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LM2596 SIMPLE SWITCHER Power Converter 150 kHz 3A Step-Down Voltage Regulator
May 2002
LM2596
SIMPLE SWITCHER
®
Power Converter 150 kHz
3A Step-Down Voltage Regulator
General Description
The LM2596 series of regulators are monolithic integrated
circuits that provide all the active functions for a step-down
(buck) switching regulator, capable of driving a 3A load with
excellent line and load regulation. These devices are avail-
able in fixed output voltages of 3.3V, 5V, 12V, and an adjust-
able output version.
Requiring a minimum number of external components, these
regulators are simple to use and include internal frequency
compensation
†
, and a fixed-frequency oscillator.
The LM2596 series operates at a switching frequency of
150 kHz thus allowing smaller sized filter components than
what would be needed with lower frequency switching regu-
lators. Available in a standard 5-lead TO-220 package with
several different lead bend options, and a 5-lead TO-263
surface mount package.
A standard series of inductors are available from several
different manufacturers optimized for use with the LM2596
series. This feature greatly simplifies the design of
switch-mode power supplies.
Other features include a guaranteed
±
4% tolerance on out-
put voltage under specified input voltage and output load
conditions, and
±
15% on the oscillator frequency. External
shutdown is included, featuring typically 80 µA standby cur-
rent. Self protection features include a two stage frequency
reducing current limit for the output switch and an over
temperature shutdown for complete protection under fault
conditions.
Features
n
3.3V, 5V, 12V, and adjustable output versions
n
Adjustable version output voltage range, 1.2V to 37V
±
4% max over line and load conditions
n
Available in TO-220 and TO-263 packages
n
Guaranteed 3A output load current
n
Input voltage range up to 40V
n
Requires only 4 external components
n
Excellent line and load regulation specifications
n
150 kHz fixed frequency internal oscillator
n
TTL shutdown capability
n
Low power standby mode, I
Q
typically 80 µA
n
High efficiency
n
Uses readily available standard inductors
n
Thermal shutdown and current limit protection
Applications
n
Simple high-efficiency step-down (buck) regulator
n
On-card switching regulators
n
Positive to negative converter
Note:
†
Patent Number 5,382,918.
Typical Application
Versions)
(Fixed Output Voltage
01258301
SIMPLE SWITCHER
®
and
Switchers Made Simple
®
are registered trademarks of National Semiconductor Corporation.
© 2002 National Semiconductor Corporation
DS012583
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LM2596
Connection Diagrams and Ordering Information
Bent and Staggered Leads, Through Hole
Package
5-Lead TO-220 (T)
Surface Mount Package
5-Lead TO-263 (S)
01258302
01258303
Order Number LM2596T-3.3, LM2596T-5.0,
LM2596T-12 or LM2596T-ADJ
See NS Package Number T05D
Order Number LM2596S-3.3, LM2596S-5.0,
LM2596S-12 or LM2596S-ADJ
See NS Package Number TS5B
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2
LM2596
Absolute Maximum Ratings
(Note 1)
Human Body Model (Note 2)
Lead Temperature
S Package
Vapor Phase (60 sec.)
Infrared (10 sec.)
T Package (Soldering, 10 sec.)
Maximum Junction Temperature
2 kV
If Military/Aerospace specified devices are required,
please contact the National Semiconductor Sales Office/
Distributors for availability and specifications.
Maximum Supply Voltage
ON /OFF Pin Input Voltage
Feedback Pin Voltage
Output Voltage to Ground
(Steady State)
Power Dissipation
Storage Temperature Range
ESD Susceptibility
−1V
Internally limited
−65˚C to +150˚C
45V
−0.3
≤
V
≤
+25V
−0.3
≤
V
≤+25V
+215˚C
+245˚C
+260˚C
+150˚C
Operating Conditions
Temperature Range
Supply Voltage
−40˚C
≤
T
J
≤
+125˚C
4.5V to 40V
LM2596-3.3
Electrical Characteristics
Specifications with standard type face are for T
J
= 25˚C, and those with
boldface type
apply over
full Operating Tempera-
ture Range
LM2596-3.3
Symbol
Parameter
Conditions
Typ
(Note 3)
3.3
3.168/3.135
3.432/3.465
η
Efficiency
V
IN
= 12V, I
LOAD
= 3A
73
Limit
(Note 4)
Units
(Limits)
SYSTEM PARAMETERS
(Note 5) Test Circuit
Figure 1
V
OUT
Output Voltage
4.75V
≤
V
IN
≤
40V, 0.2A
≤
I
LOAD
≤
3A
V
V(min)
V(max)
%
LM2596-5.0
Electrical Characteristics
Specifications with standard type face are for T
J
= 25˚C, and those with
boldface type
apply over
full Operating Tempera-
ture Range
LM2596-5.0
Symbol
Parameter
Conditions
Typ
(Note 3)
5.0
4.800/4.750
5.200/5.250
η
Efficiency
V
IN
= 12V, I
LOAD
= 3A
80
Limit
(Note 4)
Units
(Limits)
SYSTEM PARAMETERS
(Note 5) Test Circuit
Figure 1
V
OUT
Output Voltage
7V
≤
V
IN
≤
40V, 0.2A
≤
I
LOAD
≤
3A
V
V(min)
V(max)
%
LM2596-12
Electrical Characteristics
Specifications with standard type face are for T
J
= 25˚C, and those with
boldface type
apply over
full Operating Tempera-
ture Range
LM2596-12
Symbol
Parameter
Conditions
Typ
(Note 3)
12.0
11.52/11.40
12.48/12.60
η
Efficiency
V
IN
= 25V, I
LOAD
= 3A
90
Limit
(Note 4)
Units
(Limits)
SYSTEM PARAMETERS
(Note 5) Test Circuit
Figure 1
V
OUT
Output Voltage
15V
≤
V
IN
≤
40V, 0.2A
≤
I
LOAD
≤
3A
V
V(min)
V(max)
%
3
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LM2596
LM2596-ADJ
Electrical Characteristics
Specifications with standard type face are for T
J
= 25˚C, and those with
boldface type
apply over
full Operating Tempera-
ture Range
LM2596-ADJ
Symbol
Parameter
Conditions
Typ
(Note 3)
1.230
1.193/1.180
1.267/1.280
η
Efficiency
V
IN
= 12V, V
OUT
= 3V, I
LOAD
= 3A
73
Limit
(Note 4)
Units
(Limits)
SYSTEM PARAMETERS
(Note 5) Test Circuit
Figure 1
V
FB
Feedback Voltage
4.5V
≤
V
IN
≤
40V, 0.2A
≤
I
LOAD
≤
3A
V
OUT
programmed for 3V. Circuit of
Figure 1
V
V(min)
V(max)
%
All Output Voltage Versions
Electrical Characteristics
Specifications with standard type face are for T
J
= 25˚C, and those with
boldface type
apply over
full Operating Tempera-
ture Range.
Unless otherwise specified, V
IN
= 12V for the 3.3V, 5V, and Adjustable version and V
IN
= 24V for the 12V ver-
sion. I
LOAD
= 500 mA
LM2596-XX
Symbol
Parameter
Conditions
Typ
(Note 3)
10
50/100
f
O
Oscillator Frequency
(Note 6)
150
127/110
173/173
V
SAT
DC
I
CL
Saturation Voltage
Max Duty Cycle (ON)
Min Duty Cycle (OFF)
Current Limit
I
OUT
= 3A (Notes 7, 8)
(Note 8)
(Note 9)
Peak Current (Notes 7, 8)
1.16
1.4/1.5
100
0
4.5
3.6/3.4
6.9/7.5
I
L
Output Leakage Current
Output = 0V (Notes 7, 9)
Output = −1V (Note 10)
I
Q
I
STBY
θ
JC
θ
JA
θ
JA
θ
JA
θ
JA
ON /OFF Pin Logic Input
V
IH
V
IL
Threshold Voltage
Low (Regulator ON)
High (Regulator OFF)
Quiescent Current
Standby Quiescent Current
Thermal Resistance
(Note 9)
ON/OFF pin = 5V (OFF)
(Note 10)
2
30
5
10
80
200/250
TO-220 or TO-263 Package, Junction to Case
TO-220 Package, Junction to Ambient (Note 11)
TO-263 Package, Junction to Ambient (Note 12)
TO-263 Package, Junction to Ambient (Note 13)
TO-263 Package, Junction to Ambient (Note 14)
2
50
50
30
20
1.3
0.6
2.0
50
A
A(min)
A(max)
µA(max)
mA
mA(max)
mA
mA(max)
µA
µA(max)
˚C/W
˚C/W
˚C/W
˚C/W
˚C/W
V
V(max)
V(min)
Limit
(Note 4)
Units
(Limits)
DEVICE PARAMETERS
I
b
Feedback Bias Current
Adjustable Version Only, V
FB
= 1.3V
nA
nA (max)
kHz
kHz(min)
kHz(max)
V
V(max)
%
ON/OFF CONTROL
Test Circuit
Figure 1
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