TI1 LM2595SX-3.3/NOPB Lm2595 simple switcherâ® power converter 150 khz 1a step-down voltage regulator Datasheet

LM2595
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LM2595 SIMPLE SWITCHER® Power Converter 150 kHz 1A Step-Down Voltage Regulator
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FEATURES
DESCRIPTION
•
•
The LM2595 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 available in fixed output
voltages of 3.3V, 5V, 12V, and an adjustable output
version.
1
23
•
•
•
•
•
•
•
•
•
•
•
3.3V, 5V, 12V, and Adjustable Output Versions
Adjustable Version Output Voltage Range,
1.2V to 37V ±4% Max Over Line and Load
Conditions
Available in TO-220 and TO-263 (Surface
Mount) Packages
Ensured 1A Output Load Current
Input Voltage Range Up to 40V
Requires Only 4 External Components
Excellent Line and Load Regulation
Specifications
150 kHz Fixed Frequency Internal Oscillator
TTL Shutdown Capability
Low Power Standby Mode, IQ Typically 85 μA
High Efficiency
Uses Readily Available Standard Inductors
Thermal Shutdown and Current Limit
Protection
APPLICATIONS
•
•
•
•
Simple High-Efficiency Step-Down (Buck)
Regulator
Efficient Pre-Regulator for Linear Regulators
On-Card Switching Regulators
Positive to Negative Converter
Requiring a minimum number of external
components, these regulators are simple to use and
include internal frequency compensation†, and a
fixed-frequency oscillator.
The LM2595 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. Typically, for output voltages
less than 12V, and ambient temperatures less than
50°C, no heat sink is required.
A standard series of inductors are available from
several different manufacturers optimized for use with
the LM2595 series. This feature greatly simplifies the
design of switch-mode power supplies.
Other features include an ensured ±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 85 μA stand-by 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.
† Patent Number 5,382,918.
Typical Application
(Fixed Output Voltage Versions)
Connection Diagrams
1
2
3
Please be aware that an important notice concerning availability, standard warranty, and use in critical applications of
Texas Instruments semiconductor products and disclaimers thereto appears at the end of this data sheet.
SIMPLE SWITCHER, Switchers Made Simple are registered trademarks of Texas Instruments.
All other trademarks are the property of their respective owners.
PRODUCTION DATA information is current as of publication date.
Products conform to specifications per the terms of the Texas
Instruments standard warranty. Production processing does not
necessarily include testing of all parameters.
Copyright © 1999–2013, Texas Instruments Incorporated
LM2595
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Figure 1. Bent and Staggered Leads, Through
Hole Package
5–Lead TO-220 (NDH)
Figure 3. 16-Lead Ceramic Dual-in-Line Package
(NFE)
Figure 2. Surface Mount Package
5-Lead TO-263 (KTT)
These devices have limited built-in ESD protection. The leads should be shorted together or the device placed in conductive foam
during storage or handling to prevent electrostatic damage to the MOS gates.
Absolute Maximum Ratings
(1) (2)
Maximum Supply Voltage
45V
ON /OFF Pin Input Voltage
−0.3 ≤ V ≤ +25V
Feedback Pin Voltage
−0.3 ≤ V ≤ +25V
Output Voltage to Ground
−1V
(Steady State)
Power Dissipation
Internally limited
−65°C to +150°C
Storage Temperature Range
ESD Susceptibility
(3)
2 kV
Vapor Phase (60 sec.)
+215°C
Infrared (10 sec.)
+245°C
Human Body Model
Lead Temperature
KTT Package
NDH Package (Soldering, 10 sec.)
+260°C
Maximum Junction Temperature
+150°C
(1)
(2)
(3)
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 ensure specific performance limits. For ensured specifications and test
conditions, see the Electrical Characteristics.
If Military/Aerospace specified devices are required, please contact the Texas Instruments Sales Office/ Distributors for availability and
specifications.
The human body model is a 100 pF capacitor discharged through a 1.5k resistor into each pin.
Operating Conditions
−40°C ≤ TJ ≤ +125°C
Temperature Range
Supply Voltage
2
4.5V to 40V
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LM2595-3.3 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
LM2595-3.3
Typ
Limit
(1)
SYSTEM PARAMETERS
VOUT
η
(3)
(3)
(2)
Test Circuit Figure 21
4.75V ≤ VIN ≤ 40V, 0.1A ≤ ILOAD ≤ 1A
Output Voltage
Efficiency
(1)
(2)
Units
(Limits)
VIN = 12V, ILOAD = 1A
3.3
V
3.168/3.135
V(min)
3.432/3.465
V(max)
78
%
Typical numbers are at 25°C and represent the most likely norm.
All limits specified 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 specified via correlation using standard Statistical Quality Control
(SQC) methods. All limits are used to calculate Average Outgoing Quality Level (AOQL).
External components such as the catch diode, inductor, input and output capacitors, and voltage programming resistors can affect
switching regulator system performance. When the LM2595 is used as shown in the Figure 21 test circuit, system performance will be
as shown in system parameters of Electrical Characteristics section.
LM2595-5.0 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
LM2595-5.0
Typ
Limit
(1)
SYSTEM PARAMETERS
VOUT
η
(3)
(3)
(2)
Test Circuit Figure 21
7V ≤ VIN ≤ 40V, 0.1A ≤ ILOAD ≤ 1A
Output Voltage
Efficiency
(1)
(2)
Units
(Limits)
VIN = 12V, ILOAD = 1A
5.0
V
4.800/4.750
V(min)
5.200/5.250
V(max)
82
%
Typical numbers are at 25°C and represent the most likely norm.
All limits specified 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 specified via correlation using standard Statistical Quality Control
(SQC) methods. All limits are used to calculate Average Outgoing Quality Level (AOQL).
External components such as the catch diode, inductor, input and output capacitors, and voltage programming resistors can affect
switching regulator system performance. When the LM2595 is used as shown in the Figure 21 test circuit, system performance will be
as shown in system parameters of Electrical Characteristics section.
LM2595-12 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
LM2595-12
Typ
(1)
SYSTEM PARAMETERS
VOUT
(1)
(2)
(3)
(3)
Output Voltage
Limit
Units
(Limits)
(2)
Test Circuit Figure 21
15V ≤ VIN ≤ 40V, 0.1A ≤ ILOAD ≤ 1A
12.0
V
11.52/11.40
V(min)
12.48/12.60
V(max)
Typical numbers are at 25°C and represent the most likely norm.
All limits specified 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 specified via correlation using standard Statistical Quality Control
(SQC) methods. All limits are used to calculate Average Outgoing Quality Level (AOQL).
External components such as the catch diode, inductor, input and output capacitors, and voltage programming resistors can affect
switching regulator system performance. When the LM2595 is used as shown in the Figure 21 test circuit, system performance will be
as shown in system parameters of Electrical Characteristics section.
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LM2595-12 Electrical Characteristics (continued)
Specifications with standard type face are for TJ = 25°C, and those with boldface type apply over full Operating
Temperature Range.
Symbol
Parameter
Conditions
LM2595-12
Typ
(1)
η
Efficiency
VIN = 25V, ILOAD = 1A
Units
(Limits)
Limit
(2)
90
%
LM2595-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
LM2595-ADJ
Typ
Limit
(1)
SYSTEM PARAMETERS
VFB
(3)
(2)
Test Circuit Figure 21
Feedback Voltage
4.5V ≤ VIN ≤ 40V, 0.1A ≤ ILOAD ≤ 1A
1.230
V
VOUT programmed for 3V. Circuit of Figure 21
η
(1)
(2)
(3)
Units
(Limits)
Efficiency
VIN = 12V, VOUT = 3V, ILOAD = 1A
1.193/1.180
V(min)
1.267/1.280
V(max)
78
%
Typical numbers are at 25°C and represent the most likely norm.
All limits specified 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 specified via correlation using standard Statistical Quality Control
(SQC) methods. All limits are used to calculate Average Outgoing Quality Level (AOQL).
External components such as the catch diode, inductor, input and output capacitors, and voltage programming resistors can affect
switching regulator system performance. When the LM2595 is used as shown in the Figure 21 test circuit, system performance will be
as shown in system parameters of Electrical Characteristics section.
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, VIN = 12V for the 3.3V, 5V, and Adjustable version and VIN = 24V for the
12V version. ILOAD = 200 mA.
Symbol
Parameter
Conditions
LM2595-XX
Typ
(1)
Limit
Units
(Limits)
(2)
DEVICE PARAMETERS
Ib
Feedback Bias Current
Adjustable Version Only,VFB = 1.3V
fO
Oscillator Frequency
See
VSAT
DC
Saturation Voltage
Max Duty Cycle (ON)
Min Duty Cycle (OFF)
(1)
(2)
(3)
(4)
(5)
(6)
4
(3)
IOUT = 1A
10
nA
50/100
nA (max)
127/110
kHz(min)
173/173
kHz(max)
1.2/1.3
V(max)
150
(4) (5)
kHz
1
See
(5)
100
See
(6)
0
V
%
Typical numbers are at 25°C and represent the most likely norm.
All limits specified 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 specified via correlation using standard Statistical Quality Control
(SQC) methods. All limits are used to calculate Average Outgoing Quality Level (AOQL).
The switching frequency is reduced when the second stage current limit is activated. The amount of reduction is determined by the
severity of current overload.
No diode, inductor or capacitor connected to output pin.
Feedback pin removed from output and connected to 0V to force the output transistor switch ON.
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.
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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
Temperature Range. Unless otherwise specified, VIN = 12V for the 3.3V, 5V, and Adjustable version and VIN = 24V for the
12V version. ILOAD = 200 mA.
Symbol
Parameter
Conditions
LM2595-XX
Typ
(1)
ICL
IL
Current Limit
Output Leakage Current
Peak Current
Output = 0V
(4) (5)
(4) (6)
and
(7)
(2)
Quiescent Current
See
ISTBY
Standby Quiescent
ON/OFF pin = 5V (OFF)
A
1.2/1.15
A(min)
2.4/2.6
A(max)
50
μA(max)
15
mA(max)
2
(6)
IQ
mA
5
(7)
mA
10
mA(max)
200/250
μA(max)
μA
85
Current
Thermal Resistance
Units
(Limits)
1.5
Output = −1V
θJC
Limit
2
°C/W
θJA
TO-220 or TO-263 Package, Junction to Case
TO-220 Package, Junction to Ambient
(8)
50
°C/W
θJA
TO-263 Package, Junction to Ambient
(9)
50
°C/W
θJA
TO-263 Package, Junction to Ambient
(10)
30
°C/W
θJA
TO-263 Package, Junction to Ambient
(11)
20
°C/W
1.3
V
ON/OFF CONTROL Test Circuit Figure 21
ON /OFF Pin Logic Input
VIH
Threshold Voltage
VIL
IH
IL
ON/OFF Pin
Input Current
Low (Regulator ON)
0.6
V(max)
High (Regulator OFF)
2.0
V(min)
VLOGIC = 2.5V (Regulator OFF)
5
VLOGIC = 0.5V (Regulator ON)
0.02
μA
15
μA(max)
5
μA(max)
μA
(7)
(8)
VIN = 40V.
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 in2.
(9) Junction to ambient thermal resistance with the TO-263 package tab soldered to a single printed circuit board with 0.5 in2 of (1 oz.)
copper area.
(10) Junction to ambient thermal resistance with the TO-263 package tab soldered to a single sided printed circuit board with 2.5 in2 of (1
oz.) copper area.
(11) Junction to ambient thermal resistance with the TO-263 package tab soldered to a double sided printed circuit board with 3 in2 of (1 oz.)
copper area on the LM2595S side of the board, and approximately 16 in2 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® version 4.3 software.
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Typical Performance Characteristics
(Circuit of Figure 21)
6
Normalized
Output Voltage
Line Regulation
Figure 4.
Figure 5.
Efficiency
Switch Saturation
Voltage
Figure 6.
Figure 7.
Switch Current Limit
Dropout Voltage
Figure 8.
Figure 9.
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Typical Performance Characteristics (continued)
(Circuit of Figure 21)
Operating
Quiescent Current
Shutdown
Quiescent Current
Figure 10.
Figure 11.
Minimum Operating
Supply Voltage
ON /OFF Threshold
Voltage
Figure 12.
Figure 13.
ON /OFF Pin
Current (Sinking)
Switching Frequency
Figure 14.
Figure 15.
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Typical Performance Characteristics (continued)
(Circuit of Figure 21)
Continuous Mode Switching Waveforms
VIN = 20V, VOUT = 5V, ILOAD = 1A
L = 68 μH, COUT = 120 μF, COUT ESR = 100 mΩ
Feedback Pin
Bias Current
Discontinuous Mode Switching Waveforms
VIN = 20V, VOUT = 5V, ILOAD = 600 mA
L = 22 μH, COUT = 220 μF, COUT ESR = 50 mΩ
8
B
1A
0.5A
0A
C
50 mV
AC/
div.
A: Output Pin Voltage, 10V/div.
B: Inductor Current 0.5A/div.
C: Output Ripple Voltage, 50 mV/div.
Horizontal Time Base: 2 µs/div.
Figure 17.
Figure 16.
A: Output Pin Voltage, 10V/div.
B: Inductor Current 0.5A/div.
C: Output Ripple Voltage, 50 mV/div.
Horizontal Time Base: 2 µs/div.
Figure 18.
A
20V
10V
0V
Load Transient Response for Continuous Mode
VIN = 20V, VOUT = 5V, ILOAD = 250 mA to 750 mA
L = 68 μH, COUT = 120 μF, COUT ESR = 100 mΩ
A: Output Voltage, 100 mV/div. (AC)
B: 250 mA to 750 mA Load Pulse
Horizontal Time Base: 100 µs/div.
Figure 19.
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Typical Performance Characteristics (continued)
(Circuit of Figure 21)
Load Transient Response for Discontinuous Mode
VIN = 20V, VOUT = 5V, ILOAD = 250 mA to 750 mA
L = 22 μH, COUT = 220 μF, COUT ESR = 50 mΩ
A
100 mV
AC/div.
B
1A
0.5A
0A
A: Output Voltage, 100 mV/div. (AC)
B: 250 mA to 750 mA Load Pulse
Horizontal Time Base: 200 µs/div.
Figure 20.
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Test Circuit and Layout Guidelines
Fixed Output Voltage Versions
CIN—120 μF, 50V, Aluminum Electrolytic Nichicon “PL Series”
COUT—120 μF, 25V Aluminum Electrolytic, Nichicon “PL Series”
D1—3A, 40V Schottky Rectifier, 1N5822
L1—100 μH, L29
Adjustable Output Voltage Versions
CIN—120 μF, 50V, Aluminum Electrolytic Nichicon “PL Series”
COUT—120 μF, 25V Aluminum Electrolytic, Nichicon “PL Series”
D1—3A, 40V Schottky Rectifier, 1N5822
L1—100 μH, L29
R1—1 kΩ, 1%
CFF—See Application Information Section
Figure 21. Standard Test Circuits and Layout Guides
Standard Test Circuits and Layout Guides
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.
10
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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 COUT 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 Information section for more information.)
Table 1. LM2595 Series Buck Regulator Design Procedure (Fixed Output)
PROCEDURE (Fixed Output Voltage Version)
EXAMPLE (Fixed Output Voltage Version)
Given:
VOUT = Regulated Output Voltage (3.3V, 5V or 12V)
VIN(max) = Maximum DC Input Voltage
ILOAD(max) = Maximum Load Current
Given:
VOUT = 5V
VIN(max) = 12V
ILOAD(max) = 1A
1. Inductor Selection (L1)
A. Select the correct inductor value selection guide from Figure 22 ,
Figure 23, or Figure 24. (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 Table 5.
1. Inductor Selection (L1)
A. Use the inductor selection guide for the 5V version shown in
Figure 23.
B. From the inductor value selection guide shown in Figure 23, the
inductance region intersected by the 12V horizontal line and the 1A
vertical line is 68 μH, and the inductor code is L30.
C. The inductance value required is 68 μH. From the table in
Table 5, go to the L30 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 (COUT)
A. In the majority of applications, low ESR (Equivalent Series
Resistance) electrolytic capacitors between 47 μF and 330 μF and
low ESR solid tantalum capacitors between 56 μF and 270 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 330 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 Table 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 4.2 or later.
2. Output Capacitor Selection (COUT)
A. See section on output capacitors in Application Information
section.
B. From the quick design component selection table shown in
Table 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 1A 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.
220 μF 25V Panasonic HFQ Series
220 μF 25V Nichicon PL Series
C. For a 5V output, a capacitor voltage rating at least 7.5V or more
is needed. But, in this example, even a low ESR, switching grade,
220 μF 10V aluminum electrolytic capacitor would exhibit
approximately 225 mΩ of ESR (see the curve in Figure 27 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 voltage rating (lower ESR)
should be selected. A 16V or 25V capacitor will reduce the ripple
voltage by approximately half.
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Table 1. LM2595 Series Buck Regulator Design Procedure (Fixed Output) (continued)
PROCEDURE (Fixed Output Voltage Version)
EXAMPLE (Fixed Output Voltage Version)
3. Catch Diode Selection (D1)
A. The catch diode current rating must be at least 1.3 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 LM2595. 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.
C. This diode must be fast (short reverse recovery time) and must be
located close to the LM2595 using short leads and short printed
circuit traces. Because of their fast switching speed and low forward
voltage drop, Schottky diodes provide the best performance and
efficiency, and should be the first choice, especially in low output
voltage applications. Ultra-fast recovery, or High-Efficiency rectifiers
also provide good results. Ultra-fast recovery diodes typically have
reverse recovery times of 50 ns or less. Rectifiers such as the
1N5400 series are much too slow and should not be used.
3. Catch Diode Selection (D1)
A. Refer to the table shown in Table 8 In this example, a 3A, 20V,
1N5820 Schottky diode will provide the best performance, and will
not be overstressed even for a shorted output.
4. Input Capacitor (CIN)
A low ESR aluminum or tantalum bypass capacitor is needed
between the input pin and ground pin to prevent large voltage
transients from appearing at the input. This capacitor should be
located close to the IC using short leads. In addition, the RMS
current rating of the input capacitor should be selected to be at least
½ the DC load current. The capacitor manufacturers data sheet must
be checked to assure that this current rating is not exceeded. The
curve shown in Figure 26 shows typical RMS current ratings for
several different aluminum electrolytic capacitor values.
For an aluminum electrolytic, the capacitor voltage rating should be
approximately 1.5 times the maximum input voltage. Caution must
be exercised if solid tantalum capacitors are used (see Application
Information on input capacitor). The tantalum capacitor voltage rating
should be 2 times the maximum input voltage and it is recommended
that they be surge current tested by the manufacturer.
Use caution when using ceramic capacitors for input bypassing,
because it may cause severe ringing at the VIN pin.
For additional information, see section on input capacitors in
Application Information section.
4. Input Capacitor (CIN)
The important parameters for the Input capacitor are the input
voltage rating and the RMS current rating. With a nominal input
voltage of 12V, an aluminum electrolytic capacitor with a voltage
rating greater than 18V (1.5 × VIN) would be needed. The next
higher capacitor voltage rating is 25V.
The RMS current rating requirement for the input capacitor in a buck
regulator is approximately ½ the DC load current. In this example,
with a 1A load, a capacitor with a RMS current rating of at least 500
mA is needed. The curves shown in Figure 26 can be used to select
an appropriate input capacitor. From the curves, locate the 25V line
and note which capacitor values have RMS current ratings greater
than 500 mA. Either a 180 μF or 220 μF, 25V capacitor could be
used.
For a through hole design, a 220 μF/25V electrolytic capacitor
(Panasonic HFQ series or Nichicon PL series or equivalent) would
be adequate. other types or other manufacturers capacitors can be
used provided the RMS ripple current ratings are adequate.
For surface mount designs, solid tantalum capacitors can be used,
but caution must be exercised with regard to the capacitor surge
current rating (see Application Information on input capacitors in this
data sheet). The TPS series available from AVX, and the 593D
series from Sprague are both surge current tested.
Table 2. LM2595 Fixed Voltage Quick Design Component Selection Table
Conditions
Inductor
Output Capacitor
Through Hole Electrolytic
Surface Mount Tantalum
Output
Load
Max Input
Inductance
Inductor
Panasonic
Nichicon
AVX TPS
Sprague
Voltage
Current
Voltage
(μH)
(#)
HFQ Series
PL Series
Series
595D Series
(V)
(A)
(V)
(μF/V)
(μF/V)
(μF/V)
(μF/V)
5
22
L24
330/16
330/16
220/10
330/10
7
33
L23
270/25
270/25
220/10
270/10
10
47
L31
220/25
220/35
220/10
220/10
40
68
L30
180/35
220/35
220/10
180/10
6
47
L13
220/25
220/16
220/10
220/10
10
68
L21
150/35
150/25
100/16
150/16
40
100
L20
150/35
82/35
100/16
100/20
1
3.3
0.5
12
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Table 2. LM2595 Fixed Voltage Quick Design Component Selection Table (continued)
Conditions
Inductor
Output Capacitor
Through Hole Electrolytic
Surface Mount Tantalum
Output
Load
Max Input
Inductance
Inductor
Panasonic
Nichicon
AVX TPS
Sprague
Voltage
Current
Voltage
(μH)
(#)
HFQ Series
PL Series
Series
595D Series
(V)
(A)
(V)
(μF/V)
(μF/V)
(μF/V)
(μF/V)
1
5
0.5
1
12
0.5
8
33
L28
330/16
330/16
220/10
270/10
10
47
L31
220/25
220/25
220/10
220/10
15
68
L30
180/35
180/35
220/10
150/16
40
100
L29
180/35
120/35
100/16
120/16
9
68
L21
180/16
180/16
220/10
150/16
20
150
L19
120/25
1200/25
100/16
100/20
40
150
L19
100/25
100/25
68/20
68/25
15
47
L31
220/25
220/25
68/20
120/20
18
68
L30
180/35
120/25
68/20
120/20
30
150
L36
82/25
82/25
68/20
100/20
40
220
L35
82/25
82/25
68/20
68/25
15
68
L21
180/25
180/25
68/20
120/20
20
150
L19
82/25
82/25
68/20
100/20
40
330
L26
56/25
56/25
68/20
68/25
Table 3. LM2595 Series Buck Regulator Design Procedure (Adjustable Output)
PROCEDURE (Adjustable Output Voltage Version)
EXAMPLE (Adjustable Output Voltage Version)
Given:
VOUT = Regulated Output Voltage
VIN(max) = Maximum Input Voltage
ILOAD(max) = Maximum Load Current
F = Switching Frequency (Fixed at a nominal 150 kHz).
Given:
VOUT = 20V
VIN(max) = 28V
ILOAD(max) = 1A
F = Switching Frequency (Fixed at a nominal 150 kHz).
1. Programming Output Voltage (Selecting R1 and R2, as shown in 1. Programming Output Voltage (Selecting R1 and R2, as shown in
Figure 21)
Figure 21)
Use the following formula to select the appropriate resistor values.
Select R1 to be 1 kΩ, 1%. Solve for R2.
(1)
(3)
Select a value for R1 between 240Ω and 1.5 kΩ. The lower resistor R2 = 1k (16.26 − 1) = 15.26k, closest 1% value is 15.4 kΩ.
values minimize noise pickup in the sensitive feedback pin. (For the R = 15.4 kΩ.
lowest temperature coefficient and the best stability with time, use 2
1% metal film resistors.)
(2)
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Table 3. LM2595 Series Buck Regulator Design Procedure (Adjustable Output) (continued)
PROCEDURE (Adjustable Output Voltage Version)
EXAMPLE (Adjustable Output Voltage Version)
2. Inductor Selection (L1)
2. Inductor Selection (L1)
A. Calculate the inductor Volt • microsecond constant E • T (V • μs), A. Calculate the inductor Volt • microsecond constant (E • T),
from the following formula:
(4)
where VSAT = internal switch saturation voltage = 1V
and VD = diode forward voltage drop = 0.5V
B. Use the E • T value from the previous formula and match it with
the E • T number on the vertical axis of the Inductor Value Selection
Guide shown in Figure 25.
C. on the horizontal axis, select the maximum load current.
D. Identify the inductance region intersected by the E • T value and
the Maximum Load Current value. Each region is identified by an
inductance value and an inductor code (LXX).
E. Select an appropriate inductor from the four manufacturer's part
numbers listed in Table 5.
(5)
B. E • T = 34.8 (V • μs)
C. ILOAD(max) = 1A
D. From the inductor value selection guide shown in Figure 25, the
inductance region intersected by the 35 (V • μs) horizontal line and
the 1A vertical line is 100 μH, and the inductor code is L29.
E. From the table in Table 5, locate line L29, and select an inductor
part number from the list of manufacturers part numbers.
3. Output Capacitor Selection (COUT)
A. In the majority of applications, low ESR electrolytic or solid
tantalum capacitors between 47 μF and 330 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 330 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 table shown in Table 4. This table contains different output
voltages, and lists various output capacitors that will provide the best
design solutions.
C. The capacitor voltage rating 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 needed for low output
ripple voltage.
3. Output Capacitor SeIection (COUT)
A. See section on COUT in Application Information section.
B. From the quick design table shown in Table 4, locate the output
voltage column. From that column, locate the output voltage closest
to the output voltage in your application. In this example, select the
24V line. Under the output capacitor section, select a capacitor from
the list of through hole electrolytic or surface mount tantalum types
from four different capacitor manufacturers. It is recommended that
both the manufacturers and the manufacturers series that are listed
in the table be used.
In this example, through hole aluminum electrolytic capacitors from
several different manufacturers are available.
82 μF, 35V Panasonic HFQ Series
82 μF, 35V Nichicon PL Series
C. For a 20V output, a capacitor rating of at least 30V or more is
needed. In this example, either a 35V or 50V capacitor would work.
A 35V rating was chosen, although a 50V rating could also be used
if a lower output ripple voltage is needed.
Other manufacturers or other types of capacitors may also be used,
provided the capacitor specifications (especially the 100 kHz ESR)
closely match the types listed in the table. Refer to the capacitor
manufacturers data sheet for this information.
4. Feedforward Capacitor (CFF) (See Figure 21)
For output voltages greater than approximately 10V, an additional
capacitor is required. The compensation capacitor is typically
between 50 pF and 10 nF, and is wired in parallel with the output
voltage setting resistor, R2. It provides additional stability for high
output voltages, low input-output voltages, and/or very low ESR
output capacitors, such as solid tantalum capacitors.
4. Feedforward Capacitor (CFF)
The table shown in Table 4 contains feed forward capacitor values
for various output voltages. In this example, a 1 nF capacitor is
needed.
(6)
This capacitor type can be ceramic, plastic, silver mica, etc.
(Because of the unstable characteristics of ceramic capacitors made
with Z5U material, they are not recommended.)
14
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Table 3. LM2595 Series Buck Regulator Design Procedure (Adjustable Output) (continued)
PROCEDURE (Adjustable Output Voltage Version)
EXAMPLE (Adjustable Output Voltage Version)
5. Catch Diode Selection (D1)
A. The catch diode current rating must be at least 1.3 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 LM2595. 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.
C. This diode must be fast (short reverse recovery time) and must be
located close to the LM2595 using short leads and short printed
circuit traces. Because of their fast switching speed and low forward
voltage drop, Schottky diodes provide the best performance and
efficiency, and should be the first choice, especially in low output
voltage applications. Ultra-fast recovery, or High-Efficiency rectifiers
are also a good choice, but some types with an abrupt turn-off
characteristic may cause instability or EMl problems. Ultra-fast
recovery diodes typically have reverse recovery times of 50 ns or
less. Rectifiers such as the 1N4001 series are much too slow and
should not be used.
5. Catch Diode Selection (D1)
A. Refer to the table shown in Table 8
Schottky diodes provide the best performance, and in this example a
3A, 40V, 1N5822 Schottky diode would be a good choice.
The 3A diode rating is more than adequate and will not be
overstressed even for a shorted output.
6. Input Capacitor (CIN)
A low ESR aluminum or tantalum bypass capacitor is needed
between the input pin and ground to prevent large voltage transients
from appearing at the input. In addition, the RMS current rating of
the input capacitor should be selected to be at least ½ the DC load
current. The capacitor manufacturers data sheet must be checked to
assure that this current rating is not exceeded. The curve shown in
Figure 26 shows typical RMS current ratings for several different
aluminum electrolytic capacitor values.
This capacitor should be located close to the IC using short leads
and the voltage rating should be approximately 1.5 times the
maximum input voltage.
If solid tantalum input capacitors are used, it is recomended that they
be surge current tested by the manufacturer.
se caution when using a high dielectric constant ceramic capacitor
for input bypassing, because it may cause severe ringing at the VIN
pin.
For additional information, see section on input capacitors in
Application Information section.
6. Input Capacitor (CIN)
The important parameters for the Input capacitor are the input
voltage rating and the RMS current rating. With a nominal input
voltage of 28V, an aluminum electrolytic aluminum electrolytic
capacitor with a voltage rating greater than 42V (1.5 × VIN) would be
needed. Since the the next higher capacitor voltage rating is 50V, a
50V capacitor should be used. The capacitor voltage rating of (1.5 ×
VIN) is a conservative guideline, and can be modified somewhat if
desired.
The RMS current rating requirement for the input capacitor of a buck
regulator is approximately ½ the DC load current. In this example,
with a 1A load, a capacitor with a RMS current rating of at least 500
mA is needed.
The curves shown in Figure 26 can be used to select an appropriate
input capacitor. From the curves, locate the 50V line and note which
capacitor values have RMS current ratings greater than 500 mA.
Either a 100 μF or 120 μF, 50V capacitor could be used.
For a through hole design, a 120 μF/50V electrolytic capacitor
(Panasonic HFQ series or Nichicon PL series or equivalent) would
be adequate. Other types or other manufacturers capacitors can be
used provided the RMS ripple current ratings are adequate.
For surface mount designs, solid tantalum capacitors can be used,
but caution must be exercised with regard to the capacitor surge
current rting (see Application Information or input capacitors in this
data sheet). The TPS series available from AVX, and the 593D
series from Sprague are both surge current tested.
To further simplify the buck regulator design procedure, Texas
Instruments is making available computer design software to be
used with the Simple Switcher line ot switching regulators.
Switchers Made Simple (version 4.2 or later) is available on a 3½″
diskette for IBM compatible computers.
Table 4. Output Capacitor and Feedforward Capacitor Selection Table
Output
Voltage
(V)
Through Hole Electrolytic Output Capacitor
Surface Mount Tantalum Output Capacitor
Panasonic
Nichicon PL
Feedforward
AVX TPS
Sprague
Feedforward
HFQ Series
Series
Capacitor
Series
595D Series
Capacitor
(μF/V)
(μF/V)
(μF/V)
(μF/V)
1.2
330/50
330/50
0
330/6.3
330/6.3
0
4
220/25
220/25
4.7 nF
220/10
220/10
4.7 nF
6
220/25
220/25
3.3 nF
220/10
220/10
3.3 nF
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Table 4. Output Capacitor and Feedforward Capacitor Selection Table (continued)
Output
Voltage
(V)
Through Hole Electrolytic Output Capacitor
Surface Mount Tantalum Output Capacitor
Panasonic
Nichicon PL
Feedforward
AVX TPS
Sprague
Feedforward
HFQ Series
Series
Capacitor
Series
595D Series
Capacitor
(μF/V)
(μF/V)
(μF/V)
(μF/V)
9
180/25
180/25
1.5 nF
100/16
180/16
1.5 nF
12
120/25
120/25
1.5 nF
68/20
120/20
1.5 nF
15
120/25
120/25
1.5 nF
68/20
100/20
1.5 nF
24
82/35
82/35
1 nF
33/25
33/35
220 pF
28
82/50
82/50
1 nF
10/35
33/35
220 pF
LM2595 Series Buck Regulator Design Procedure
INDUCTOR VALUE SELECTION GUIDES
(For Continuous Mode Operation)
16
Figure 22. LM2595-3.3
Figure 23. LM2595-5.0
Figure 24. LM2595-12
Figure 25. tLM2595-ADJ
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Table 5. Inductor Manufacturers Part Numbers
Inductance
(μH)
Current
(A)
Renco
L4
68
0.32
RL-1284-68-43
RL1500-68
PE-53804
PE-53804-S
DO1608-68
L5
47
0.37
RL-1284-47-43
RL1500-47
PE-53805
PE-53805-S
DO1608-473
L6
33
0.44
RL-1284-33-43
RL1500-33
PE-53806
PE-53806-S
DO1608-333
L9
220
0.32
RL-5470-3
RL1500-220
PE-53809
PE-53809-S
DO3308-224
L10
150
0.39
RL-5470-4
RL1500-150
PE-53810
PE-53810-S
DO3308-154
L11
100
0.48
RL-5470-5
RL1500-100
PE-53811
PE-53811-S
DO3308-104
L12
68
0.58
RL-5470-6
RL1500-68
PE-53812
PE-53812-S
DO3308-683
L13
47
0.70
RL-5470-7
RL1500-47
PE-53813
PE-53813-S
DO3308-473
L14
33
0.83
RL-1284-33-43
RL1500-33
PE-53814
PE-53814-S
DO3308-333
L15
22
0.99
RL-1284-22-43
RL1500-22
PE-53815
PE-53815-S
DO3308-223
L16
15
1.24
RL-1284-15-43
RL1500-15
PE-53816
PE-53816-S
DO3308-153
L17
330
0.42
RL-5471-1
RL1500-330
PE-53817
PE-53817-S
DO3316-334
L18
220
0.55
RL-5471-2
RL1500-220
PE-53818
PE-53818-S
DO3316-224
L19
150
0.66
RL-5471-3
RL1500-150
PE-53819
PE-53819-S
DO3316-154
L20
100
0.82
RL-5471-4
RL1500-100
PE-53820
PE-53820-S
DO3316-104
L21
68
0.99
RL-5471-5
RL1500-68
PE-53821
PE-53821-S
DO3316-683
L22
47
1.17
RL-5471-6
—
PE-53822
PE-53822-S
DO3316-473
L23
33
1.40
RL-5471-7
—
PE-53823
PE-53823-S
DO3316-333
L24
22
1.70
RL-1283-22-43
—
PE-53824
PE-53824-S
DO3316-223
L26
330
0.80
RL-5471-1
—
PE-53826
PE-53826-S
DO5022P-334
L27
220
1.00
RL-5471-2
—
PE-53827
PE-53827-S
DO5022P-224
L28
150
1.20
RL-5471-3
—
PE-53828
PE-53828-S
DO5022P-154
L29
100
1.47
RL-5471-4
—
PE-53829
PE-53829-S
DO5022P-104
L30
68
1.78
RL-5471-5
—
PE-53830
PE-53830-S
DO5022P-683
L35
47
2.15
RL-5473-1
—
PE-53935
PE-53935-S
—
Through Hole
Pulse Engineering
Surface Mount
Through
Hole
Surface Mount
Coilcraft
Surface Mount
Table 6. Inductor Manufacturers Phone Numbers
Coilcraft Inc.
Coilcraft Inc., Europe
Pulse Engineering Inc.
Phone
(800) 322-2645
FAX
(708) 639-1469
Phone
+11 1236 730 595
FAX
+44 1236 730 627
Phone
(619) 674-8100
FAX
(619) 674-8262
Pulse Engineering Inc.,
Phone
+353 93 24 107
Europe
FAX
+353 93 24 459
Renco Electronics Inc.
Phone
(800) 645-5828
FAX
(516) 586-5562
Table 7. Capacitor Manufacturers Phone Numbers
Nichicon Corp.
Panasonic
AVX Corp.
Phone
(708) 843-7500
FAX
(708) 843-2798
Phone
(714) 373-7857
FAX
(714) 373-7102
Phone
(803) 448-9411
FAX
(803) 448-1943
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Table 7. Capacitor Manufacturers Phone Numbers (continued)
Sprague/Vishay
Phone
(207) 324-4140
FAX
(207) 324-7223
Table 8. Diode Selection Table
VR
1A Diodes
Surface Mount
Schottky
Ultra Fast
3A Diodes
Through Hole
Schottky
Recovery
SK12
20V
SK13
30V
MBRS130
All of
these
diodes
are
rated to
at least
50V.
1N5817
SR102
1N5818
SR103
Ultra Fast
Surface Mount
Schottky
Ultra Fast
Recovery
Recovery
All of
these
diodes
are
rated to
at least
50V.
All of
these
diodes
are
rated to
at least
50V.
SK32
SK33
11DQ03
Ultra Fast
Recovery
1N5820
SR302
MBR320
1N5821
MBR330
All of
these
diodes
are
rated to
at least
50V.
31DQ03
SK14
40V
Through Hole
Schottky
1N5822
MBRS140
1N5819
SK34
SR304
10BQ040
SR104
MBRS340
MBR340
10MQ040
MURS120
50V
MBRS160
10BF10
or
More
11DQ04
MUR120
30WQ04
MURS320
30WF10
31DQ04
MUR320
SR305
30WF10
SR105
SK35
10BQ050
MBR150
MBR360
MBR350
10MQ060
11DQ05
30WQ05
31DQ05
Block Diagram
18
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APPLICATION INFORMATION
PIN FUNCTIONS
+VIN
This is the positive input supply for the IC switching regulator. A suitable input bypass capacitor must be
present at this pin to minimize voltage transients and to supply the switching currents needed by the
regulator.
Ground Circuit ground.
Output Internal switch. The voltage at this pin switches between (+VIN − VSAT) and approximately −0.5V, with a
duty cycle of approximately VOUT/VIN. To minimize coupling to sensitive circuitry, the PC board copper
area connected to this pin should be kept to a minimum.
Feedback Senses the regulated output voltage to complete the feedback loop.
ON/OFF Allows the switching regulator circuit to be shut down using logic level signals thus dropping the total
input supply current to approximately 85 μA. Pulling this pin below a threshold voltage of approximately
1.3V turns the regulator on, and pulling this pin above 1.3V (up to a maximum of 25V) shuts the regulator
down. If this shutdown feature is not needed, the ON/OFF pin can be wired to the ground pin or it can be
left open, in either case the regulator will be in the ON condition.
EXTERNAL COMPONENTS INPUT CAPACITOR
CIN —A low ESR aluminum or tantalum bypass capacitor is needed between the input pin and ground pin. It
must be located near the regulator using short leads. This capacitor prevents large voltage transients from
appearing at the input, and provides the instantaneous current needed each time the switch turns on.
The important parameters for the Input capacitor are the voltage rating and the RMS current rating. Because of
the relatively high RMS currents flowing in a buck regulator's input capacitor, this capacitor should be chosen for
its RMS current rating rather than its capacitance or voltage ratings, although the capacitance value and voltage
rating are directly related to the RMS current rating.
The RMS current rating of a capacitor could be viewed as a capacitor's power rating. The RMS current flowing
through the capacitors internal ESR produces power which causes the internal temperature of the capacitor to
rise. The RMS current rating of a capacitor is determined by the amount of current required to raise the internal
temperature approximately 10°C above an ambient temperature of 105°C. The ability of the capacitor to dissipate
this heat to the surrounding air will determine the amount of current the capacitor can safely sustain. Capacitors
that are physically large and have a large surface area will typically have higher RMS current ratings. For a given
capacitor value, a higher voltage electrolytic capacitor will be physically larger than a lower voltage capacitor, and
thus be able to dissipate more heat to the surrounding air, and therefore will have a higher RMS current rating.
The consequences of operating an electrolytic capacitor above the RMS current rating is a shortened operating
life. The higher temperature speeds up the evaporation of the capacitor's electrolyte, resulting in eventual failure.
Selecting an input capacitor requires consulting the manufacturers data sheet for maximum allowable RMS ripple
current. For a maximum ambient temperature of 40°C, a general guideline would be to select a capacitor with a
ripple current rating of approximately 50% of the DC load current. For ambient temperatures up to 70°C, a
current rating of 75% of the DC load current would be a good choice for a conservative design. The capacitor
voltage rating must be at least 1.25 times greater than the maximum input voltage, and often a much higher
voltage capacitor is needed to satisfy the RMS current requirements.
A graph shown in Figure 26 shows the relationship between an electrolytic capacitor value, its voltage rating, and
the RMS current it is rated for. These curves were obtained from the Nichicon “PL” series of low ESR, high
reliability electrolytic capacitors designed for switching regulator applications. Other capacitor manufacturers offer
similar types of capacitors, but always check the capacitor data sheet.
“Standard” electrolytic capacitors typically have much higher ESR numbers, lower RMS current ratings and
typically have a shorter operating lifetime.
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Because of their small size and excellent performance, surface mount solid tantalum capacitors are often used
for input bypassing, but several precautions must be observed. A small percentage of solid tantalum capacitors
can short if the inrush current rating is exceeded. This can happen at turn on when the input voltage is suddenly
applied, and of course, higher input voltages produce higher inrush currents. Several capacitor manufacturers do
a 100% surge current testing on their products to minimize this potential problem. If high turn on currents are
expected, it may be necessary to limit this current by adding either some resistance or inductance before the
tantalum capacitor, or select a higher voltage capacitor. As with aluminum electrolytic capacitors, the RMS ripple
current rating must be sized to the load current.
FEEDFORWARD CAPACITOR
(Adjustable Output Voltage Version)
CFF -A Feedforward Capacitor CFF, shown across R2 in Figure 21 is used when the output voltage is greater than
10V or when COUT has a very low ESR. This capacitor adds lead compensation to the feedback loop and
increases the phase margin for better loop stability. For CFF selection, see the Design Procedure section.
Figure 26. RMS Current Ratings for Low ESR Electrolytic Capacitors (Typical)
OUTPUT CAPACITOR
COUT —An output capacitor is required to filter the output and provide regulator loop stability. Low impedance or
low ESR Electrolytic or solid tantalum capacitors designed for switching regulator applications must be used.
When selecting an output capacitor, the important capacitor parameters are; the 100 kHz Equivalent Series
Resistance (ESR), the RMS ripple current rating, voltage rating, and capacitance value. For the output capacitor,
the ESR value is the most important parameter.
The output capacitor requires an ESR value that has an upper and lower limit. For low output ripple voltage, a
low ESR value is needed. This value is determined by the maximum allowable output ripple voltage, typically 1%
to 2% of the output voltage. But if the selected capacitor's ESR is extremely low, there is a possibility of an
unstable feedback loop, resulting in an oscillation at the output. Using the capacitors listed in the tables, or
similar types, will provide design solutions under all conditions.
If very low output ripple voltage (less than 15 mV) is required, refer to the section on OUTPUT VOLTAGE
RIPPLE AND TRANSIENTS for a post ripple filter.
An aluminum electrolytic capacitor's ESR value is related to the capacitance value and its voltage rating. In most
cases, higher voltage electrolytic capacitors have lower ESR values (see Figure 27). Often, capacitors with much
higher voltage ratings may be needed to provide the low ESR values required for low output ripple voltage.
The output capacitor for many different switcher designs often can be satisfied with only three or four different
capacitor values and several different voltage ratings. See the quick design component selection tables in
Table 2 and Table 4 for typical capacitor values, voltage ratings, and manufacturers capacitor types.
Electrolytic capacitors are not recommended for temperatures below −25°C. The ESR rises dramatically at cold
temperatures and typically rises 3X @ −25°C and as much as 10X at −40°C. See curve shown in Figure 28.
20
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Solid tantalum capacitors have a much better ESR spec for cold temperatures and are recommended for
temperatures below −25°C.
Figure 27. Capacitor ESR vs Capacitor Voltage Rating (Typical Low ESR Electrolytic Capacitor)
CATCH DIODE
Buck regulators require a diode to provide a return path for the inductor current when the switch turns off. This
must be a fast diode and must be located close to the LM2595 using short leads and short printed circuit traces.
Because of their very fast switching speed and low forward voltage drop, Schottky diodes provide the best
performance, especially in low output voltage applications (5V and lower). Ultra-fast recovery, or High-Efficiency
rectifiers are also a good choice, but some types with an abrupt turnoff characteristic may cause instability or
EMI problems. Ultra-fast recovery diodes typically have reverse recovery times of 50 ns or less. Rectifiers such
as the 1N5400 series are much too slow and should not be used.
Figure 28. Capacitor ESR Change vs Temperature
INDUCTOR SELECTION
All switching regulators have two basic modes of operation; continuous and discontinuous. The difference
between the two types relates to the inductor current, whether it is flowing continuously, or if it drops to zero for a
period of time in the normal switching cycle. Each mode has distinctively different operating characteristics,
which can affect the regulators performance and requirements. Most switcher designs will operate in the
discontinuous mode when the load current is low.
The LM2595 (or any of the Simple Switcher family) can be used for both continuous or discontinuous modes of
operation.
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In many cases the preferred mode of operation is the continuous mode. It offers greater output power, lower
peak switch, inductor and diode currents, and can have lower output ripple voltage. But it does require larger
inductor values to keep the inductor current flowing continuously, especially at low output load currents and/or
high input voltages.
To simplify the inductor selection process, an inductor selection guide (nomograph) was designed (see Figure 22
through Figure 25). This guide assumes that the regulator is operating in the continuous mode, and selects an
inductor that will allow a peak-to-peak inductor ripple current to be a certain percentage of the maximum design
load current. This peak-to-peak inductor ripple current percentage is not fixed, but is allowed to change as
different design load currents are selected. (See Figure 29.)
Figure 29. (ΔIIND) Peak-to-Peak
Inductor Ripple Current (as a Percentage
of the Load Current) vs Load Current
By allowing the percentage of inductor ripple current to increase for low load currents, the inductor value and size
can be kept relatively low.
When operating in the continuous mode, the inductor current waveform ranges from a triangular to a sawtooth
type of waveform (depending on the input voltage), with the average value of this current waveform equal to the
DC output load current.
Inductors are available in different styles such as pot core, toroid, E-core, bobbin core, etc., as well as different
core materials, such as ferrites and powdered iron. The least expensive, the bobbin, rod or stick core, consists of
wire wound on a ferrite bobbin. This type of construction makes for an inexpensive inductor, but since the
magnetic flux is not completely contained within the core, it generates more Electro-Magnetic Interference (EMl).
This magnetic flux can induce voltages into nearby printed circuit traces, thus causing problems with both the
switching regulator operation and nearby sensitive circuitry, and can give incorrect scope readings because of
induced voltages in the scope probe. Also see section on OPEN CORE INDUCTORS.
When multiple switching regulators are located on the same PC board, open core magnetics can cause
interference between two or more of the regulator circuits, especially at high currents. A toroid or E-core inductor
(closed magnetic structure) should be used in these situations.
The inductors listed in the selection chart include ferrite E-core construction for Schott, ferrite bobbin core for
Renco and Coilcraft, and powdered iron toroid for Pulse Engineering.
Exceeding an inductor's maximum current rating may cause the inductor to overheat because of the copper wire
losses, or the core may saturate. If the inductor begins to saturate, the inductance decreases rapidly and the
inductor begins to look mainly resistive (the DC resistance of the winding). This can cause the switch current to
rise very rapidly and force the switch into a cycle-by-cycle current limit, thus reducing the DC output load current.
This can also result in overheating of the inductor and/or the LM2595. Different inductor types have different
saturation characteristics, and this should be kept in mind when selecting an inductor.
The inductor manufacturer's data sheets include current and energy limits to avoid inductor saturation.
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DISCONTINUOUS MODE OPERATION
The selection guide chooses inductor values suitable for continuous mode operation, but for low current
applications and/or high input voltages, a discontinuous mode design may be a better choice. It would use an
inductor that would be physically smaller, and would need only one half to one third the inductance value needed
for a continuous mode design. The peak switch and inductor currents will be higher in a discontinuous design,
but at these low load currents (400 mA and below), the maximum switch current will still be less than the switch
current limit.
Discontinuous operation can have voltage waveforms that are considerable different than a continuous design.
The output pin (switch) waveform can have some damped sinusoidal ringing present. (See Typical Performance
Characteristics photo titled Discontinuous Mode Switching Waveforms) This ringing is normal for discontinuous
operation, and is not caused by feedback loop instabilities. In discontinuous operation, there is a period of time
where neither the switch or the diode are conducting, and the inductor current has dropped to zero. During this
time, a small amount of energy can circulate between the inductor and the switch/diode parasitic capacitance
causing this characteristic ringing. Normally this ringing is not a problem, unless the amplitude becomes great
enough to exceed the input voltage, and even then, there is very little energy present to cause damage.
Different inductor types and/or core materials produce different amounts of this characteristic ringing. Ferrite core
inductors have very little core loss and therefore produce the most ringing. The higher core loss of powdered iron
inductors produce less ringing. If desired, a series RC could be placed in parallel with the inductor to dampen the
ringing. The computer aided design software Switchers Made Simple (version 4.3) will provide all component
values for continuous and discontinuous modes of operation.
Before
Ripple
Filter
5 mV/div
Alter
Ripple
Filter
2 µsec/div
Figure 30. Post Ripple Filter Waveform
OUTPUT VOLTAGE RIPPLE AND TRANSIENTS
The output voltage of a switching power supply operating in the continuous mode will contain a sawtooth ripple
voltage at the switcher frequency, and may also contain short voltage spikes at the peaks of the sawtooth
waveform.
The output ripple voltage is a function of the inductor sawtooth ripple current and the ESR of the output
capacitor. A typical output ripple voltage can range from approximately 0.5% to 3% of the output voltage. To
obtain low ripple voltage, the ESR of the output capacitor must be low, however, caution must be exercised when
using extremely low ESR capacitors because they can affect the loop stability, resulting in oscillation problems. If
very low output ripple voltage is needed (less than 20 mV), a post ripple filter is recommended. (See Figure 21.)
The inductance required is typically between 1 μH and 5 μH, with low DC resistance, to maintain good load
regulation. A low ESR output filter capacitor is also required to assure good dynamic load response and ripple
reduction. The ESR of this capacitor may be as low as desired, because it is out of the regulator feedback loop.
The photo shown in Figure 30 shows a typical output ripple voltage, with and without a post ripple filter.
When observing output ripple with a scope, it is essential that a short, low inductance scope probe ground
connection be used. Most scope probe manufacturers provide a special probe terminator which is soldered onto
the regulator board, preferable at the output capacitor. This provides a very short scope ground thus eliminating
the problems associated with the 3 inch ground lead normally provided with the probe, and provides a much
cleaner and more accurate picture of the ripple voltage waveform.
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The voltage spikes are caused by the fast switching action of the output switch and the diode, and the parasitic
inductance of the output filter capacitor, and its associated wiring. To minimize these voltage spikes, the output
capacitor should be designed for switching regulator applications, and the lead lengths must be kept very short.
Wiring inductance, stray capacitance, as well as the scope probe used to evaluate these transients, all contribute
to the amplitude of these spikes.
When a switching regulator 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 and output voltage,
the peak-to-peak amplitude of this inductor current waveform remains constant. As the load current increases or
decreases, the entire sawtooth current waveform also rises and falls. The average value (or the center) of this
current waveform is equal to the DC load current.
If the load current drops to a low enough level, the bottom of the sawtooth current waveform will reach zero, and
the switcher will smoothly change from a continuous to a discontinuous mode of operation. Most switcher
designs (irregardless how large the inductor value is) will be forced to run discontinuous if the output is lightly
loaded. This is a perfectly acceptable mode of operation.
Figure 31. Peak-to-Peak Inductor
Ripple Current vs Load Current
In a switching regulator design, knowing the value of the peak-to-peak inductor ripple current (ΔIIND) can be
useful for determining a number of other circuit parameters. Parameters such as, peak inductor or peak switch
current, minimum load current before the circuit becomes discontinuous, output ripple voltage and output
capacitor ESR can all be calculated from the peak-to-peak ΔIIND. When the inductor nomographs shown in
Figure 22 through Figure 25 are used to select an inductor value, the peak-to-peak inductor ripple current can
immediately be determined. The curve shown in Figure 31 shows the range of (ΔIIND) that can be expected for
different load currents. The curve also shows how the peak-to-peak inductor ripple current (ΔIIND) changes as
you go from the lower border to the upper border (for a given load current) within an inductance region. The
upper border represents a higher input voltage, while the lower border represents a lower input voltage (see
INDUCTOR SELECTION Guides).
These curves are only correct for continuous mode operation, and only if the inductor selection guides are used
to select the inductor value
Consider the following example:
VOUT = 5V, maximum load current of 800 mA
VIN = 12V, nominal, varying between 10V and 14V.
The selection guide in Figure 23 shows that the vertical line for a 0.8A load current, and the horizontal line for the
12V input voltage intersect approximately midway between the upper and lower borders of the 68 μH inductance
region. A 68 μH inductor will allow a peak-to-peak inductor current (ΔIIND) to flow that will be a percentage of the
maximum load current. Referring to Figure 31, follow the 0.8A line approximately midway into the inductance
region, and read the peak-to-peak inductor ripple current (ΔIIND) on the left hand axis (approximately 300 mA pp).
24
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As the input voltage increases to 14V, it approaches the upper border of the inductance region, and the inductor
ripple current increases. Referring to the curve in Figure 31, it can be seen that for a load current of 0.8A, the
peak-to-peak inductor ripple current (ΔIIND) is 300 mA with 12V in, and can range from 340 mA at the upper
border (14V in) to 225 mA at the lower border (10V in).
Once the ΔIIND value is known, the following formulas can be used to calculate additional information about the
switching regulator circuit.
1. Peak Inductor or peak switch current
2. Minimum load current before the circuit becomes discontinuous
3. Output Ripple Voltage = (ΔIIND)×(ESR of COUT)
= 0.30A×0.16Ω=48 mV p-p
4. ESR of COUT
OPEN CORE INDUCTORS
Another possible source of increased output ripple voltage or unstable operation is from an open core inductor.
Ferrite bobbin or stick inductors have magnetic lines of flux flowing through the air from one end of the bobbin to
the other end. These magnetic lines of flux will induce a voltage into any wire or PC board copper trace that
comes within the inductor's magnetic field. The strength of the magnetic field, the orientation and location of the
PC copper trace to the magnetic field, and the distance between the copper trace and the inductor, determine
the amount of voltage generated in the copper trace. Another way of looking at this inductive coupling is to
consider the PC board copper trace as one turn of a transformer (secondary) with the inductor winding as the
primary. Many millivolts can be generated in a copper trace located near an open core inductor which can cause
stability problems or high output ripple voltage problems.
If unstable operation is seen, and an open core inductor is used, it's possible that the location of the inductor with
respect to other PC traces may be the problem. To determine if this is the problem, temporarily raise the inductor
away from the board by several inches and then check circuit operation. If the circuit now operates correctly,
then the magnetic flux from the open core inductor is causing the problem. Substituting a closed core inductor
such as a torroid or E-core will correct the problem, or re-arranging the PC layout may be necessary. Magnetic
flux cutting the IC device ground trace, feedback trace, or the positive or negative traces of the output capacitor
should be minimized.
Sometimes, locating a trace directly beneath a bobbin inductor will provide good results, provided it is exactly in
the center of the inductor (because the induced voltages cancel themselves out), but if it is off center one
direction or the other, then problems could arise. If flux problems are present, even the direction of the inductor
winding can make a difference in some circuits.
This discussion on open core inductors is not to frighten the user, but to alert the user on what kind of problems
to watch out for when using them. Open core bobbin or “stick” inductors are an inexpensive, simple way of
making a compact efficient inductor, and they are used by the millions in many different applications.
THERMAL CONSIDERATIONS
The LM2595 is available in two packages, a 5-pin TO-220 (NDH) and a 5-pin surface mount TO-263 (KTT).
The TO-220 package can be used without a heat sink for ambient temperatures up to approximately 50°C
(depending on the output voltage and load current). The curves in Figure 32 show the LM2595T junction
temperature rises above ambient temperature for different input and output voltages. The data tor these curves
was taken with the LM2595T (TO-220 package) operating as a switching regutator in an ambient temperature of
25°C (still air). These temperature rise numbers are all approximate and there are many factors that can affect
these temperatures. Higher ambient temperatures require some heat sinking, either to the PC board or a small
external heat sink.
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The TO-263 surface mount package tab is designed to be soldered to the copper on a printed circuit board. The
copper and the board are the heat sink for this package and the other heat producing components, such as the
catch diode and inductor. The PC board copper area that the package is soldered to should be at least 0.4 in2,
and ideally should have 2 or more square inches of 2 oz. (0.0028 in) copper. Additional copper area improves
the thermal characteristics, but with copper areas greater than approximately 3 in2, only small improvements in
heat dissipation are realized. If further thermal improvements are needed, double sided or multilayer PC-board
with large copper areas are recommended.
The curves shown in Figure 33 show the LM2595S (TO-263 package) junction temperature rise above ambient
temperature with a 1A load for various input and output voltages. This data was taken with the circuit operating
as a buck switching regulator with all components mounted on a PC board to simulate the junction temperature
under actual operating conditions. This curve can be used for a quick check for the approximate junction
temperature for various conditions, but be aware that there are many factors that can affect the junction
temperature.
For the best thermal performance, wide copper traces and generous amounts of printed circuit board copper
should be used in the board layout. (One exception to this is the output (switch) pin, which should not have large
areas of copper.) Large areas of copper provide the best transfer of heat (lower thermal resistance) to the
surrounding air, and moving air lowers the thermal resistance even further.
Package thermal resistance and junction temperature rise numbers are all approximate, and there are many
factors that will affect these numbers. Some of these factors include board size, shape, thickness, position,
location, and even board temperature. Other factors are, trace width, total printed circuit copper area, copper
thickness, single- or double-sided, multilayer board and the amount of solder on the board. The effectiveness of
the PC board to dissipate heat also depends on the size, quantity and spacing of other components on the
board, as well as whether the surrounding air is still or moving. Furthermore, some of these components such as
the catch diode will add heat to the PC board and the heat can vary as the input voltage changes. For the
inductor, depending on the physical size, type of core material and the DC resistance, it could either act as a
heat sink taking heat away from the board, or it could add heat to the board.
Circuit Data for Temperature Rise Curve
TO-220 Package (NDH)
Capacitors
Through hole electrolytic
Inductor
Through hole, Schott, 68 μH
Diode
Through hole, 3A 40V, Schottky
PC board
3 square inches single sided 2 oz. copper (0.0028″)
Figure 32. Junction Temperature Rise, TO-220
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Circuit Data for Temperature Rise Curve
TO-263 Package (KTT)
Capacitors
Surface mount tantalum, molded “D” size
Inductor
Surface mount, Schott, 68 μH
Diode
Surface mount, 3A 40V, Schottky
PC board
3 square inches single sided 2 oz. copper (0.0028″)
Figure 33. Junction Temperature Rise, TO-263
Figure 34. Delayed Startup
Figure 35. Undervoltage Lockout for Buck Regulator
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DELAYED STARTUP
The circuit in Figure 34 uses the the ON /OFF pin to provide a time delay between the time the input voltage is
applied and the time the output voltage comes up (only the circuitry pertaining to the delayed start up is shown).
As the input voltage rises, the charging of capacitor C1 pulls the ON /OFF pin high, keeping the regulator off.
Once the input voltage reaches its final value and the capacitor stops charging, and resistor R2 pulls the ON
/OFF pin low, thus allowing the circuit to start switching. Resistor R1 is included to limit the maximum voltage
applied to the ON /OFF pin (maximum of 25V), reduces power supply noise sensitivity, and also limits the
capacitor, C1, discharge current. When high input ripple voltage exists, avoid long delay time, because this ripple
can be coupled into the ON /OFF pin and cause problems.
This delayed startup feature is useful in situations where the input power source is limited in the amount of
current it can deliver. It allows the input voltage to rise to a higher voltage before the regulator starts operating.
Buck regulators require less input current at higher input voltages.
UNDERVOLTAGE LOCKOUT
Some applications require the regulator to remain off until the input voltage reaches a predetermined voltage. An
undervoltage lockout feature applied to a buck regulator is shown in Figure 35, while Figure 36 and Figure 37
applies the same feature to an inverting circuit. The circuit in Figure 36 features a constant threshold voltage for
turn on and turn off (zener voltage plus approximately one volt). If hysteresis is needed, the circuit in Figure 37
has a turn ON voltage which is different than the turn OFF voltage. The amount of hysteresis is approximately
equal to the value of the output voltage. If zener voltages greater than 25V are used, an additional 47 kΩ resistor
is needed from the ON /OFF pin to the ground pin to stay within the 25V maximum limit of the ON /OFF pin.
INVERTING REGULATOR
The circuit in Figure 38 converts a positive input voltage to a negative output voltage with a common ground. The
circuit operates by bootstrapping the regulator's ground pin to the negative output voltage, then grounding the
feedback pin, the regulator senses the inverted output voltage and regulates it.
This circuit has an ON/OFF threshold of approximately 13V.
Figure 36. Undervoltage Lockout for Inverting Regulator
This example uses the LM2595-5.0 to generate a −5V output, but other output voltages are possible by selecting
other output voltage versions, including the adjustable version.
Since this regulator topology can produce an output voltage that is either greater than or less than the input
voltage, the maximum output current greatly depends on both the input and output voltage. The curve shown in
Figure 39 provides a guide as to the amount of output load current possible for the different input and output
voltage conditions.
The maximum voltage appearing across the regulator is the absolute sum of the input and output voltage, and
this must be limited to a maximum of 40V. For example, when converting +20V to −12V, the regulator would see
32V between the input pin and ground pin. The LM2595 has a maximum input voltage spec of 40V.
Additional diodes are required in this regulator configuration. Diode D1 is used to isolate input voltage ripple or
noise from coupling through the CIN capacitor to the output, under light or no load conditions. Also, this diode
isolation changes the topology to closley resemble a buck configuration thus providing good closed loop stability.
A Schottky diode is recommended for low input voltages, (because of its lower voltage drop) but for higher input
voltages, a fast recovery diode could be used.
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Without diode D3, when the input voltage is first applied, the charging current of CIN can pull the output positive
by several volts for a short period of time. Adding D3 prevents the output from going positive by more than a
diode voltage.
This circuit has hysteresis
Regulator starts switching at VIN = 13V
Regulator stops switching at VIN = 8V
Figure 37. Undervoltage Lockout with Hysteresis for Inverting Regulator
CIN: — 220 μF/25V Tant. Sprague 595D
120 μF/50V Elec. Panasonic HFQ
COUT: — 22 μF/20V Tant. Sprague 595D
120 μF/25V Elec. Panasonic HFQ
Figure 38. Inverting −5V Regulator with Delayed Startup
Figure 39. Inverting Regulator Typical Load Current
Because of differences in the operation of the inverting regulator, the standard design procedure is not used to
select the inductor value. In the majority of designs, a 68 μH, 1.5A inductor is the best choice. Capacitor
selection can also be narrowed down to just a few values. Using the values shown in Figure 38 will provide good
results in the majority of inverting designs.
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This type of inverting regulator can require relatively large amounts of input current when starting up, even with
light loads. Input currents as high as the LM2595 current limit (approx 1.5A) are needed for at least 2 ms or
more, until the output reaches its nominal output voltage. The actual time depends on the output voltage and the
size of the output capacitor. Input power sources that are current limited or sources that can not deliver these
currents without getting loaded down, may not work correctly. Because of the relatively high startup currents
required by the inverting topology, the delayed startup feature (C1, R1 and R2) shown in Figure 38 is
recommended. By delaying the regulator startup, the input capacitor is allowed to charge up to a higher voltage
before the switcher begins operating. A portion of the high input current needed for startup is now supplied by the
input capacitor (CIN). For severe start up conditions, the input capacitor can be made much larger than normal.
INVERTING REGULATOR SHUTDOWN METHODS
To use the ON /OFF pin in a standard buck configuration is simple, pull it below 1.3V (@25°C, referenced to
ground) to turn regulator ON, pull it above 1.3V to shut the regulator OFF. With the inverting configuration, some
level shifting is required, because the ground pin of the regulator is no longer at ground, but is now setting at the
negative output voltage level. Two different shutdown methods for inverting regulators are shown in Figure 40
and Figure 41.
Figure 40. Inverting Regulator Ground Referenced Shutdown
Figure 41. Inverting Regulator Ground Referenced Shutdown using Opto Device
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TYPICAL THROUGH HOLE PC BOARD LAYOUT, FIXED OUTPUT (1X SIZE)
CIN - 150 μF, 50V, Aluminium Electrolytic Nichicon, “PL series”
COUT - 120 μF, 25V Aluminium Electrolytic Nichicon, “PL series”
D1 - 3A, 40V Schottky Rectifier, 1N5822
L1 - 68 μH, L30, Schott, Through hole
TYPICAL THROUGH HOLE PC BOARD LAYOUT, ADJUSTABLE OUTPUT (1X SIZE)
CIN - 150 μF, 50V, Aluminium Electrolytic Nichicon, “PL series”
COUT - 120 μF, 25V Aluminium Electrolytic Nichicon, “PL series”
D1 - 3A, 40V Schottky Rectifier, 1N5822
L1 - 68 μH, L30, Schott, Through hole
R1 - 1 kΩ, 1%
R2 - Use formula in Design Procedure
CFF - See Table 4
Figure 42. PC Board Layout
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REVISION HISTORY
Changes from Revision A (April 2013) to Revision B
•
32
Page
Changed layout of National Data Sheet to TI format .......................................................................................................... 31
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PACKAGE OPTION ADDENDUM
www.ti.com
11-Apr-2013
PACKAGING INFORMATION
Orderable Device
Status
(1)
Package Type Package Pins Package
Drawing
Qty
Eco Plan
Lead/Ball Finish
(2)
MSL Peak Temp
Op Temp (°C)
Top-Side Markings
(3)
(4)
LM2595S-12
ACTIVE
DDPAK/
TO-263
KTT
5
45
TBD
Call TI
Call TI
-40 to 125
LM2595S
-12 P+
LM2595S-12/NOPB
ACTIVE
DDPAK/
TO-263
KTT
5
45
Pb-Free (RoHS
Exempt)
CU SN
Level-3-245C-168 HR
-40 to 125
LM2595S
-12 P+
LM2595S-3.3
ACTIVE
DDPAK/
TO-263
KTT
5
45
TBD
Call TI
Call TI
LM2595S
-3.3 P+
LM2595S-3.3/NOPB
ACTIVE
DDPAK/
TO-263
KTT
5
45
Pb-Free (RoHS
Exempt)
CU SN
Level-3-245C-168 HR
LM2595S
-3.3 P+
LM2595S-5.0
ACTIVE
DDPAK/
TO-263
KTT
5
45
TBD
Call TI
Call TI
LM2595S
-5.0 P+
LM2595S-5.0/NOPB
ACTIVE
DDPAK/
TO-263
KTT
5
45
Pb-Free (RoHS
Exempt)
CU SN
Level-3-245C-168 HR
LM2595S
-5.0 P+
LM2595S-ADJ
ACTIVE
DDPAK/
TO-263
KTT
5
45
TBD
Call TI
Call TI
LM2595S
-ADJ P+
LM2595S-ADJ/NOPB
ACTIVE
DDPAK/
TO-263
KTT
5
45
Pb-Free (RoHS
Exempt)
CU SN
Level-3-245C-168 HR
LM2595S
-ADJ P+
LM2595SX-12
ACTIVE
DDPAK/
TO-263
KTT
5
500
TBD
Call TI
Call TI
-40 to 125
LM2595S
-12 P+
LM2595SX-12/NOPB
ACTIVE
DDPAK/
TO-263
KTT
5
500
Pb-Free (RoHS
Exempt)
CU SN
Level-3-245C-168 HR
-40 to 125
LM2595S
-12 P+
LM2595SX-3.3
ACTIVE
DDPAK/
TO-263
KTT
5
500
TBD
Call TI
Call TI
LM2595S
-3.3 P+
LM2595SX-3.3/NOPB
ACTIVE
DDPAK/
TO-263
KTT
5
500
Pb-Free (RoHS
Exempt)
CU SN
Level-3-245C-168 HR
LM2595S
-3.3 P+
LM2595SX-5.0
ACTIVE
DDPAK/
TO-263
KTT
5
500
TBD
Call TI
Call TI
LM2595S
-5.0 P+
LM2595SX-5.0/NOPB
ACTIVE
DDPAK/
TO-263
KTT
5
500
Pb-Free (RoHS
Exempt)
CU SN
Level-3-245C-168 HR
LM2595S
-5.0 P+
LM2595SX-ADJ
ACTIVE
DDPAK/
TO-263
KTT
5
500
TBD
Call TI
Call TI
LM2595S
-ADJ P+
LM2595SX-ADJ/NOPB
ACTIVE
DDPAK/
TO-263
KTT
5
500
Pb-Free (RoHS
Exempt)
CU SN
Level-3-245C-168 HR
LM2595S
-ADJ P+
LM2595T-12
ACTIVE
TO-220
NDH
5
45
TBD
Call TI
Call TI
Addendum-Page 1
-40 to 125
LM2595T
-12 P+
Samples
PACKAGE OPTION ADDENDUM
www.ti.com
11-Apr-2013
Orderable Device
Status
(1)
Package Type Package Pins Package
Drawing
Qty
Eco Plan
Lead/Ball Finish
(2)
MSL Peak Temp
Op Temp (°C)
Top-Side Markings
(3)
(4)
LM2595T-12/NOPB
ACTIVE
TO-220
NDH
5
45
Green (RoHS
& no Sb/Br)
CU SN
Level-1-NA-UNLIM
-40 to 125
LM2595T
-12 P+
LM2595T-3.3
ACTIVE
TO-220
NDH
5
45
TBD
Call TI
Call TI
LM2595T
-3.3 P+
LM2595T-3.3/NOPB
ACTIVE
TO-220
NDH
5
45
Green (RoHS
& no Sb/Br)
CU SN
Level-1-NA-UNLIM
LM2595T
-3.3 P+
LM2595T-5.0
ACTIVE
TO-220
NDH
5
45
TBD
Call TI
Call TI
LM2595T
-5.0 P+
LM2595T-5.0/LF02
ACTIVE
TO-220
NEB
5
45
Green (RoHS
& no Sb/Br)
CU SN
Level-1-NA-UNLIM
LM2595T
-5.0 P+
LM2595T-5.0/NOPB
ACTIVE
TO-220
NDH
5
45
Green (RoHS
& no Sb/Br)
CU SN
Level-1-NA-UNLIM
LM2595T
-5.0 P+
LM2595T-ADJ
ACTIVE
TO-220
NDH
5
45
TBD
Call TI
Call TI
LM2595T
-ADJ P+
LM2595T-ADJ/LF02
ACTIVE
TO-220
NEB
5
45
Green (RoHS
& no Sb/Br)
CU SN
Level-1-NA-UNLIM
LM2595T
-ADJ P+
LM2595T-ADJ/NOPB
ACTIVE
TO-220
NDH
5
45
Green (RoHS
& no Sb/Br)
CU SN
Level-1-NA-UNLIM
LM2595T
-ADJ P+
(1)
The marketing status values are defined as follows:
ACTIVE: Product device recommended for new designs.
LIFEBUY: TI has announced that the device will be discontinued, and a lifetime-buy period is in effect.
NRND: Not recommended for new designs. Device is in production to support existing customers, but TI does not recommend using this part in a new design.
PREVIEW: Device has been announced but is not in production. Samples may or may not be available.
OBSOLETE: TI has discontinued the production of the device.
(2)
Eco Plan - The planned eco-friendly classification: Pb-Free (RoHS), Pb-Free (RoHS Exempt), or Green (RoHS & no Sb/Br) - please check http://www.ti.com/productcontent for the latest availability
information and additional product content details.
TBD: The Pb-Free/Green conversion plan has not been defined.
Pb-Free (RoHS): TI's terms "Lead-Free" or "Pb-Free" mean semiconductor products that are compatible with the current RoHS requirements for all 6 substances, including the requirement that
lead not exceed 0.1% by weight in homogeneous materials. Where designed to be soldered at high temperatures, TI Pb-Free products are suitable for use in specified lead-free processes.
Pb-Free (RoHS Exempt): This component has a RoHS exemption for either 1) lead-based flip-chip solder bumps used between the die and package, or 2) lead-based die adhesive used between
the die and leadframe. The component is otherwise considered Pb-Free (RoHS compatible) as defined above.
Green (RoHS & no Sb/Br): TI defines "Green" to mean Pb-Free (RoHS compatible), and free of Bromine (Br) and Antimony (Sb) based flame retardants (Br or Sb do not exceed 0.1% by weight
in homogeneous material)
(3)
MSL, Peak Temp. -- The Moisture Sensitivity Level rating according to the JEDEC industry standard classifications, and peak solder temperature.
Addendum-Page 2
Samples
PACKAGE OPTION ADDENDUM
www.ti.com
11-Apr-2013
(4)
Multiple Top-Side Markings will be inside parentheses. Only one Top-Side Marking contained in parentheses and separated by a "~" will appear on a device. If a line is indented then it is a
continuation of the previous line and the two combined represent the entire Top-Side Marking for that device.
Important Information and Disclaimer:The information provided on this page represents TI's knowledge and belief as of the date that it is provided. TI bases its knowledge and belief on information
provided by third parties, and makes no representation or warranty as to the accuracy of such information. Efforts are underway to better integrate information from third parties. TI has taken and
continues to take reasonable steps to provide representative and accurate information but may not have conducted destructive testing or chemical analysis on incoming materials and chemicals.
TI and TI suppliers consider certain information to be proprietary, and thus CAS numbers and other limited information may not be available for release.
In no event shall TI's liability arising out of such information exceed the total purchase price of the TI part(s) at issue in this document sold by TI to Customer on an annual basis.
Addendum-Page 3
PACKAGE MATERIALS INFORMATION
www.ti.com
8-Apr-2013
TAPE AND REEL INFORMATION
*All dimensions are nominal
Device
Package Package Pins
Type Drawing
SPQ
Reel
Reel
A0
Diameter Width (mm)
(mm) W1 (mm)
B0
(mm)
K0
(mm)
P1
(mm)
W
Pin1
(mm) Quadrant
LM2595SX-12
DDPAK/
TO-263
KTT
5
500
330.0
24.4
10.75
14.85
5.0
16.0
24.0
Q2
LM2595SX-12/NOPB
DDPAK/
TO-263
KTT
5
500
330.0
24.4
10.75
14.85
5.0
16.0
24.0
Q2
LM2595SX-3.3
DDPAK/
TO-263
KTT
5
500
330.0
24.4
10.75
14.85
5.0
16.0
24.0
Q2
LM2595SX-3.3/NOPB
DDPAK/
TO-263
KTT
5
500
330.0
24.4
10.75
14.85
5.0
16.0
24.0
Q2
LM2595SX-5.0
DDPAK/
TO-263
KTT
5
500
330.0
24.4
10.75
14.85
5.0
16.0
24.0
Q2
LM2595SX-5.0/NOPB
DDPAK/
TO-263
KTT
5
500
330.0
24.4
10.75
14.85
5.0
16.0
24.0
Q2
LM2595SX-ADJ
DDPAK/
TO-263
KTT
5
500
330.0
24.4
10.75
14.85
5.0
16.0
24.0
Q2
LM2595SX-ADJ/NOPB
DDPAK/
TO-263
KTT
5
500
330.0
24.4
10.75
14.85
5.0
16.0
24.0
Q2
Pack Materials-Page 1
PACKAGE MATERIALS INFORMATION
www.ti.com
8-Apr-2013
*All dimensions are nominal
Device
Package Type
Package Drawing
Pins
SPQ
Length (mm)
Width (mm)
Height (mm)
LM2595SX-12
DDPAK/TO-263
KTT
5
500
367.0
367.0
45.0
LM2595SX-12/NOPB
DDPAK/TO-263
KTT
5
500
367.0
367.0
45.0
LM2595SX-3.3
DDPAK/TO-263
KTT
5
500
367.0
367.0
45.0
LM2595SX-3.3/NOPB
DDPAK/TO-263
KTT
5
500
367.0
367.0
45.0
LM2595SX-5.0
DDPAK/TO-263
KTT
5
500
367.0
367.0
45.0
LM2595SX-5.0/NOPB
DDPAK/TO-263
KTT
5
500
367.0
367.0
45.0
LM2595SX-ADJ
DDPAK/TO-263
KTT
5
500
367.0
367.0
45.0
LM2595SX-ADJ/NOPB
DDPAK/TO-263
KTT
5
500
367.0
367.0
45.0
Pack Materials-Page 2
MECHANICAL DATA
NDH0005D
www.ti.com
MECHANICAL DATA
KTT0005B
TS5B (Rev D)
BOTTOM SIDE OF PACKAGE
www.ti.com
MECHANICAL DATA
NEB0005B
www.ti.com
IMPORTANT NOTICE
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changes to its semiconductor products and services per JESD46, latest issue, and to discontinue any product or service per JESD48, latest
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TI warrants performance of its components to the specifications applicable at the time of sale, in accordance with the warranty in TI’s terms
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