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PDF LM1575HV Data sheet ( Hoja de datos )
| Número de pieza | LM1575HV | |
| Descripción | 1A Step-Down Voltage Regulator | |
| Fabricantes | National Semiconductor | |
| Logotipo |  |
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June 1996
LM1575 LM1575HV LM2575 LM2575HV Series
SIMPLE SWITCHER 1A Step-Down Voltage Regulator
General Description
The LM2575 series of regulators are monolithic integrated
circuits that provide all the active functions for a step-down
(buck) switching regulator capable of driving a 1A load with
excellent line and load regulation These devices are avail-
able in fixed output voltages of 3 3V 5V 12V 15V and an
adjustable output version
Requiring a minimum number of external components
these regulators are simple to use and include internal fre-
quency compensation and a fixed-frequency oscillator
The LM2575 series offers a high-efficiency replacement for
popular three-terminal linear regulators It substantially re-
duces the size of the heat sink and in many cases no heat
sink is required
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
power supplies
Other features include a guaranteed g4% tolerance on out-
put voltage within specified input voltages and output load
conditions and g10% on the oscillator frequency External
shutdown is included featuring 50 mA (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
Features
Y 3 3V 5V 12V 15V and adjustable output versions
Y Adjustable version output voltage range
1 23V to 37V (57V for HV version) g4% max over
line and load conditions
Y Guaranteed 1A output current
Y Wide input voltage range 40V up to 60V
for HV version
Y Requires only 4 external components
Y 52 kHz fixed frequency internal oscillator
Y TTL shutdown capability low power standby mode
Y High efficiency
Y Uses readily available standard inductors
Y Thermal shutdown and current limit protection
Y Pa Product Enhancement tested
Applications
Y Simple high-efficiency step-down (buck) regulator
Y Efficient pre-regualtor for linear regulators
Y On-card switching regulators
Y Positive to negative converter (Buck-Boost)
Typical Application (Fixed Output Voltage Versions)
Note Pin numbers are for the TO-220 package
Block Diagram and Typical Application
TL H 11475 – 1
3 3V R2 e 1 7k
5V R2 e 3 1k
12V R2 e 8 84k
15V R2 e 11 3k
For ADJ Version
R1 e Open R2 e 0X
Note Pin numbers are for
the TO-220 package
Patent Pending
FIGURE 1
SIMPLE SWITCHER is a registered trademark of National Semiconductor Corporation
C1996 National Semiconductor Corporation TL H 11475
RRD-B30M76 Printed in U S A
TL H 11475 – 2
http www national com
1 page  
Electrical Characteristics (Notes) (Continued)
Note 9 Junction to ambient thermal resistance (no external heat sink) for the 5 lead TO-220 package mounted vertically with 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 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 approxmiately 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 iJA is 50 C W with 1 square inch of copper area iJA is 37 C W and with 1 6 or more square inches of copper area iJA 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 LM1575K LM1575HVK for current revision of military RETS SMD
Typical Performance Characteristics (Circuit ofFigure 2 )
Normalized Output Voltage
Line Regulation
Dropout Voltage
Current Limit
Quiescent Current
Standby
Quiescent Current
Oscillator Frequency
Switch Saturation
Voltage
Efficiency
TL H 11475 – 3
TL H 11475 – 31
5 http www national com
5 Page 
LM2575 Series Buck Regulator Design Procedure (Continued)
PROCEDURE (Adjustable Output Voltage Versions)
4 Catch Diode Selection (D1)
A The catch-diode current rating must be at least 1 2
times greater than the maximum load current Also if the
power supply design must withstand a continuous output
short the diode should have 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
5 Input Capacitor (CIN)
An aluminum or tantalum electrolytic bypass capacitor
located close to the regulator is needed for stable
operation
EXAMPLE (Adjustable Output Voltage Versions)
4 Catch Diode Selection (D1)
A For this example a 3A current rating is adequate
B Use a 40V MBR340 or 31DQ04 Schottky diode or any of the
suggested fast-recovery diodes in Figure 8
5 Input Capacitor (CIN)
A 100 mF aluminum electrolytic capacitor located near the input
and ground pins provides sufficient bypassing
To further simplify the buck regulator
design procedure National Semicon-
ductor is making available computer
design software to be used with the
Simple Switcher line of switching regu-
lators Switchers Made Simple (ver-
sion 3 3) is available on a (3 ) disk-
ette for IBM compatible computers
from a National Semiconductor sales
office in your area
Schottky
VR 1A
3A
Fast Recovery
1A 3A
20V 1N5817
1N5820
MBR120P
MBR320
SR102
SR302
30V 1N5818
1N5821
MBR130P
MBR330
11DQ03
SR103
31DQ03
SR303
The following
diodes are all
The following
diodes are all
40V 1N5819
IN5822
rated to 100V
rated to 100V
MBR140P
MBR340
11DQ04
31DQ04
11DF1
31DF1
SR104
SR304
MUR110
MURD310
50V MBR150
MBR350
HER102
HER302
11DQ05
31DQ05
SR105
SR305
60V MBR160
11DQ06
SR106
MBR360
31DQ06
SR306
FIGURE 8 Diode Selection Guide
Inductor
Code
L100
L150
L220
L330
L470
L680
H150
H220
H330
H470
H680
H1000
H1500
H2200
Inductor
Value
100 mH
150 mH
220 mH
330 mH
470 mH
680 mH
150 mH
220 mH
330 mH
470 mH
680 mH
1000 mH
1500 mH
2200 mH
Schott
(Note 1)
67127000
67127010
67127020
67127030
67127040
67127050
67127060
67127070
67127080
67127090
67127100
67127110
67127120
67127130
Pulse Eng
(Note 2)
PE-92108
PE-53113
PE-52626
PE-52627
PE-53114
PE-52629
PE-53115
PE-53116
PE-53117
PE-53118
PE-53119
PE-53120
PE-53121
PE-53122
Note 1 Schott Corp (612) 475-1173 1000 Parkers Lake Rd Wayzata MN 55391
Note 2 Pulse Engineering (619) 674-8100 P O Box 12236 San Diego CA 92112
Note 3 Renco Electronics Inc (516) 586-5566 60 Jeffryn Blvd East Deer Park NY 11729
FIGURE 9 Inductor Selection by Manufacturer’s Part Number
Renco
(Note 3)
RL2444
RL1954
RL1953
RL1952
RL1951
RL1950
RL2445
RL2446
RL2447
RL1961
RL1960
RL1959
RL1958
RL2448
11 http www national com
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