LM2596T-12 - Texas Instruments High-Performance Analog

LM2596

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SNVS124C –NOVEMBER 1999–REVISED APRIL 2013

LM2596 SIMPLE SWITCHER

Power Converter 150 kHz

3A Step-Down Voltage Regulator

Check for Samples: LM2596

1FEATURES DESCRIPTION

The LM2596 series of regulators are monolithic

23• 3.3V, 5V, 12V, and Adjustable Output Versions integrated circuits that provide all the active functions

• Adjustable Version Output Voltage Range, for a step-down (buck) switching regulator, capable of

1.2V to 37V ±4% Max Over Line and Load driving a 3A load with excellent line and load

Conditions regulation. These devices are available in fixed output

voltages of 3.3V, 5V, 12V, and an adjustable output

• Available in TO-220 and TO-263 Packages version.

• Ensured 3A Output Load Current Requiring a minimum number of external

• Input Voltage Range Up to 40V components, these regulators are simple to use and

• Requires Only 4 External Components include internal frequency compensation , and a

• Excellent Line and Load Regulation fixed-frequency oscillator.

Specifications The LM2596 series operates at a switching frequency

• 150 kHz Fixed Frequency Internal Oscillator of 150 kHz thus allowing smaller sized filter

• TTL Shutdown Capability components than what would be needed with lower

frequency switching regulators. Available in a

• Low Power Standby Mode, IQTypically 80 μAstandard 5-lead TO-220 package with several

• High Efficiency different lead bend options, and a 5-lead TO-263

• Uses Readily Available Standard Inductors surface mount package.

• Thermal Shutdown and Current Limit A standard series of inductors are available from

Protection several different manufacturers optimized for use with

the LM2596 series. This feature greatly simplifies the

APPLICATIONS design of switch-mode power supplies.

• Simple High-Efficiency Step-Down (Buck) Other features include a ensured ±4% tolerance on

Regulator output voltage under specified input voltage and

output load conditions, and ±15% on the oscillator

• On-Card Switching Regulators frequency. External shutdown is included, featuring

• Positive to Negative Converter 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. (1)

(1) † Patent Number 5,382,918.

Typical Application

(Fixed Output Voltage Versions)

1Please 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.

2SIMPLE SWITCHER is a registered trademark of Texas Instruments.

3All other trademarks are the property of their respective owners.

Products conform to specifications per the terms of the Texas

Instruments standard warranty. Production processing does not

necessarily include testing of all parameters.

LM2596

SNVS124C –NOVEMBER 1999–REVISED APRIL 2013

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Connection Diagrams

Figure 1. 5-Lead Bent and Staggered Leads, Figure 2. 5-Lead DDPAK/TO-263 (S) Package

Through Hole TO-220 (T) Package See Package Number KTT0005B

See Package Number NDH0005D

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 (Steady State) −1V

Power Dissipation Internally limited

Storage Temperature Range −65°C to +150°C

ESD Susceptibility

Human Body Model (3) 2 kV

Lead Temperature

DDPAK/TO-263 Package

Vapor Phase (60 sec.) +215°C

Infrared (10 sec.) +245°C

TO-220 Package (Soldering, 10 sec.) +260°C

Maximum Junction Temperature +150°C

(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 ensure specific performance limits. For ensured specifications and test

conditions, see the Electrical Characteristics.

(2) If Military/Aerospace specified devices are required, please contact the Texas Instruments Sales Office/ Distributors for availability and

specifications.

(3) The human body model is a 100 pF capacitor discharged through a 1.5k resistor into each pin.

Operating Conditions

Temperature Range −40°C ≤TJ≤+125°C

Supply Voltage 4.5V to 40V

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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

LM2596-3.3 Units

Symbol Parameter Conditions Typ Limit (Limits)

(1) (2)

SYSTEM PARAMETERS (3) Test Circuit Figure 20

VOUT Output Voltage 4.75V ≤VIN ≤40V, 0.2A ≤ILOAD ≤3A 3.3 V

3.168/3.135 V(min)

3.432/3.465 V(max)

ηEfficiency VIN = 12V, ILOAD = 3A 73 %

(1) Typical numbers are at 25°C and represent the most likely norm.

(2) 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 ensured via correlation using standard Statistical Quality Control

(SQC) methods. All limits are used to calculate Average Outgoing Quality Level (AOQL).

(3) External components such as the catch diode, inductor, input and output capacitors, and voltage programming resistors can affect

switching regulator system performance. When the LM2596 is used as shown in the Figure 20 test circuit, system performance will be

as shown in system parameters of Electrical Characteristics section.

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

LM2596-5.0 Units

Symbol Parameter Conditions Typ Limit (Limits)

(1) (2)

SYSTEM PARAMETERS (3) Test Circuit Figure 20

VOUT Output Voltage 7V ≤VIN ≤40V, 0.2A ≤ILOAD ≤3A 5.0 V

4.800/4.750 V(min)

5.200/5.250 V(max)

ηEfficiency VIN = 12V, ILOAD = 3A 80 %

(1) Typical numbers are at 25°C and represent the most likely norm.

(2) 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 ensured via correlation using standard Statistical Quality Control

(SQC) methods. All limits are used to calculate Average Outgoing Quality Level (AOQL).

(3) External components such as the catch diode, inductor, input and output capacitors, and voltage programming resistors can affect

switching regulator system performance. When the LM2596 is used as shown in the Figure 20 test circuit, system performance will be

as shown in system parameters of Electrical Characteristics section.

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

LM2596-12 Units

Symbol Parameter Conditions Typ Limit (Limits)

(1) (2)

SYSTEM PARAMETERS (3) Test Circuit Figure 20

VOUT Output Voltage 15V ≤VIN ≤40V, 0.2A ≤ILOAD ≤3A 12.0 V

11.52/11.40 V(min)

12.48/12.60 V(max)

ηEfficiency VIN = 25V, ILOAD = 3A 90 %

(1) Typical numbers are at 25°C and represent the most likely norm.

(2) 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 ensured via correlation using standard Statistical Quality Control

(SQC) methods. All limits are used to calculate Average Outgoing Quality Level (AOQL).

(3) External components such as the catch diode, inductor, input and output capacitors, and voltage programming resistors can affect

switching regulator system performance. When the LM2596 is used as shown in the Figure 20 test circuit, system performance will be

as shown in system parameters of Electrical Characteristics section.

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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

LM2596-ADJ Units

Symbol Parameter Conditions Typ Limit (Limits)

(1) (2)

SYSTEM PARAMETERS (3) Test Circuit Figure 20

VFB Feedback Voltage 4.5V ≤VIN ≤40V, 0.2A ≤ILOAD ≤3A 1.230 V

VOUT programmed for 3V. Circuit of Figure 20 1.193/1.180 V(min)

1.267/1.280 V(max)

ηEfficiency VIN = 12V, VOUT = 3V, ILOAD = 3A 73 %

(1) Typical numbers are at 25°C and represent the most likely norm.

(2) 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 ensured via correlation using standard Statistical Quality Control

(SQC) methods. All limits are used to calculate Average Outgoing Quality Level (AOQL).

(3) External components such as the catch diode, inductor, input and output capacitors, and voltage programming resistors can affect

switching regulator system performance. When the LM2596 is used as shown in the Figure 20 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 = 500 mA LM2596-XX Units

Symbol Parameter Conditions Typ Limit (Limits)

(1) (2)

DEVICE PARAMETERS

IbFeedback Bias Current Adjustable Version Only, VFB = 1.3V 10 nA

50/100 nA (max)

fOOscillator Frequency See (3) 150 kHz

127/110 kHz(min)

173/173 kHz(max)

VSAT Saturation Voltage IOUT = 3A (4) (5) 1.16 V

1.4/1.5 V(max)

DC Max Duty Cycle (ON) See (5) 100 %

Min Duty Cycle (OFF) See (6) 0

ICL Current Limit Peak Current (4)(5) 4.5 A

3.6/3.4 A(min)

6.9/7.5 A(max)

ILOutput Leakage Current Output = 0V (4)(6) 50 μA(max)

Output = −1V (7) 2 mA

30 mA(max)

IQQuiescent Current See (6) 5 mA

10 mA(max)

(1) Typical numbers are at 25°C and represent the most likely norm.

(2) 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 ensured via correlation using standard Statistical Quality Control

(SQC) methods. All limits are used to calculate Average Outgoing Quality Level (AOQL).

(3) The switching frequency is reduced when the second stage current limit is activated.

(4) No diode, inductor or capacitor connected to output pin.

(5) Feedback pin removed from output and connected to 0V to force the output transistor switch ON.

(6) 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.

(7) VIN = 40V.

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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 = 500 mA LM2596-XX Units

Symbol Parameter Conditions Typ Limit (Limits)

(1) (2)

ISTBY Standby Quiescent Current ON/OFF pin = 5V (OFF) (7) 80 μA

200/250 μA(max)

θJC Thermal Resistance TO-220 or TO-263 Package, Junction to Case 2 °C/W

θJA 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

ON/OFF CONTROL Test Circuit Figure 20

ON /OFF Pin Logic Input 1.3 V

VIH Threshold Voltage Low (Regulator ON) 0.6 V(max)

VIL High (Regulator OFF) 2.0 V(min)

IHON /OFF Pin Input Current VLOGIC = 2.5V (Regulator OFF) 5 μA

15 μA(max)

ILVLOGIC = 0.5V (Regulator ON) 0.02 μA

5μA(max)

(8) 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 in2of (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 in2of (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 in2of (1 oz.)

copper area on the LM2596S side of the board, and approximately 16 in2of 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 20)

Normalized

Output Voltage Line Regulation

Figure 3. Figure 4.

Switch Saturation

Efficiency Voltage

Figure 5. Figure 6.

Switch Current Limit Dropout Voltage

Figure 7. Figure 8.

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Typical Performance Characteristics (continued)

(Circuit of Figure 20)Operating Shutdown

Quiescent Current Quiescent Current

Figure 9. Figure 10.

Minimum Operating ON /OFF Threshold

Supply Voltage Voltage

Figure 11. Figure 12.

ON /OFF Pin

Current (Sinking) Switching Frequency

Figure 13. Figure 14.

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Typical Performance Characteristics (continued)

(Circuit of Figure 20)Continuous Mode Switching Waveforms

Feedback Pin VIN = 20V, VOUT = 5V, ILOAD = 2A

Bias Current L = 32 μH, COUT = 220 μF, COUT ESR = 50 mΩ

A: Output Pin Voltage, 10V/div.

B: Inductor Current 1A/div.

C: Output Ripple Voltage, 50 mV/div.

Figure 15. Figure 16. Horizontal Time Base: 2 μs/div.

Discontinuous Mode Switching Waveforms Load Transient Response for Continuous Mode

VIN = 20V, VOUT = 5V, ILOAD = 500 mA VIN = 20V, VOUT = 5V, ILOAD = 500 mA to 2A

L = 10 μH, COUT = 330 μF, COUT ESR = 45 mΩL = 32 μH, COUT = 220 μF, COUT ESR = 50 mΩ

A: Output Voltage, 100 mV/div. (AC)

A: Output Pin Voltage, 10V/div. B: 500 mA to 2A Load Pulse

B: Inductor Current 0.5A/div.

C: Output Ripple Voltage, 100 mV/div.

Figure 17. Horizontal Time Base: 2 μs/div. Figure 18. Horizontal Time Base: 100 μs/div.

Load Transient Response for Discontinuous Mode

VIN = 20V, VOUT = 5V, ILOAD = 500 mA to 2A

L = 10 μH, COUT = 330 μF, COUT ESR = 45 mΩ

A: Output Voltage, 100 mV/div. (AC)

B: 500 mA to 2A Load Pulse Figure 19. Horizontal Time Base: 200 μs/div.

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Test Circuit and Layout Guidelines

Fixed Output Voltage Versions

CIN —470 μF, 50V, Aluminum Electrolytic Nichicon “PL Series”

COUT —220 μF, 25V Aluminum Electrolytic, Nichicon “PL Series”

D1 —5A, 40V Schottky Rectifier, 1N5825

L1 —68 μH, L38

Adjustable Output Voltage Versions

where VREF = 1.23V

Select R1to be approximately 1 kΩ, use a 1% resistor for best stability.

CIN —470 μF, 50V, Aluminum Electrolytic Nichicon “PL Series”

COUT —220 μF, 35V Aluminum Electrolytic, Nichicon “PL Series”

D1 —5A, 40V Schottky Rectifier, 1N5825

L1 —68 μH, L38

R1 —1 kΩ, 1%

CFF —See Application Information Section

Figure 20. 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.

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.)

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LM2596

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LM2596 Series Buck Regulator Design Procedure (Fixed Output)

PROCEDURE (Fixed Output Voltage Version) EXAMPLE (Fixed Output Voltage Version)

Given: Given:

VOUT = Regulated Output Voltage (3.3V, 5V or 12V) VOUT = 5V

VIN(max) = Maximum DC Input Voltage VIN(max) = 12V

ILOAD(max) = Maximum Load Current ILOAD(max) = 3A

1. Inductor Selection (L1) 1. Inductor Selection (L1)

A. Select the correct inductor value selection guide from Figures A. Use the inductor selection guide for the 5V version shown in

Figure 21,Figure 22, or Figure 23. (Output voltages of 3.3V, 5V, or Figure 22.

12V respectively.) For all other voltages, see the Design Procedure B. From the inductor value selection guide shown in Figure 22, the

for the adjustable version. inductance region intersected by the 12V horizontal line and the 3A

B. From the inductor value selection guide, identify the inductance vertical line is 33 μH, and the inductor code is L40.

region intersected by the Maximum Input Voltage line and the C. The inductance value required is 33 μH. From the table in

Maximum Load Current line. Each region is identified by an Table 3, go to the L40 line and choose an inductor part number from

inductance value and an inductor code (LXX). any of the four manufacturers shown. (In most instance, both

C. Select an appropriate inductor from the four manufacturer's part through hole and surface mount inductors are available.)

numbers listed in Table 3.

2. Output Capacitor Selection (COUT) 2. Output Capacitor Selection (COUT)

A. In the majority of applications, low ESR (Equivalent Series A. See section on output capacitors in Application Information

Resistance) electrolytic capacitors between 82 μF and 820 μF and section.

low ESR solid tantalum capacitors between 10 μF and 470 μFB. From the quick design component selection table shown in

provide the best results. This capacitor should be located close to Table 1, locate the 5V output voltage section. In the load current

the IC using short capacitor leads and short copper traces. Do not column, choose the load current line that is closest to the current

use capacitors larger than 820 μF . needed in your application, for this example, use the 3A line. In the

For additional information, see section on output capacitors in maximum input voltage column, select the line that covers the input

Application Information section. voltage needed in your application, in this example, use the 15V line.

Continuing on this line are recommended inductors and capacitors

B. To simplify the capacitor selection procedure, refer to the quick that will provide the best overall performance.

design component selection table shown in Table 1. This table

contains different input voltages, output voltages, and load currents, The capacitor list contains both through hole electrolytic and surface

and lists various inductors and output capacitors that will provide the mount tantalum capacitors from four different capacitor

best design solutions. manufacturers. It is recommended that both the manufacturers and

the manufacturer's series that are listed in the table be used.

C. The capacitor voltage rating for electrolytic capacitors should be

at least 1.5 times greater than the output voltage, and often much In this example aluminum electrolytic capacitors from several

higher voltage ratings are needed to satisfy the low ESR different manufacturers are available with the range of ESR numbers

requirements for low output ripple voltage. needed.

D. For computer aided design software, see Switchers Made 330 μF 35V Panasonic HFQ Series

Simple™ version 4.3 or later. 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 26 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.

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PROCEDURE (Fixed Output Voltage Version) EXAMPLE (Fixed Output Voltage Version)

3. Catch Diode Selection (D1) 3. Catch Diode Selection (D1)

A. The catch diode current rating must be at least 1.3 times greater A. Refer to the table shown in Table 6. In this example, a 5A, 20V,

than the maximum load current. Also, if the power supply design 1N5823 Schottky diode will provide the best performance, and will

must withstand a continuous output short, the diode should have a not be overstressed even for a shorted output.

current rating equal to the maximum current limit of the LM2596. 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 LM2596 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.

4. Input Capacitor (CIN) 4. Input Capacitor (CIN)

A low ESR aluminum or tantalum bypass capacitor is needed The important parameters for the Input capacitor are the input

between the input pin and ground pin to prevent large voltage voltage rating and the RMS current rating. With a nominal input

transients from appearing at the input. This capacitor should be voltage of 12V, an aluminum electrolytic capacitor with a voltage

located close to the IC using short leads. In addition, the RMS rating greater than 18V (1.5 × VIN) would be needed. The next

current rating of the input capacitor should be selected to be at least higher capacitor voltage rating is 25V.

½ the DC load current. The capacitor manufacturers data sheet must The RMS current rating requirement for the input capacitor in a buck

be checked to assure that this current rating is not exceeded. The regulator is approximately ½ the DC load current. In this example,

curve shown in Figure 25 shows typical RMS current ratings for with a 3A load, a capacitor with a RMS current rating of at least 1.5A

several different aluminum electrolytic capacitor values. is needed. The curves shown in Figure 25 can be used to select an

For an aluminum electrolytic, the capacitor voltage rating should be appropriate input capacitor. From the curves, locate the 35V line and

approximately 1.5 times the maximum input voltage. Caution must note which capacitor values have RMS current ratings greater than

be exercised if solid tantalum capacitors are used (see Application 1.5A. A 680 μF/35V capacitor could be used.

Information on input capacitor). The tantalum capacitor voltage rating For a through hole design, a 680 μF/35V electrolytic capacitor

should be 2 times the maximum input voltage and it is recommended (Panasonic HFQ series or Nichicon PL series or equivalent) would

that they be surge current tested by the manufacturer. be adequate. other types or other manufacturers capacitors can be

Use caution when using ceramic capacitors for input bypassing, used provided the RMS ripple current ratings are adequate.

because it may cause severe ringing at the VIN pin. For surface mount designs, solid tantalum capacitors can be used,

For additional information, see section on input capacitors in but caution must be exercised with regard to the capacitor surge

Application Information section. 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 1. LM2596 Fixed Voltage Quick Design Component Selection Table

Conditions Inductor Output Capacitor

Through Hole Electrolytic Surface Mount Tantalum

Output Load Max Input Panasonic Nichicon AVX TPS Sprague

Inductance Inductor

Voltage Current Voltage HFQ Series PL Series Series 595D Series

(μH) (#)

(V) (A) (V) (μF/V) (μF/V) (μF/V) (μF/V)

3.3 3 5 22 L41 470/25 560/16 330/6.3 390/6.3

7 22 L41 560/35 560/35 330/6.3 390/6.3

10 22 L41 680/35 680/35 330/6.3 390/6.3

40 33 L40 560/35 470/35 330/6.3 390/6.3

6 22 L33 470/25 470/35 330/6.3 390/6.3

2 10 33 L32 330/35 330/35 330/6.3 390/6.3

40 47 L39 330/35 270/50 220/10 330/10

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Table 1. LM2596 Fixed Voltage Quick Design Component Selection Table (continued)

Conditions Inductor Output Capacitor

Through Hole Electrolytic Surface Mount Tantalum

Output Load Max Input Panasonic Nichicon AVX TPS Sprague

Inductance Inductor

Voltage Current Voltage HFQ Series PL Series Series 595D Series

(μH) (#)

(V) (A) (V) (μF/V) (μF/V) (μF/V) (μF/V)

53 8 22 L41 470/25 560/16 220/10 330/10

10 22 L41 560/25 560/25 220/10 330/10

15 33 L40 330/35 330/35 220/10 330/10

40 47 L39 330/35 270/35 220/10 330/10

9 22 L33 470/25 560/16 220/10 330/10

2 20 68 L38 180/35 180/35 100/10 270/10

40 68 L38 180/35 180/35 100/10 270/10

12 3 15 22 L41 470/25 470/25 100/16 180/16

18 33 L40 330/25 330/25 100/16 180/16

30 68 L44 180/25 180/25 100/16 120/20

40 68 L44 180/35 180/35 100/16 120/20

15 33 L32 330/25 330/25 100/16 180/16

2 20 68 L38 180/25 180/25 100/16 120/20

40 150 L42 82/25 82/25 68/20 68/25

LM2596 Series Buck Regulator Design Procedure (Adjustable Output)

PROCEDURE (Adjustable Output Voltage Version) EXAMPLE (Adjustable Output Voltage Version)

Given: Given:

VOUT = Regulated Output Voltage VOUT = 20V

VIN(max) = Maximum Input Voltage VIN(max) = 28V

ILOAD(max) = Maximum Load Current ILOAD(max) = 3A

F = Switching Frequency (Fixed at a nominal 150 kHz). F = Switching Frequency (Fixed at a nominal 150 kHz).

1. Programming Output Voltage (Selecting R1and R2, as shown in 1. Programming Output Voltage (Selecting R1and R2, as shown in

Figure 20 )Figure 20 )

Use the following formula to select the appropriate resistor values. Select R1to be 1 kΩ, 1%. Solve for R2.

(3)

(1) R2= 1k (16.26 −1) = 15.26k, closest 1% value is 15.4 kΩ.

Select a value for R1between 240Ωand 1.5 kΩ. The lower resistor

values minimize noise pickup in the sensitive feedback pin. (For the R2= 15.4 kΩ.

lowest temperature coefficient and the best stability with time, use

1% metal film resistors.)

(2)

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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

from the following formula: (E • T),

where (5)

• VSAT = internal switch saturation voltage = B. E • T = 34.2 (V • μs)

1.16V C. ILOAD(max) = 3A

• VD= diode forward voltage drop = 0.5V (4) D. From the inductor value selection guide shown in Figure 24, the

inductance region intersected by the 34 (V • μs) horizontal line and

the 3A vertical line is 47 μH, and the inductor code is L39.

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 E. From the table in Table 3,locate line L39, and select an inductor

Guide shown in Figure 24.part number from the list of manufacturers part numbers.

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 3.

3. Output Capacitor Selection (COUT) 3. Output Capacitor SeIection (COUT)

A. In the majority of applications, low ESR electrolytic or solid A. See section on COUT in Application Information section.

tantalum capacitors between 82 μF and 820 μF provide the best B. From the quick design table shown in Table 2, locate the output

results. This capacitor should be located close to the IC using short voltage column. From that column, locate the output voltage closest

capacitor leads and short copper traces. Do not use capacitors to the output voltage in your application. In this example, select the

larger than 820 μF. For additional information, see section on 24V line. Under the OUTPUT CAPACITOR section, select a

output capacitors in Application Information section. capacitor from the list of through hole electrolytic or surface mount

B. To simplify the capacitor selection procedure, refer to the quick tantalum types from four different capacitor manufacturers. It is

design table shown in Table 2. This table contains different output recommended that both the manufacturers and the manufacturers

voltages, and lists various output capacitors that will provide the best series that are listed in the table be used.

design solutions. In this example, through hole aluminum electrolytic capacitors from

C. The capacitor voltage rating should be at least 1.5 times greater several different manufacturers are available.

than the output voltage, and often much higher voltage ratings are 220 μF/35V Panasonic HFQ Series

needed to satisfy the low ESR requirements needed for low output 150 μF/35V Nichicon PL Series

ripple voltage. 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 20)4. Feedforward Capacitor (CFF)

For output voltages greater than approximately 10V, an additional The table shown in Table 2 contains feed forward capacitor values

capacitor is required. The compensation capacitor is typically for various output voltages. In this example, a 560 pF capacitor is

between 100 pF and 33 nF, and is wired in parallel with the output needed.

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.

(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.)

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PROCEDURE (Adjustable Output Voltage Version) EXAMPLE (Adjustable Output Voltage Version)

5. Catch Diode Selection (D1) 5. Catch Diode Selection (D1)

A. The catch diode current rating must be at least 1.3 times greater A. Refer to the table shown in Table 6. Schottky diodes provide the

than the maximum load current. Also, if the power supply design best performance, and in this example a 5A, 40V, 1N5825 Schottky

must withstand a continuous output short, the diode should have a diode would be a good choice. The 5A diode rating is more than

current rating equal to the maximum current limit of the LM2596. The adequate and will not be overstressed even for a shorted output.

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 LM2596 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.

6. Input Capacitor (CIN) 6. Input Capacitor (CIN)

A low ESR aluminum or tantalum bypass capacitor is needed The important parameters for the Input capacitor are the input

between the input pin and ground to prevent large voltage transients voltage rating and the RMS current rating. With a nominal input

from appearing at the input. In addition, the RMS current rating of voltage of 28V, an aluminum electrolytic aluminum electrolytic

the input capacitor should be selected to be at least ½ the DC load capacitor with a voltage rating greater than 42V (1.5 × VIN) would be

current. The capacitor manufacturers data sheet must be checked to needed. Since the the next higher capacitor voltage rating is 50V, a

assure that this current rating is not exceeded. The curve shown in 50V capacitor should be used. The capacitor voltage rating of (1.5 ×

Figure 25 shows typical RMS current ratings for several different VIN) is a conservative guideline, and can be modified somewhat if

aluminum electrolytic capacitor values. desired.

This capacitor should be located close to the IC using short leads The RMS current rating requirement for the input capacitor of a buck

and the voltage rating should be approximately 1.5 times the regulator is approximately ½ the DC load current. In this example,

maximum input voltage. with a 3A load, a capacitor with a RMS current rating of at least 1.5A

is needed.

If solid tantalum input capacitors are used, it is recomended that they

be surge current tested by the manufacturer. The curves shown in Figure 25 can be used to select an appropriate

input capacitor. From the curves, locate the 50V line and note which

Use caution when using a high dielectric constant ceramic capacitor capacitor values have RMS current ratings greater than 1.5A. Either

for input bypassing, because it may cause severe ringing at the VIN a 470 μF or 680 μF, 50V capacitor could be used.

pin. For a through hole design, a 680 μF/50V electrolytic capacitor

For additional information, see section on input capacitors in (Panasonic HFQ series or Nichicon PL series or equivalent) would

Application Information section. 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 4.3 or later) is available on a 3½″

diskette for IBM compatible computers.

LM2596 Series Buck Regulator Design Procedure (Adjustable Output)

Table 2. Output Capacitor and Feedforward Capacitor Selection Table

Output Through Hole Output Capacitor Surface Mount Output Capacitor

Voltage Panasonic Nichicon PL AVX TPS Sprague

Feedforward Feedforward

(V) HFQ Series Series Series 595D Series

Capacitor Capacitor

(μF/V) (μF/V) (μF/V) (μF/V)

2820/35 820/35 33 nF 330/6.3 470/4 33 nF

4560/35 470/35 10 nF 330/6.3 390/6.3 10 nF

6470/25 470/25 3.3 nF 220/10 330/10 3.3 nF

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Table 2. Output Capacitor and Feedforward Capacitor Selection Table (continued)

Output Through Hole Output Capacitor Surface Mount Output Capacitor

Voltage Panasonic Nichicon PL AVX TPS Sprague

Feedforward Feedforward

(V) HFQ Series Series Series 595D Series

Capacitor Capacitor

(μF/V) (μF/V) (μF/V) (μF/V)

9330/25 330/25 1.5 nF 100/16 180/16 1.5 nF

1 2 330/25 330/25 1 nF 100/16 180/16 1 nF

1 5 220/35 220/35 680 pF 68/20 120/20 680 pF

2 4 220/35 150/35 560 pF 33/25 33/25 220 pF

2 8 100/50 100/50 390 pF 10/35 15/50 220 pF

LM2596 Series Buck Regulator Design Procedure

INDUCTOR VALUE SELECTION GUIDES

(For Continuous Mode Operation)

Figure 21. LM2596-3.3 Figure 22. LM2596-5.0

Figure 23. LM2596-12 Figure 24. LM2596-ADJ

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Table 3. Inductor Manufacturers Part Numbers

Inductance Current Schott Renco Pulse Engineering Coilcraft

(μH) (A) Through Surface Through Surface Through Surface Surface

Hole Mount Hole Mount Hole Mount Mount

L15 22 0.99 67148350 67148460 RL-1284-22-43 RL1500-22 PE-53815 PE-53815-S DO3308-223

L21 68 0.99 67144070 67144450 RL-5471-5 RL1500-68 PE-53821 PE-53821-S DO3316-683

L22 47 1.17 67144080 67144460 RL-5471-6 — PE-53822 PE-53822-S DO3316-473

L23 33 1.40 67144090 67144470 RL-5471-7 — PE-53823 PE-53823-S DO3316-333

L24 22 1.70 67148370 67148480 RL-1283-22-43 — PE-53824 PE-53825-S DO3316-223

L25 15 2.10 67148380 67148490 RL-1283-15-43 — PE-53825 PE-53824-S DO3316-153

L26 330 0.80 67144100 67144480 RL-5471-1 — PE-53826 PE-53826-S DO5022P-334

L27 220 1.00 67144110 67144490 RL-5471-2 — PE-53827 PE-53827-S DO5022P-224

L28 150 1.20 67144120 67144500 RL-5471-3 — PE-53828 PE-53828-S DO5022P-154

L29 100 1.47 67144130 67144510 RL-5471-4 — PE-53829 PE-53829-S DO5022P-104

L30 68 1.78 67144140 67144520 RL-5471-5 — PE-53830 PE-53830-S DO5022P-683

L31 47 2.20 67144150 67144530 RL-5471-6 — PE-53831 PE-53831-S DO5022P-473

L32 33 2.50 67144160 67144540 RL-5471-7 — PE-53932 PE-53932-S DO5022P-333

L33 22 3.10 67148390 67148500 RL-1283-22-43 — PE-53933 PE-53933-S DO5022P-223

L34 15 3.40 67148400 67148790 RL-1283-15-43 — PE-53934 PE-53934-S DO5022P-153

L35 220 1.70 67144170 — RL-5473-1 — PE-53935 PE-53935-S —

L36 150 2.10 67144180 — RL-5473-4 — PE-54036 PE-54036-S —

L37 100 2.50 67144190 — RL-5472-1 — PE-54037 PE-54037-S —

L38 68 3.10 67144200 — RL-5472-2 — PE-54038 PE-54038-S —

L39 47 3.50 67144210 — RL-5472-3 — PE-54039 PE-54039-S —

L40 33 3.50 67144220 67148290 RL-5472-4 — PE-54040 PE-54040-S —

L41 22 3.50 67144230 67148300 RL-5472-5 — PE-54041 PE-54041-S —

L42 150 2.70 67148410 — RL-5473-4 — PE-54042 PE-54042-S —

L43 100 3.40 67144240 — RL-5473-2 — PE-54043 —

L44 68 3.40 67144250 — RL-5473-3 — PE-54044 —

Table 4. Inductor Manufacturers Phone Numbers

Coilcraft Inc. Phone (800) 322-2645

FAX (708) 639-1469

Coilcraft Inc., Europe Phone +11 1236 730 595

FAX +44 1236 730 627

Pulse Engineering Inc. Phone (619) 674-8100

FAX (619) 674-8262

Pulse Engineering Inc., Europe Phone +353 93 24 107

FAX +353 93 24 459

Renco Electronics Inc. Phone (800) 645-5828

FAX (516) 586-5562

Schott Corp. Phone (612) 475-1173

FAX (612) 475-1786

Table 5. Capacitor Manufacturers Phone Numbers

Nichicon Corp. Phone (708) 843-7500

FAX (708) 843-2798

Panasonic Phone (714) 373-7857

FAX (714) 373-7102

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Table 5. Capacitor Manufacturers Phone Numbers (continued)

AVX Corp. Phone (803) 448-9411

FAX (803) 448-1943

Sprague/Vishay Phone (207) 324-4140

FAX (207) 324-7223

Table 6. Diode Selection Table

VR 3A Diodes 4A–6A Diodes

Surface Mount Through Hole Surface Mount Through Hole

Schottky Ultra Fast Schottky Ultra Fast Schottky Ultra Fast Schottky Ultra Fast

Recovery Recovery Recovery Recovery

20V All of 1N5820 All of All of SR502 All of

these these these these

SK32 SR302 1N5823

diodes diodes diodes diodes

MBR320 SB520

are are are are

rated to rated to rated to rated to

30V 30WQ03 1N5821

at least at least at least at least

SK33 MBR330 50WQ03 SR503

50V. 50V. 50V. 50V.

31DQ03 1N5824

1N5822 SB530

40V SK34 SR304 50WQ04 SR504

MBRS340 MBR340 1N5825

30WQ04 MURS320 31DQ04 MUR320 MURS620 SB540 MUR620

50V SK35 30WF10 SR305 50WF10 HER601

or MBRS360 MBR350 50WQ05 SB550

More 30WQ05 31DQ05 50SQ080

Block Diagram

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APPLICATION INFORMATION

Table 7. PIN DESCRIPTIONS

Name Description

This is the positive input supply for the IC switching regulator. A suitable input bypass

+VIN capacitor must be present at this pin to minimize voltage transients and to supply the

switching currents needed by the regulator.

Ground Circuit ground.

Internal switch. The voltage at this pin switches between (+VIN −VSAT) and approximately

Output −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.

Allows the switching regulator circuit to be shut down using logic level signals thus dropping

the total input supply current to approximately 80 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

ON /OFF 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 25 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 20 is used when the ouput 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 25. 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 26 ). 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 1 and 4for 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 27.

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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 26. 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 LM2596 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 27. 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 LM2596 (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 21

through 8). 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 28.)

Figure 28. (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 torroid 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 LM2596. 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 (1A 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.

Figure 29. 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 20.)

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 29 shows a typical output ripple voltage, with and without a post ripple filter.

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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.

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 30. 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 21 through 8are used to select an inductor value, the peak-to-peak inductor ripple current can

immediately be determined. The curve shown in Figure 30 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 section).

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 2.5A

VIN = 12V, nominal, varying between 10V and 16V.

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The selection guide in Figure 22 shows that the vertical line for a 2.5A load current, and the horizontal line for the

12V input voltage intersect approximately midway between the upper and lower borders of the 33 μH inductance

region. A 33 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 30, follow the 2.5A line approximately midway into the inductance

region, and read the peak-to-peak inductor ripple current (ΔIIND) on the left hand axis (approximately 620 mA p-

p).

As the input voltage increases to 16V, it approaches the upper border of the inductance region, and the inductor

ripple current increases. Referring to the curve in Figure 30, it can be seen that for a load current of 2.5A, the

peak-to-peak inductor ripple current (ΔIIND) is 620 mA with 12V in, and can range from 740 mA at the upper

border (16V in) to 500 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) = 0.62A×0.1Ω= 62 mV p-p

4. added for line break

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 in- ductor 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.

Product Folder Links: LM2596

LM2596

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SNVS124C –NOVEMBER 1999–REVISED APRIL 2013

THERMAL CONSIDERATIONS

The LM2596 is available in two packages, a 5-pin TO-220 (T) and a 5-pin surface mount TO-263 (S).

The TO-220 package needs a heat sink under most conditions. The size of the heatsink depends on the input

voltage, the output voltage, the load current and the ambient temperature. The curves in Figure 31 show the

LM2596T junction temperature rises above ambient temperature for a 3A load and different input and output

voltages. The data for these curves was taken with the LM2596T (TO-220 package) operating as a buck

switching regulator 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

more heat sinking.

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 6 in2, only small improvements in

heat dissipation are realized. If further thermal improvements are needed, double sided, multilayer PC board with

large copper areas and/or airflow are recommended.

The curves shown in Figure 32 show the LM2596S (TO-263 package) junction temperature rise above ambient

temperature with a 2A 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. When load currents higher than 2A are used, double sided or multilayer PC boards with large

copper areas and/or airflow might be needed, especially for high ambient temperatures and high output voltages.

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.

Product Folder Links: LM2596

LM2596

SNVS124C –NOVEMBER 1999–REVISED APRIL 2013

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Circuit Data for Temperature Rise Curve

TO-220 Package (T)

Capacitors Through hole electrolytic

Inductor Through hole, Renco

Diode Through hole, 5A 40V, Schottky

PC board 3 square inches single sided 2 oz. copper (0.0028″)

Figure 31. Junction Temperature Rise, TO-220

Circuit Data for Temperature Rise Curve

TO-263 Package (S)

Capacitors Surface mount tantalum, molded “D” size

Inductor Surface mount, Pulse Engineering, 68 μH

Diode Surface mount, 5A 40V, Schottky

PC board 9 square inches single sided 2 oz. copper (0.0028″)

Figure 32. Junction Temperature Rise, TO-263

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LM2596

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SNVS124C –NOVEMBER 1999–REVISED APRIL 2013

Figure 33. Delayed Startup

Figure 34. Undervoltage Lockout

for Buck Regulator

DELAYED STARTUP

The circuit in Figure 33 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 R2pulls the ON

/OFF pin low, thus allowing the circuit to start switching. Resistor R1is 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 34, while Figure 35 and Figure 36

applies the same feature to an inverting circuit. The circuit in Figure 35 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 36

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 kΩresistor

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 37 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.

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This circuit has an ON/OFF threshold of approximately 13V.

Figure 35. Undervoltage Lockout

for Inverting Regulator

This example uses the LM2596-5.0 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 38 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 LM2596 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.

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 36. Undervoltage Lockout with Hysteresis for Inverting Regulator

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LM2596

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SNVS124C –NOVEMBER 1999–REVISED APRIL 2013

CIN —68 μF/25V Tant. Sprague 595D

470 μF/50V Elec. Panasonic HFQ

COUT —47 μF/20V Tant. Sprague 595D

220 μF/25V Elec. Panasonic HFQ

Figure 37. Inverting −5V Regulator with Delayed Startup

Figure 38. 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 33 μH, 3.5A inductor is the best choice. Capacitor

selection can also be narrowed down to just a few values. Using the values shown in Figure 37 will provide good

results in the majority of inverting designs.

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 LM2596 current limit (approx 4.5A) 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, R1and R2) shown in Figure 37 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 39

and Figure 40.

Product Folder Links: LM2596

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SNVS124C –NOVEMBER 1999–REVISED APRIL 2013

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Figure 39. Inverting Regulator Ground Referenced Shutdown

Figure 40. Inverting Regulator Ground Referenced Shutdown using Opto Device

TYPICAL THROUGH HOLE PC BOARD LAYOUT, FIXED OUTPUT (1X SIZE), DOUBLE SIDED

CIN—470 μF, 50V, Aluminum Electrolytic Panasonic, “HFQ Series”

COUT—330 μF, 35V, Aluminum Electrolytic Panasonic, “HFQ Series”

D1—5A, 40V Schottky Rectifier, 1N5825

L1—47 μH, L39, Renco, Through Hole

Thermalloy Heat Sink #7020

Product Folder Links: LM2596

LM2596

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SNVS124C –NOVEMBER 1999–REVISED APRIL 2013

TYPICAL THROUGH HOLE PC BOARD LAYOUT, ADJUSTABLE OUTPUT (1X SIZE), DOUBLE SIDED

CIN—470 μF, 50V, Aluminum Electrolytic Panasonic, “HFQ Series”

COUT—220 μF, 35V Aluminum Electrolytic Panasonic, “HFQ Series”

D1—5A, 40V Schottky Rectifier, 1N5825

L1—47 μH, L39, Renco, Through Hole

R1—1 kΩ, 1%

R2—Use formula in Design Procedure

CFF—See Table 2.

Thermalloy Heat Sink #7020

Figure 41. PC Board Layout

Product Folder Links: LM2596

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SNVS124C –NOVEMBER 1999–REVISED APRIL 2013

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REVISION HISTORY

Changes from Revision B (April 2013) to Revision C Page

• Changed layout of National Data Sheet to TI format .......................................................................................................... 31

Product Folder Links: LM2596

PACKAGE OPTION ADDENDUM

www.ti.com 1-Nov-2013

Addendum-Page 1

PACKAGING INFORMATION

Orderable Device Status

(1)

Package Type Package

Drawing Pins Package

Qty Eco Plan

(2)

Lead/Ball Finish

(6)

MSL Peak Temp

(3)

Op Temp (°C) Device Marking

(4/5)

Samples

LM2596S-12/NOPB ACTIVE DDPAK/

TO-263 KTT 5 45 Pb-Free (RoHS

Exempt) CU SN Level-3-245C-168 HR LM2596S

-12 P+

LM2596S-3.3 NRND DDPAK/

TO-263 KTT 5 45 TBD Call TI Call TI LM2596S

-3.3 P+

LM2596S-3.3/NOPB ACTIVE DDPAK/

TO-263 KTT 5 45 Pb-Free (RoHS

Exempt) CU SN Level-3-245C-168 HR LM2596S

-3.3 P+

LM2596S-5.0 NRND DDPAK/

TO-263 KTT 5 45 TBD Call TI Call TI LM2596S

-5.0 P+

LM2596S-5.0/NOPB ACTIVE DDPAK/

TO-263 KTT 5 45 Pb-Free (RoHS

Exempt) CU SN Level-3-245C-168 HR LM2596S

-5.0 P+

LM2596S-ADJ/NOPB ACTIVE DDPAK/

TO-263 KTT 5 45 Pb-Free (RoHS

Exempt) CU SN Level-3-245C-168 HR -40 to 125 LM2596S

-ADJ P+

LM2596SX-12/NOPB ACTIVE DDPAK/

TO-263 KTT 5 500 Pb-Free (RoHS

Exempt) CU SN Level-3-245C-168 HR LM2596S

-12 P+

LM2596SX-3.3 NRND DDPAK/

TO-263 KTT 5 500 TBD Call TI Call TI LM2596S

-3.3 P+

LM2596SX-3.3/NOPB ACTIVE DDPAK/

TO-263 KTT 5 500 Pb-Free (RoHS

Exempt) CU SN Level-3-245C-168 HR LM2596S

-3.3 P+

LM2596SX-5.0/NOPB ACTIVE DDPAK/

TO-263 KTT 5 500 Pb-Free (RoHS

Exempt) CU SN Level-3-245C-168 HR LM2596S

-5.0 P+

LM2596SX-ADJ NRND DDPAK/

TO-263 KTT 5 500 TBD Call TI Call TI -40 to 125 LM2596S

-ADJ P+

LM2596SX-ADJ/NOPB ACTIVE DDPAK/

TO-263 KTT 5 500 Pb-Free (RoHS

Exempt) CU SN Level-3-245C-168 HR -40 to 125 LM2596S

-ADJ P+

LM2596T-12 NRND TO-220 NDH 5 45 TBD Call TI Call TI LM2596T

-12 P+

LM2596T-12/LF03 ACTIVE TO-220 NDH 5 45 Green (RoHS

& no Sb/Br) CU SN Level-1-NA-UNLIM LM2596T

-12 P+

LM2596T-12/NOPB ACTIVE TO-220 NDH 5 45 Green (RoHS

& no Sb/Br) CU SN Level-1-NA-UNLIM LM2596T

-12 P+

LM2596T-3.3 NRND TO-220 NDH 5 45 TBD Call TI Call TI LM2596T

-3.3 P+

LM2596T-3.3/LF03 ACTIVE TO-220 NDH 5 45 Green (RoHS

& no Sb/Br) CU SN Level-1-NA-UNLIM LM2596T

-3.3 P+

PACKAGE OPTION ADDENDUM

www.ti.com 1-Nov-2013

Addendum-Page 2

Orderable Device Status

(1)

Package Type Package

Drawing Pins Package

Qty Eco Plan

(2)

Lead/Ball Finish

(6)

MSL Peak Temp

(3)

Op Temp (°C) Device Marking

(4/5)

Samples

LM2596T-3.3/NOPB ACTIVE TO-220 NDH 5 45 Green (RoHS

& no Sb/Br) CU SN Level-1-NA-UNLIM LM2596T

-3.3 P+

LM2596T-5.0 NRND TO-220 NDH 5 45 TBD Call TI Call TI LM2596T

-5.0 P+

LM2596T-5.0/LF03 ACTIVE TO-220 NDH 5 45 Green (RoHS

& no Sb/Br) CU SN Level-1-NA-UNLIM LM2596T

-5.0 P+

LM2596T-5.0/NOPB ACTIVE TO-220 NDH 5 45 Green (RoHS

& no Sb/Br) CU SN Level-1-NA-UNLIM LM2596T

-5.0 P+

LM2596T-ADJ NRND TO-220 NDH 5 45 TBD Call TI Call TI -40 to 125 LM2596T

-ADJ P+

LM2596T-ADJ/LB05 NRND TO-220 NEB 5 45 TBD Call TI Call TI LM2596T

-ADJ P+

LM2596T-ADJ/LF02 ACTIVE TO-220 NEB 5 45 Green (RoHS

& no Sb/Br) CU SN Level-1-NA-UNLIM LM2596T

-ADJ P+

LM2596T-ADJ/NOPB ACTIVE TO-220 NDH 5 45 Green (RoHS

& no Sb/Br) CU SN Level-1-NA-UNLIM -40 to 125 LM2596T

-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.

(4) There may be additional marking, which relates to the logo, the lot trace code information, or the environmental category on the device.

PACKAGE OPTION ADDENDUM

www.ti.com 1-Nov-2013

Addendum-Page 3

(5) Multiple Device Markings will be inside parentheses. Only one Device 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 Device Marking for that device.

(6) Lead/Ball Finish - Orderable Devices may have multiple material finish options. Finish options are separated by a vertical ruled line. Lead/Ball Finish values may wrap to two lines if the finish

value exceeds the maximum column width.

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.

TAPE AND REEL INFORMATION

*All dimensions are nominal

Device Package

Type Package

Drawing Pins SPQ Reel

Diameter

(mm)

Reel

Width

W1 (mm)

(mm) B0

(mm) K0

(mm) P1

(mm) W

(mm) Pin1

Quadrant

LM2596SX-12/NOPB DDPAK/

TO-263 KTT 5 500 330.0 24.4 10.75 14.85 5.0 16.0 24.0 Q2

LM2596SX-3.3 DDPAK/

TO-263 KTT 5 500 330.0 24.4 10.75 14.85 5.0 16.0 24.0 Q2

LM2596SX-3.3/NOPB DDPAK/

TO-263 KTT 5 500 330.0 24.4 10.75 14.85 5.0 16.0 24.0 Q2

LM2596SX-5.0/NOPB DDPAK/

TO-263 KTT 5 500 330.0 24.4 10.75 14.85 5.0 16.0 24.0 Q2

LM2596SX-ADJ DDPAK/

TO-263 KTT 5 500 330.0 24.4 10.75 14.85 5.0 16.0 24.0 Q2

LM2596SX-ADJ/NOPB DDPAK/

TO-263 KTT 5 500 330.0 24.4 10.75 14.85 5.0 16.0 24.0 Q2

PACKAGE MATERIALS INFORMATION

www.ti.com 23-Sep-2013

Pack Materials-Page 1

*All dimensions are nominal

Device Package Type Package Drawing Pins SPQ Length (mm) Width (mm) Height (mm)

LM2596SX-12/NOPB DDPAK/TO-263 KTT 5 500 367.0 367.0 45.0

LM2596SX-3.3 DDPAK/TO-263 KTT 5 500 367.0 367.0 45.0

LM2596SX-3.3/NOPB DDPAK/TO-263 KTT 5 500 367.0 367.0 45.0

LM2596SX-5.0/NOPB DDPAK/TO-263 KTT 5 500 367.0 367.0 45.0

LM2596SX-ADJ DDPAK/TO-263 KTT 5 500 367.0 367.0 45.0

LM2596SX-ADJ/NOPB DDPAK/TO-263 KTT 5 500 367.0 367.0 45.0

PACKAGE MATERIALS INFORMATION

www.ti.com 23-Sep-2013

Pack Materials-Page 2

MECHANICAL DATA

NDH0005D

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MECHANICAL DATA

KTT0005B

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BOTTOM SIDE OF PACKAGE

TS5B (Rev D)

MECHANICAL DATA

NEB0005B

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MECHANICAL DATA

NEB0005E

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TI has specifically designated certain components as meeting ISO/TS16949 requirements, mainly for automotive use. In any case of use of

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