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 A 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 A
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
(Fixed Output Voltage
Versions)
01258301
SIMPLE SWITCHER
and
Switchers Made Simple
are registered trademarks of National Semiconductor Corporation.
May 2002
LM2596
SIMPLE
SWITCHER
Power
Converter
150
kHz
3A
Step-Down
V
oltage
Regulator
2002 National Semiconductor Corporation
DS012583
www.national.com
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
Order Number LM2596T-3.3, LM2596T-5.0,
LM2596T-12 or LM2596T-ADJ
See NS Package Number T05D
01258303
Order Number LM2596S-3.3, LM2596S-5.0,
LM2596S-12 or LM2596S-ADJ
See NS Package Number TS5B
LM2596
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2
Absolute Maximum Ratings
(Note 1)
If Military/Aerospace specified devices are required,
please contact the National Semiconductor Sales Office/
Distributors for availability and specifications.
Maximum Supply Voltage
45V
ON /OFF Pin Input Voltage
-0.3
V
+25V
Feedback Pin Voltage
-0.3
V
+25V
Output Voltage to Ground
(Steady State)
-1V
Power Dissipation
Internally limited
Storage Temperature Range
-65C to +150C
ESD Susceptibility
Human Body Model (Note 2)
2 kV
Lead Temperature
S Package
Vapor Phase (60 sec.)
+215C
Infrared (10 sec.)
+245C
T Package (Soldering, 10 sec.)
+260C
Maximum Junction Temperature
+150C
Operating Conditions
Temperature Range
-40C
T
J
+125C
Supply Voltage
4.5V to 40V
LM2596-3.3
Electrical Characteristics
Specifications with standard type face are for T
J
= 25C, and those with boldface type apply over full Operating Tempera-
ture Range
Symbol
Parameter
Conditions
LM2596-3.3
Units
(Limits)
Typ
(Note 3)
Limit
(Note 4)
SYSTEM PARAMETERS (Note 5) Test Circuit
Figure 1
V
OUT
Output Voltage
4.75V
V
IN
40V, 0.2A
I
LOAD
3A
3.3
V
3.168/3.135
V(min)
3.432/3.465
V(max)
Efficiency
V
IN
= 12V, I
LOAD
= 3A
73
%
LM2596-5.0
Electrical Characteristics
Specifications with standard type face are for T
J
= 25C, and those with boldface type apply over full Operating Tempera-
ture Range
Symbol
Parameter
Conditions
LM2596-5.0
Units
(Limits)
Typ
(Note 3)
Limit
(Note 4)
SYSTEM PARAMETERS (Note 5) Test Circuit
Figure 1
V
OUT
Output Voltage
7V
V
IN
40V, 0.2A
I
LOAD
3A
5.0
V
4.800/4.750
V(min)
5.200/5.250
V(max)
Efficiency
V
IN
= 12V, I
LOAD
= 3A
80
%
LM2596-12
Electrical Characteristics
Specifications with standard type face are for T
J
= 25C, and those with boldface type apply over full Operating Tempera-
ture Range
Symbol
Parameter
Conditions
LM2596-12
Units
(Limits)
Typ
(Note 3)
Limit
(Note 4)
SYSTEM PARAMETERS (Note 5) Test Circuit
Figure 1
V
OUT
Output Voltage
15V
V
IN
40V, 0.2A
I
LOAD
3A
12.0
V
11.52/11.40
V(min)
12.48/12.60
V(max)
Efficiency
V
IN
= 25V, I
LOAD
= 3A
90
%
LM2596
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3
LM2596-ADJ
Electrical Characteristics
Specifications with standard type face are for T
J
= 25C, and those with boldface type apply over full Operating Tempera-
ture Range
Symbol
Parameter
Conditions
LM2596-ADJ
Units
(Limits)
Typ
(Note 3)
Limit
(Note 4)
SYSTEM PARAMETERS (Note 5) Test Circuit
Figure 1
V
FB
Feedback Voltage
4.5V
V
IN
40V, 0.2A
I
LOAD
3A
1.230
V
V
OUT
programmed for 3V. Circuit of
Figure 1
1.193/1.180
V(min)
1.267/1.280
V(max)
Efficiency
V
IN
= 12V, V
OUT
= 3V, I
LOAD
= 3A
73
%
All Output Voltage Versions
Electrical Characteristics
Specifications with standard type face are for T
J
= 25C, 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
Symbol
Parameter
Conditions
LM2596-XX
Units
(Limits)
Typ
(Note 3)
Limit
(Note 4)
DEVICE PARAMETERS
I
b
Feedback Bias Current
Adjustable Version Only, V
FB
= 1.3V
10
nA
50/100
nA (max)
f
O
Oscillator Frequency
(Note 6)
150
kHz
127/110
kHz(min)
173/173
kHz(max)
V
SAT
Saturation Voltage
I
OUT
= 3A (Notes 7, 8)
1.16
V
1.4/1.5
V(max)
DC
Max Duty Cycle (ON)
(Note 8)
100
%
Min Duty Cycle (OFF)
(Note 9)
0
I
CL
Current Limit
Peak Current (Notes 7, 8)
4.5
A
3.6/3.4
A(min)
6.9/7.5
A(max)
I
L
Output Leakage Current
Output = 0V (Notes 7, 9)
50
A(max)
Output = -1V (Note 10)
2
mA
30
mA(max)
I
Q
Quiescent Current
(Note 9)
5
mA
10
mA(max)
I
STBY
Standby Quiescent Current
ON/OFF pin = 5V (OFF)
(Note 10)
80
A
200/250
A(max)
JC
Thermal Resistance
TO-220 or TO-263 Package, Junction to Case
2
C/W
JA
TO-220 Package, Junction to Ambient (Note 11)
50
C/W
JA
TO-263 Package, Junction to Ambient (Note 12)
50
C/W
JA
TO-263 Package, Junction to Ambient (Note 13)
30
C/W
JA
TO-263 Package, Junction to Ambient (Note 14)
20
C/W
ON/OFF CONTROL Test Circuit
Figure 1
ON /OFF Pin Logic Input
1.3
V
V
IH
Threshold Voltage
Low (Regulator ON)
0.6
V(max)
V
IL
High (Regulator OFF)
2.0
V(min)
LM2596
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4
All Output Voltage Versions
Electrical Characteristics
(Continued)
Specifications with standard type face are for T
J
= 25C, 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
Symbol
Parameter
Conditions
LM2596-XX
Units
(Limits)
Typ
(Note 3)
Limit
(Note 4)
I
H
ON /OFF Pin Input Current
V
LOGIC
= 2.5V (Regulator OFF)
5
A
15
A(max)
I
L
V
LOGIC
= 0.5V (Regulator ON)
0.02
A
5
A(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: The human body model is a 100 pF capacitor discharged through a 1.5k resistor into each pin.
Note 3: Typical numbers are at 25C and represent the most likely norm.
Note 4: 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. All limits are used to
calculate Average Outgoing Quality Level (AOQL).
Note 5: External components such as the catch diode, inductor, input and output capacitors, and voltage programming resistors can affect switching regulator
system performance. When the LM2596 is used as shown in the
Figure 1
test circuit, system performance will be as shown in system parameters section of Electrical
Characteristics.
Note 6: The switching frequency is reduced when the second stage current limit is activated.
Note 7: No diode, inductor or capacitor connected to output pin.
Note 8: Feedback pin removed from output and connected to 0V to force the output transistor switch ON.
Note 9: Feedback pin removed from output and connected to 12V for the 3.3V, 5V, and the ADJ. version, and 15V for the 12V version, to force the output transistor
switch OFF.
Note 10: V
IN
= 40V.
Note 11: Junction to ambient thermal resistance (no external heat sink) for the TO-220 package mounted vertically, with the leads soldered to a printed circuit board
with (1 oz.) copper area of approximately 1 in
2
.
Note 12: Junction to ambient thermal resistance with the TO-263 package tab soldered to a single printed circuit board with 0.5 in
2
of (1 oz.) copper area.
Note 13: Junction to ambient thermal resistance with the TO-263 package tab soldered to a single sided printed circuit board with 2.5 in
2
of (1 oz.) copper area.
Note 14: Junction to ambient thermal resistance with the TO-263 package tab soldered to a double sided printed circuit board with 3 in
2
of (1 oz.) copper area on
the LM2596S side of the board, and approximately 16 in
2
of copper on the other side of the p-c board. See Application Information in this data sheet and the thermal
model in Switchers Made Simple
TM
version 4.3 software.
Typical Performance Characteristics
(Circuit of
Figure 1)
Normalized
Output Voltage
Line Regulation
Efficiency
01258304
01258305
01258306
LM2596
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