominate pole-pair of the switching regulator loop. For
stable operation, the capacitor must satisfy the following However, for acceptable output ripple voltage select COUT ≥
requirement: 220 µF COUT = 220 µF electrolytic capacitor

The above formula yields capacitor values between 10 µF

and 2000 µF that will satisfy the loop requirements for stable
operation. But to achieve an acceptable output ripple voltage,
(approximately 1% of the output voltage) and transient re-
sponse, the output capacitor may need to be several times
larger than the above formula yields. B. The capacitor’s volt-
age rating should be at last 1.5 times greater than the output
voltage. For a 10V regulator, a rating of at least 15V or more
is recommended. Higher voltage electrolytic capacitors gen-
erally have lower ESR numbers, and for this reason it may be
necessary to select a capacitor rate for a higher voltage than
would normally be needed.
4. Catch Diode Selection (D1) A. The catch-diode current 4. Catch Diode Selection (D1) A. For this example, a 3A
rating must be at least 1.2 times greater than the maximum current rating is adequate. B. Use a 40V MBR340 or
load current. Also, if the power supply design must 31DQ04 Schottky diode, or any of the suggested
withstand a continuous output short, the diode should have fast-recovery diodes in Figure 8.
a current rating equal to the maximum current limit of the
LM2575. The most stressful condition for this diode is an
overload or shorted output. See diode selection guide in
Figure 8. B. The reverse voltage rating of the diode should
be at least 1.25 times the maximum input voltage.

15 www.national.com

Datasheet pdf - http://www.DataSheet4U.net/

www.DataSheet.co.kr

LM1575/LM2575/LM2575HV
Inductor Value Selection Guides (For Continuous Mode Operation) (Continued)

PROCEDURE (Adjustable Output Voltage Versions) EXAMPLE (Adjustable Output Voltage Versions)
5. Input Capacitor (CIN) An aluminum or tantalum 5. Input Capacitor (CIN) A 100 µF aluminum electrolytic
electrolytic bypass capacitor located close to the regulator is capacitor located near the input and ground pins provides
needed for stable operation. sufficient bypassing.

To further simplify the buck regulator design procedure, National Semiconductor is making available computer design software to
be used with the Simple Switcher line of switching regulators. Switchers Made Simple (version 3.3) is available on a (31⁄2")
diskette for IBM compatible computers from a National Semiconductor sales office in your area.

www.national.com 16

Datasheet pdf - http://www.DataSheet4U.net/

www.DataSheet.co.kr

LM1575/LM2575/LM2575HV
Inductor Value Selection Guides (For Continuous Mode Operation) (Continued)

VR Schottky Fast Recovery

1A 3A 1A 3A
20V 1N5817 1N5820
MBR120P MBR320
SR102 SR302
30V 1N5818 1N5821
MBR130P MBR330 The following The following
11DQ03 31DQ03 diodes are all diodes are all
SR103 SR303 rated to 100V rated to 100V
40V 1N5819 IN5822
11DF1 31DF1
MBR140P MBR340
MUR110 MURD310
11DQ04 31DQ04
HER102 HER302
SR104 SR304
50V MBR150 MBR350
11DQ05 31DQ05
SR105 SR305
60V MBR160 MBR360
11DQ06 31DQ06
SR106 SR306

FIGURE 8. Diode Selection Guide

Inductor Inductor Schott Pulse Eng. Renco

Code Value (Note 15) (Note 16) (Note 17)
L100 100 µH 67127000 PE-92108 RL2444
L150 150 µH 67127010 PE-53113 RL1954
L220 220 µH 67127020 PE-52626 RL1953
L330 330 µH 67127030 PE-52627 RL1952
L470 470 µH 67127040 PE-53114 RL1951
L680 680 µH 67127050 PE-52629 RL1950
H150 150 µH 67127060 PE-53115 RL2445
H220 220 µH 67127070 PE-53116 RL2446
H330 330 µH 67127080 PE-53117 RL2447
H470 470 µH 67127090 PE-53118 RL1961
H680 680 µH 67127100 PE-53119 RL1960
H1000 1000 µH 67127110 PE-53120 RL1959
H1500 1500 µH 67127120 PE-53121 RL1958
H2200 2200 µH 67127130 PE-53122 RL2448

Note 15: Schott Corp., (612) 475-1173, 1000 Parkers Lake Rd., Wayzata, MN 55391.
Note 16: Pulse Engineering, (619) 674-8100, P.O. Box 12236, San Diego, CA 92112.
Note 17: Renco Electronics Inc., (516) 586-5566, 60 Jeffryn Blvd. East, Deer Park, NY 11729.
FIGURE 9. Inductor Selection by Manufacturer’s Part Number

17 www.national.com

Datasheet pdf - http://www.DataSheet4U.net/

www.DataSheet.co.kr

LM1575/LM2575/LM2575HV
Application Hints pletely contained within the core, it generates more electro-
magnetic interference (EMI). This EMI can cause problems
INPUT CAPACITOR (CIN) in sensitive circuits, or can give incorrect scope readings
because of induced voltages in the scope probe.
To maintain stability, the regulator input pin must be by-
passed with at least a 47 µF electrolytic capacitor. The The inductors listed in the selection chart include ferrite pot
capacitor’s leads must be kept short, and located near the core construction for AIE, powdered iron toroid for Pulse
regulator. Engineering, and ferrite bobbin core for Renco.
If the operating temperature range includes temperatures An inductor should not be operated beyond its maximum
below −25˚C, the input capacitor value may need to be rated current because it may saturate. When an inductor
larger. With most electrolytic capacitors, the capacitance begins to saturate, the inductance decreases rapidly and the
value decreases and the ESR increases with lower tempera- inductor begins to look mainly resistive (the DC resistance of
tures and age. Paralleling a ceramic or solid tantalum ca- the winding). This will cause the switch current to rise very
pacitor will increase the regulator stability at cold tempera- rapidly. Different inductor types have different saturation
tures. For maximum capacitor operating lifetime, the characteristics, and this should be kept in mind when select-
capacitor’s RMS ripple current rating should be greater than ing an inductor.
The inductor manufacturer’s data sheets include current and
energy limits to avoid inductor saturation.

INDUCTOR RIPPLE CURRENT

When the switcher is operating in the continuous mode, the
inductor current waveform ranges from a triangular to a
sawtooth type of waveform (depending on the input voltage).
For a given input voltage and output voltage, the peak-to-
peak amplitude of this inductor current waveform remains
constant. As the load current rises or falls, the entire saw-
tooth current waveform also rises or falls. The average DC
INDUCTOR SELECTION value of this waveform is equal to the DC load current (in the
All switching regulators have two basic modes of operation: buck regulator configuration).
continuous and discontinuous. The difference between the If the load current drops to a low enough level, the bottom of
two types relates to the inductor current, whether it is flowing the sawtooth current waveform will reach zero, and the
continuously, or if it drops to zero for a period of time in the switcher will change to a discontinuous mode of operation.
normal switching cycle. Each mode has distinctively different This is a perfectly acceptable mode of operation. Any buck
operating characteristics, which can affect the regulator per- switching regulator (no matter how large the inductor value
formance and requirements. is) will be forced to run discontinuous if the load current is
The LM2575 (or any of the Simple Switcher family) can be light enough.
used for both continuous and discontinuous modes of opera-
tion. OUTPUT CAPACITOR
The inductor value selection guides in Figure 3 through An output capacitor is required to filter the output voltage and
Figure 7 were designed for buck regulator designs of the is needed for loop stability. The capacitor should be located
continuous inductor current type. When using inductor val- near the LM2575 using short pc board traces. Standard
ues shown in the inductor selection guide, the peak-to-peak aluminum electrolytics are usually adequate, but low ESR
inductor ripple current will be approximately 20% to 30% of types are recommended for low output ripple voltage and
the maximum DC current. With relatively heavy load cur- good stability. The ESR of a capacitor depends on many
rents, the circuit operates in the continuous mode (inductor factors, some which are: the value, the voltage rating, physi-
current always flowing), but under light load conditions, the cal size and the type of construction. In general, low value or
circuit will be forced to the discontinuous mode (inductor low voltage (less than 12V) electrolytic capacitors usually
current falls to zero for a period of time). This discontinuous have higher ESR numbers.
mode of operation is perfectly acceptable. For light loads The amount of output ripple voltage is primarily a function of
(less than approximately 200 mA) it may be desirable to the ESR (Equivalent Series Resistance) of the output ca-
operate the regulator in the discontinuous mode, primarily pacitor and the amplitude of the inductor ripple current
because of the lower inductor values required for the discon- (∆IIND). See the section on inductor ripple current in Applica-
tinuous mode. tion Hints.
The selection guide chooses inductor values suitable for The lower capacitor values (220 µF–680 µF) will allow typi-
continuous mode operation, but if the inductor value chosen cally 50 mV to 150 mV of output ripple voltage, while larger-
is prohibitively high, the designer should investigate the value capacitors will reduce the ripple to approximately 20
possibility of discontinuous operation. The computer design mV to 50 mV.
software Switchers Made Simple will provide all component Output Ripple Voltage = (∆IIND) (ESR of COUT)
values for discontinuous (as well as continuous) mode of To further reduce the output ripple voltage, several standard
operation. electrolytic capacitors may be paralleled, or a higher-grade
Inductors are available in different styles such as pot core, capacitor may be used. Such capacitors are often called
toriod, E-frame, bobbin core, etc., as well as different core “high-frequency,” “low-inductance,” or “low-ESR.” These will
materials, such as ferrites and powdered iron. The least reduce the output ripple to 10 mV or 20 mV. However, when
expensive, the bobbin core type, consists of wire wrapped operating in the continuous mode, reducing the ESR below
on a ferrite rod core. This type of construction makes for an 0.05Ω can cause instability in the regulator.
inexpensive inductor, but since the magnetic flux is not com-

www.national.com 18

Datasheet pdf - http://www.DataSheet4U.net/

www.DataSheet.co.kr

LM1575/LM2575/LM2575HV
Application Hints (Continued) high-level TTL or CMOS signal. The ON /OFF pin can be
safely pulled up to +VIN without a resistor in series with it.
Tantalum capacitors can have a very low ESR, and should The ON /OFF pin should not be left open.
be carefully evaluated if it is the only output capacitor. Be-
cause of their good low temperature characteristics, a tan- GROUNDING
talum can be used in parallel with aluminum electrolytics, To maintain output voltage stability, the power ground con-
with the tantalum making up 10% or 20% of the total capaci- nections must be low-impedance (see Figure 2). For the
tance. TO-3 style package, the case is ground. For the 5-lead
The capacitor’s ripple current rating at 52 kHz should be at TO-220 style package, both the tab and pin 3 are ground and
least 50% higher than the peak-to-peak inductor ripple cur- either connection may be used, as they are both part of the
rent. same copper lead frame.
With the N or M packages, all the pins labeled ground, power
CATCH DIODE ground, or signal ground should be soldered directly to wide
Buck regulators require a diode to provide a return path for printed circuit board copper traces. This assures both low
the inductor current when the switch is off. This diode should inductance connections and good thermal properties.
be located close to the LM2575 using short leads and short
printed circuit traces. HEAT SINK/THERMAL CONSIDERATIONS
Because of their fast switching speed and low forward volt- In many cases, no heat sink is required to keep the LM2575
age drop, Schottky diodes provide the best efficiency, espe- junction temperature within the allowed operating range. For
cially in low output voltage switching regulators (less than each application, to determine whether or not a heat sink will
5V). Fast-Recovery, High-Efficiency, or Ultra-Fast Recovery be required, the following must be identified:
diodes are also suitable, but some types with an abrupt 1. Maximum ambient temperature (in the application).
turn-off characteristic may cause instability and EMI prob-
2. Maximum regulator power dissipation (in application).
lems. A fast-recovery diode with soft recovery characteristics
is a better choice. Standard 60 Hz diodes (e.g., 1N4001 or 3. Maximum allowed junction temperature (150˚C for the
1N5400, etc.) are also not suitable. See Figure 8 for Schot- LM1575 or 125˚C for the LM2575). For a safe, conser-
tky and “soft” fast-recovery diode selection guide. vative design, a temperature approximately 15˚C cooler
than the maximum temperature should be selected.
OUTPUT VOLTAGE RIPPLE AND TRANSIENTS 4. LM2575 package thermal resistances θJA and θJC.
The output voltage of a switching power supply will contain a Total power dissipated by the LM2575 can be estimated as
sawtooth ripple voltage at the switcher frequency, typically follows:
about 1% of the output voltage, and may also contain short PD = (VIN) (IQ) + (VO/VIN) (ILOAD) (VSAT)
voltage spikes at the peaks of the sawtooth waveform.
where IQ (quiescent current) and VSAT can be found in the
The output ripple voltage is due mainly to the inductor saw- Characteristic Curves shown previously, VIN is the applied
tooth ripple current multiplied by the ESR of the output minimum input voltage, VO is the regulated output voltage,
capacitor. (See the inductor selection in the application and ILOAD is the load current. The dynamic losses during
hints.) turn-on and turn-off are negligible if a Schottky type catch
The voltage spikes are present because of the fast switching diode is used.
action of the output switch, and the parasitic inductance of When no heat sink is used, the junction temperature rise can
the output filter capacitor. To minimize these voltage spikes, be determined by the following:
special low inductance capacitors can be used, and their
∆TJ = (PD) (θJA)
lead lengths must be kept short. Wiring inductance, stray
capacitance, as well as the scope probe used to evaluate To arrive at the actual operating junction temperature, add
these transients, all contribute to the amplitude of these the junction temperature rise to the maximum ambient tem-
spikes. perature.
An additional small LC filter (20 µH & 100 µF) can be added TJ = ∆TJ + TA
to the output (as shown in Figure 15) to further reduce the If the actual operating junction temperature is greater than
amount of output ripple and transients. A 10 x reduction in the selected safe operating junction temperature determined
output ripple voltage and transients is possible with this filter. in step 3, then a heat sink is required.
When using a heat sink, the junction temperature rise can be
FEEDBACK CONNECTION determined by the following:
The LM2575 (fixed voltage versions) feedback pin must be ∆TJ = (PD) (θJC + θinterface + θHeat sink)
wired to the output voltage point of the switching power
The operating junction temperature will be:
supply. When using the adjustable version, physically locate
both output voltage programming resistors near the LM2575 TJ = TA + ∆TJ
to avoid picking up unwanted noise. Avoid using resistors As above, if the actual operating junction temperature is
greater than 100 kΩ because of the increased chance of greater than the selected safe operating junction tempera-
noise pickup. ture, then a larger heat sink is required (one that has a lower
thermal resistance).
ON /OFF INPUT When using the LM2575 in the plastic DIP (N) or surface
For normal operation, the ON /OFF pin should be grounded mount (M) packages, several items about the thermal prop-
or driven with a low-level TTL voltage (typically below 1.6V). erties of the packages should be understood. The majority of
To put the regulator into standby mode, drive this pin with a the heat is conducted out of the package through the leads,
with a minor portion through the plastic parts of the package.

19 www.national.com

Datasheet pdf - http://www.DataSheet4U.net/

www.DataSheet.co.kr

LM1575/LM2575/LM2575HV
Application Hints (Continued) the available output current. Also, the start-up input current
of the buck-boost converter is higher than the standard
Since the lead frame is solid copper, heat from the die is buck-mode regulator, and this may overload an input power
readily conducted through the leads to the printed circuit source with a current limit less than 1.5A. Using a delayed
board copper, which is acting as a heat sink. turn-on or an undervoltage lockout circuit (described in the
For best thermal performance, the ground pins and all the next section) would allow the input voltage to rise to a high
unconnected pins should be soldered to generous amounts enough level before the switcher would be allowed to turn
of printed circuit board copper, such as a ground plane. on.
Large areas of copper provide the best transfer of heat to the Because of the structural differences between the buck and
surrounding air. Copper on both sides of the board is also the buck-boost regulator topologies, the buck regulator de-
helpful in getting the heat away from the package, even if sign procedure section can not be used to select the inductor
there is no direct copper contact between the two sides. or the output capacitor. The recommended range of inductor
Thermal resistance numbers as low as 40˚C/W for the SO values for the buck-boost design is between 68 µH and 220
package, and 30˚C/W for the N package can be realized with µH, and the output capacitor values must be larger than what
a carefully engineered pc board. is normally required for buck designs. Low input voltages or
Included on the Switchers Made Simple design software is high output currents require a large value output capacitor
a more precise (non-linear) thermal model that can be used (in the thousands of micro Farads).
to determine junction temperature with different input-output The peak inductor current, which is the same as the peak
parameters or different component values. It can also calcu- switch current, can be calculated from the following formula:
late the heat sink thermal resistance required to maintain the
regulators junction temperature below the maximum operat-
ing temperature.

Additional Applications
Where fosc = 52 kHz. Under normal continuous inductor
INVERTING REGULATOR current operating conditions, the minimum VIN represents
the worst case. Select an inductor that is rated for the peak
Figure 10 shows a LM2575-12 in a buck-boost configuration current anticipated.
to generate a negative 12V output from a positive input
voltage. This circuit bootstraps the regulator’s ground pin to Also, the maximum voltage appearing across the regulator is
the negative output voltage, then by grounding the feedback the absolute sum of the input and output voltage. For a −12V
pin, the regulator senses the inverted output voltage and output, the maximum input voltage for the LM2575 is +28V,
regulates it to −12V. or +48V for the LM2575HV.
For an input voltage of 12V or more, the maximum available The Switchers Made Simple (version 3.3) design software
output current in this configuration is approximately 0.35A. At can be used to determine the feasibility of regulator designs
lighter loads, the minimum input voltage required drops to using different topologies, different input-output parameters,
approximately 4.7V. different components, etc.
The switch currents in this buck-boost configuration are
higher than in the standard buck-mode design, thus lowering

01147515

FIGURE 10. Inverting Buck-Boost Develops −12V

NEGATIVE BOOST REGULATOR Because of the boosting function of this type of regulator, the
Another variation on the buck-boost topology is the negative switch current is relatively high, especially at low input volt-
boost configuration. The circuit in Figure 11 accepts an input ages. Output load current limitations are a result of the
voltage ranging from −5V to −12V and provides a regulated maximum current rating of the switch. Also, boost regulators
−12V output. Input voltages greater than −12V will cause the can not provide current limiting load protection in the event of
output to rise above −12V, but will not damage the regulator. a shorted load, so some other means (such as a fuse) may
be necessary.

www.national.com 20

Datasheet pdf - http://www.DataSheet4U.net/

www.DataSheet.co.kr

LM1575/LM2575/LM2575HV
Additional Applications (Continued)

01147517
Note: Complete circuit not shown.
01147516
Typical Load Current Note: Pin numbers are for the TO-220 package.

200 mA for VIN = −5.2V

500 mA for VIN = −7V FIGURE 12. Undervoltage Lockout for Buck Circuit
Note: Pin numbers are for TO-220 package.

FIGURE 11. Negative Boost

UNDERVOLTAGE LOCKOUT
In some applications it is desirable to keep the regulator off
until the input voltage reaches a certain threshold. An und-
ervoltage lockout circuit which accomplishes this task is
shown in Figure 12, while Figure 13 shows the same circuit
applied to a buck-boost configuration. These circuits keep
the regulator off until the input voltage reaches a predeter-
mined level.
VTH ≈ VZ1 + 2VBE (Q1)
01147518
Note: Complete circuit not shown (see Figure 10).
DELAYED STARTUP
Note: Pin numbers are for the TO-220 package.
The ON /OFF pin can be used to provide a delayed startup
feature as shown in Figure 14. With an input voltage of 20V
and for the part values shown, the circuit provides approxi- FIGURE 13. Undervoltage Lockout
mately 10 ms of delay time before the circuit begins switch- for Buck-Boost Circuit
ing. Increasing the RC time constant can provide longer
delay times. But excessively large RC time constants can
cause problems with input voltages that are high in 60 Hz or
120 Hz ripple, by coupling the ripple into the ON /OFF pin.

ADJUSTABLE OUTPUT, LOW-RIPPLE

POWER SUPPLY
A 1A power supply that features an adjustable output voltage
is shown in Figure 15. An additional L-C filter that reduces
the output ripple by a factor of 10 or more is included in this
circuit.
01147519
Note: Complete circuit not shown.
Note: Pin numbers are for the TO-220 package.

FIGURE 14. Delayed Startup

21 www.national.com

Datasheet pdf - http://www.DataSheet4U.net/

www.DataSheet.co.kr

LM1575/LM2575/LM2575HV
Additional Applications (Continued)

01147520
Note: Pin numbers are for the TO-220 package.

FIGURE 15. 1.2V to 55V Adjustable 1A Power Supply with Low Output Ripple

Definition of Terms
BUCK REGULATOR
A switching regulator topology in which a higher voltage is 01147521

converted to a lower voltage. Also known as a step-down

switching regulator. FIGURE 16. Simple Model of a Real Capacitor

BUCK-BOOST REGULATOR Most standard aluminum electrolytic capacitors in the

A switching regulator topology in which a positive voltage is 100 µF–1000 µF range have 0.5Ω to 0.1Ω ESR. Higher-
converted to a negative voltage without a transformer. grade capacitors (“low-ESR”, “high-frequency”, or “low-
inductance”’) in the 100 µF–1000 µF range generally have
DUTY CYCLE (D) ESR of less than 0.15Ω.
Ratio of the output switch’s on-time to the oscillator period.
EQUIVALENT SERIES INDUCTANCE (ESL)
The pure inductance component of a capacitor (see Figure
16). The amount of inductance is determined to a large
extent on the capacitor’s construction. In a buck regulator,
this unwanted inductance causes voltage spikes to appear
on the output.

OUTPUT RIPPLE VOLTAGE

The AC component of the switching regulator’s output volt-
age. It is usually dominated by the output capacitor’s ESR
CATCH DIODE OR CURRENT STEERING DIODE
multiplied by the inductor’s ripple current (∆IIND). The peak-
The diode which provides a return path for the load current to-peak value of this sawtooth ripple current can be deter-
when the LM2575 switch is OFF. mined by reading the Inductor Ripple Current section of the
EFFICIENCY (η) Application hints.
The proportion of input power actually delivered to the load.
CAPACITOR RIPPLE CURRENT
RMS value of the maximum allowable alternating current at
which a capacitor can be operated continuously at a speci-
fied temperature.

STANDBY QUIESCENT CURRENT (ISTBY)

CAPACITOR EQUIVALENT SERIES RESISTANCE (ESR) Supply current required by the LM2575 when in the standby
The purely resistive component of a real capacitor’s imped- mode (ON /OFF pin is driven to TTL-high voltage, thus
ance (see Figure 16). It causes power loss resulting in turning the output switch OFF).
capacitor heating, which directly affects the capacitor’s op-
erating lifetime. When used as a switching regulator output INDUCTOR RIPPLE CURRENT (∆IIND)
filter, higher ESR values result in higher output ripple volt- The peak-to-peak value of the inductor current waveform,
ages. typically a sawtooth waveform when the regulator is operat-
ing in the continuous mode (vs. discontinuous mode).

www.national.com 22

Datasheet pdf - http://www.DataSheet4U.net/

www.DataSheet.co.kr

LM1575/LM2575/LM2575HV
Definition of Terms (Continued) nates. Inductor current is then limited only by the DC resis-
tance of the wire and the available source current.
CONTINUOUS/DISCONTINUOUS MODE OPERATION
Relates to the inductor current. In the continuous mode, the OPERATING VOLT MICROSECOND CONSTANT (E • Top)
inductor current is always flowing and never drops to zero, The product (in VoIt • µs) of the voltage applied to the inductor
vs. the discontinuous mode, where the inductor current and the time the voltage is applied. This E • Top constant is a
drops to zero for a period of time in the normal switching measure of the energy handling capability of an inductor and
cycle. is dependent upon the type of core, the core area, the
number of turns, and the duty cycle.
INDUCTOR SATURATION
The condition which exists when an inductor cannot hold any
more magnetic flux. When an inductor saturates, the induc-
tor appears less inductive and the resistive component domi-

23 www.national.com

Datasheet pdf - http://www.DataSheet4U.net/

www.DataSheet.co.kr

LM1575/LM2575/LM2575HV
Physical Dimensions inches (millimeters)
unless otherwise noted

16-Lead Ceramic Dual-in-Line (J)

Order Number LM1575J-3.3/883, LM1575J-5.0/883,
LM1575J-12/883, LM1575J-15/883, or LM1575J-ADJ/883
NS Package Number J16A

14-Lead Wide Surface Mount (WM)

Order Number LM2575M-5.0, LM2575HVM-5.0, LM2575M-12,
LM2575HVM-12, LM2575M-15, LM2575HVM-15,
LM2575M-ADJ or LM2575HVM-ADJ
NS Package Number M24B

www.national.com 24

Datasheet pdf - http://www.DataSheet4U.net/

www.DataSheet.co.kr

LM1575/LM2575/LM2575HV
Physical Dimensions inches (millimeters) unless otherwise noted (Continued)

16-Lead Molded DIP (N)

Order Number LM2575N-5.0, LM2575HVN-5.0, LM2575N-12, LM2575HVN-12,
LM2575N-15, LM2575HVN-15, LM2575N-ADJ or LM2575HVN-ADJ
NS Package Number N16A

5-Lead TO-220 (T)

Order Number LM2575T-3.3, LM2575HVT-3.3, LM2575T-5.0, LM2575HVT-5.0, LM2575T-12,
LM2575HVT-12, LM2575T-15, LM2575HVT-15, LM2575T-ADJ or LM2575HVT-ADJ
NS Package Number T05A

25 www.national.com

Datasheet pdf - http://www.DataSheet4U.net/

www.DataSheet.co.kr

LM1575/LM2575/LM2575HV
Physical Dimensions inches (millimeters) unless otherwise noted (Continued)

TO-263, Molded, 5-Lead Surface Mount

Order Number LM2575S-3.3, LM2575HVS-3.3, LM2575S-5.0, LM2575HVS-5.0, LM2575S-12,
LM2575HVS-12, LM2575S-15, LM2575HVS-15, LM2575S-ADJ or LM2575HVS-ADJ
NS Package Number TS5B

www.national.com 26

Datasheet pdf - http://www.DataSheet4U.net/

www.DataSheet.co.kr

LM1575/LM2575/LM2575HV Series SIMPLE SWITCHER 1A Step-Down Voltage Regulator

Physical Dimensions inches (millimeters) unless otherwise noted (Continued)

Bent, Staggered 5-Lead TO-220 (T)

Order Number LM2575T-3.3 Flow LB03, LM2575HVT-3.3 Flow LB03,
LM2575T-5.0 Flow LB03, LM2575HVT-5.0 Flow LB03,
LM2575T-12 Flow LB03, LM2575HVT-12 Flow LB03,
LM2575T-15 Flow LB03, LM2575HVT-15 Flow LB03,
LM2575T-ADJ Flow LB03 or LM2575HVT-ADJ Flow LB03
NS Package Number T05D

LIFE SUPPORT POLICY

NATIONAL’S PRODUCTS ARE NOT AUTHORIZED FOR USE AS CRITICAL COMPONENTS IN LIFE SUPPORT
DEVICES OR SYSTEMS WITHOUT THE EXPRESS WRITTEN APPROVAL OF THE PRESIDENT AND GENERAL
COUNSEL OF NATIONAL SEMICONDUCTOR CORPORATION. As used herein:
1. Life support devices or systems are devices or 2. A critical component is any component of a life
systems which, (a) are intended for surgical implant support device or system whose failure to perform
into the body, or (b) support or sustain life, and can be reasonably expected to cause the failure of
whose failure to perform when properly used in the life support device or system, or to affect its
accordance with instructions for use provided in the safety or effectiveness.
labeling, can be reasonably expected to result in a
significant injury to the user.
BANNED SUBSTANCE COMPLIANCE
National Semiconductor certifies that the products and packing materials meet the provisions of the Customer Products
Stewardship Specification (CSP-9-111C2) and the Banned Substances and Materials of Interest Specification
(CSP-9-111S2) and contain no ‘‘Banned Substances’’ as defined in CSP-9-111S2.
National Semiconductor National Semiconductor National Semiconductor National Semiconductor
Americas Customer Europe Customer Support Center Asia Pacific Customer Japan Customer Support Center
Support Center Fax: +49 (0) 180-530 85 86 Support Center Fax: 81-3-5639-7507
Email: new.feedback@nsc.com Email: europe.support@nsc.com Email: ap.support@nsc.com Email: jpn.feedback@nsc.com
Tel: 1-800-272-9959 Deutsch Tel: +49 (0) 69 9508 6208 Tel: 81-3-5639-7560
English Tel: +44 (0) 870 24 0 2171
www.national.com Français Tel: +33 (0) 1 41 91 8790

National does not assume any responsibility for use of any circuitry described, no circuit patent licenses are implied and National reserves the right at any time without notice to change said circuitry and specifications.

Datasheet pdf - http://www.DataSheet4U.net/