NSC LM2596-5.0MDC, LM2596-3.3MWC, LM2596-5.0MWC Datasheet
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 available in fixed output voltages of 3.3V, 5V, 12V, and an adjustable output version.
Requiring aminimum 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 regulators. 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 output voltage under specified input voltage and output load
conditions, and
±
15% on the oscillator frequency. External
shutdown is included, featuring typically 80 µA standby current. 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 (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 Voltage 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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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 −65˚C to +150˚C
ESD Susceptibility
Human Body Model (Note 2) 2 kV
Lead Temperature
S Package
Vapor Phase (60 sec.) +215˚C
Infrared (10 sec.) +245˚C
T Package (Soldering, 10 sec.) +260˚C
Maximum Junction Temperature +150˚C
Operating Conditions
Temperature Range −40˚C ≤ TJ≤ +125˚C
Supply Voltage 4.5V to 40V
LM2596-3.3
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
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 ≤ VIN≤ 40V, 0.2A ≤ I
LOAD
≤ 3A 3.3 V
3.168/3.135 V(min)
3.432/3.465 V(max)
η Efficiency V
IN
= 12V, I
LOAD
=3A 73 %
LM2596-5.0
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
LM2596-5.0
Units
(Limits)
Typ
(Note 3)
Limit
(Note 4)
SYSTEM PARAMETERS (Note 5) Test Circuit
Figure 1
V
OUT
Output Voltage 7V ≤ VIN≤ 40V, 0.2A ≤ I
LOAD
≤ 3A 5.0 V
4.800/4.750 V(min)
5.200/5.250 V(max)
η Efficiency V
IN
= 12V, I
LOAD
=3A 80 %
LM2596-12
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
LM2596-12
Units
(Limits)
Typ
(Note 3)
Limit
(Note 4)
SYSTEM PARAMETERS (Note 5) Test Circuit
Figure 1
V
OUT
Output Voltage 15V ≤ VIN≤ 40V, 0.2A ≤ I
LOAD
≤ 3A 12.0 V
11.52/11.40 V(min)
12.48/12.60 V(max)
η Efficiency V
IN
= 25V, I
LOAD
=3A 90 %
LM2596
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LM2596-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
LM2596-ADJ
Units
(Limits)
Typ
(Note 3)
Limit
(Note 4)
SYSTEM PARAMETERS (Note 5) Test Circuit
Figure 1
V
FB
Feedback Voltage 4.5V ≤ VIN≤ 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)
η Efficiency V
IN
= 12V, V
OUT
= 3V, I
LOAD
=3A 73 %
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 Temperature Range. Unless otherwise specified, V
IN
= 12V for the 3.3V, 5V, and Adjustable version and VIN= 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, VFB= 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 µA(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 µA
200/250 µA(max)
θ
JC
Thermal Resistance TO-220 or TO-263 Package, Junction to Case 2 ˚C/W
θ
JA
TO-220 Package, Junction to Ambient (Note 11) 50 ˚C/W
θ
JA
TO-263 Package, Junction to Ambient (Note 12) 50 ˚C/W
θ
JA
TO-263 Package, Junction to Ambient (Note 13) 30 ˚C/W
θ
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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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, V
IN
= 12V for the 3.3V, 5V, and Adjustable version and VIN= 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 µA
15 µA(max)
I
L
V
LOGIC
= 0.5V (Regulator ON) 0.02 µA
5 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: The human body model is a 100 pF capacitor discharged through a 1.5k resistor into each pin.
Note 3: Typical numbers are at 25˚C 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.WhentheLM2596is 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. SeeApplication Information in this data sheet and the thermal
model in Switchers Made Simple
™
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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Typical Performance Characteristics (Circuit of
Figure 1
) (Continued)
Switch Saturation
Voltage Switch Current Limit Dropout Voltage
01258307 01258308
01258309
Operating
Quiescent Current
Shutdown
Quiescent Current
Minimum Operating
Supply Voltage
01258310 01258311
01258312
ON /OFF Threshold
Voltage
ON /OFF Pin
Current (Sinking) Switching Frequency
01258313
01258314
01258315
LM2596
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Typical Performance Characteristics (Circuit of
Figure 1
) (Continued)
Feedback Pin
Bias Current
01258316
LM2596
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Typical Performance Characteristics
Continuous Mode Switching Waveforms
V
IN
= 20V, V
OUT
= 5V, I
LOAD
=2A
L = 32 µH, C
OUT
= 220 µF, C
OUT
ESR=50mΩ
Discontinuous Mode Switching Waveforms
V
IN
= 20V, V
OUT
= 5V, I
LOAD
= 500 mA
L = 10 µH, C
OUT
= 330 µF, C
OUT
ESR=45mΩ
01258317
Horizontal Time Base: 2 µs/div.
A: Output Pin Voltage, 10V/div.
B: Inductor Current 1A/div.
C: Output Ripple Voltage, 50 mV/div.
01258318
Horizontal Time Base: 2 µs/div.
A: Output Pin Voltage, 10V/div.
B: Inductor Current 0.5A/div.
C: Output Ripple Voltage, 100 mV/div.
Load Transient Response for Continuous Mode
V
IN
= 20V, V
OUT
= 5V, I
LOAD
= 500 mA to 2A
L = 32 µH, C
OUT
= 220 µF, C
OUT
ESR=50mΩ
Load Transient Response for Discontinuous Mode
V
IN
= 20V, V
OUT
= 5V, I
LOAD
= 500 mA to 2A
L = 10 µH, C
OUT
= 330 µF, C
OUT
ESR=45mΩ
01258319
Horizontal Time Base: 100 µs/div.
A: Output Voltage, 100 mV/div. (AC)
B: 500 mA to 2A Load Pulse
01258320
Horizontal Time Base: 200 µs/div.
A: Output Voltage, 100 mV/div. (AC)
B: 500 mA to 2A Load Pulse
Test Circuit and Layout Guidelines
Fixed Output Voltage Versions
01258322
CIN—470 µF, 50V, Aluminum Electrolytic Nichicon “PL Series”
C
OUT
—220 µF, 25V Aluminum Electrolytic, Nichicon “PL Series”
D1 — 5A, 40V Schottky Rectifier, 1N5825
L1 — 68 µH, L38
LM2596
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Test Circuit and Layout Guidelines (Continued)
As in any switching regulator, layout is very important. Rapidly switching currents associated with wiring inductance can
generate voltage transients which can cause problems. For
minimal inductance and ground loops, the wires indicated by
heavy lines should be wide printed circuit traces and
should be kept as short as possible. For best results,
external components should be located as close to the
switcher lC as possible using ground plane construction or
single point grounding.
If open core inductors are used, special care must be
taken as to the location and positioning of this type of inductor.Allowing the inductor flux to intersect sensitive feedback,
lC groundpath and C
OUT
wiring can cause problems.
When using the adjustable version, special care must be
taken as to the location of the feedback resistors and the
associated wiring. Physically locate both resistors near the
IC, and route the wiring away from the inductor, especially an
open core type of inductor. (See application section for more
information.)
Adjustable Output Voltage Versions
01258323
where V
REF
= 1.23V
Select R1to be approximately 1 kΩ, use a 1% resistor for best stability.
C
IN
—470 µF, 50V, Aluminum Electrolytic Nichicon “PL Series”
C
OUT
—220 µF, 35V Aluminum Electrolytic, Nichicon “PL Series”
D1 — 5A, 40V Schottky Rectifier, 1N5825
L1 — 68 µH, L38
R1 — 1 kΩ,1%
C
FF
—See Application Information Section
FIGURE 1. Standard Test Circuits and Layout Guides
LM2596
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LM2596 Series Buck Regulator Design Procedure (Fixed Output)
PROCEDURE (Fixed Output Voltage Version) EXAMPLE (Fixed Output Voltage Version)
Given:
V
OUT
= Regulated Output Voltage (3.3V, 5V or 12V)
V
IN
(max) = Maximum DC Input Voltage
I
LOAD
(max) = Maximum Load Current
Given:
V
OUT
=5V
V
IN
(max) = 12V
I
LOAD
(max) = 3A
1. Inductor Selection (L1)
A. Select the correct inductor value selection guide from Fig-
ures
Figure 4,Figure 5
,or
Figure 6
. (Output voltages of 3.3V,
5V, or 12V respectively.)For all other voltages, see the design
procedure for the adjustable version.
B. From the inductor value selection guide, identify the inductance region intersected by the Maximum Input Voltage line
and the Maximum Load Current line. Each region is identified
by an inductance value and an inductor code (LXX).
C. Select an appropriate inductor from the four manufacturer’s
part numbers listed in
Figure 8
.
1. Inductor Selection (L1)
A. Use the inductor selection guide for the 5V version shown
in
Figure 5
.
B. From the inductor value selection guide shown in
Figure 5
,
the inductance region intersected by the 12V horizontal line
and the 3A vertical line is 33 µH, and the inductor code is L40.
C. The inductance value required is 33 µH. From the table in
Figure 8
, go to the L40 line and choose an inductor part
number from any of the four manufacturers shown. (In most
instance, both through hole and surface mount inductors are
available.)
2. Output Capacitor Selection (C
OUT
)
A. In the majority of applications, low ESR (Equivalent Series
Resistance) electrolytic capacitors between 82 µF and 820 µF
and low ESR solid tantalum capacitors between 10 µF and
470 µF provide the best results. This capacitor should be
located close to the IC using short capacitor leads and short
copper traces. Do not use capacitors larger than 820 µF .
For additional information, see section on output capacitors in application information section.
B. To simplify the capacitor selection procedure, refer to the
quick design component selection table shown in
Figure 2
.
This table contains different input voltages, output voltages,
and load currents, and lists various inductors and output capacitors that will provide the best design solutions.
C. The capacitor voltage rating for electrolytic capacitors
should be at least 1.5 times greater than the output voltage,
and often much higher voltage ratings are needed to satisfy
the low ESR requirements for low output ripple voltage.
D. For computer aided design software, see
Switchers Made
Simple
™
version 4.3 or later.
2. Output Capacitor Selection (C
OUT
)
A. See section on output capacitors in application information section.
B. From the quick design component selection table shown in
Figure 2
, locate the 5V output voltage section. In the load
current column, choose the load current line that is closest to
the current needed in your application, for this example, use
the 3A line. In the maximum input voltage column, select the
line that covers the input voltage needed in your application, in
this example, use the 15V line. Continuing on this line are
recommended inductors and capacitors that will provide the
best overall performance.
The capacitor list contains both through hole electrolytic and
surface mount tantalum capacitors from four different capacitor manufacturers. It is recommended that both the manufacturers and the manufacturer’s series that are listed in the table
be used.
In this example aluminum electrolytic capacitors from several
different manufacturers are available with the range of ESR
numbers needed.
330 µF 35V Panasonic HFQ Series
330 µF 35V Nichicon PL Series
C. For a 5V output, a capacitor voltage rating at least 7.5V or
more is needed. But even a low ESR, switching grade, 220 µF
10V aluminum electrolytic capacitor would exhibit approximately 225 mΩ of ESR (see the curve in
Figure 14
for the ESR
vs voltage rating). This amount of ESR would result in relatively high output ripple voltage. To reduce the ripple to 1% of
the output voltage, or less, a capacitor with a higher value or
with a higher voltage rating (lower ESR) should be selected. A
16V or 25V capacitor will reduce the ripple voltage by approximately half.
LM2596
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