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SNVS124E –NOVEMBER 1999–REVISED FEBRUARY 2020

LM2596 SIMPLE SWITCHER®Power Converter 150-kHz

3-A Step-Down Voltage Regulator

LM2596

1 Features

• New product available: LMR33630 36-V, 3-A, 400-

kHz synchronous converter

• 3.3-V, 5-V, 12-V, and adjustable output versions

• Adjustable version output voltage range: 1.2-V to 37-V ±4% maximum over line and load conditions

• Available in TO-220 and TO-263 packages

• 3-A output load current

• Input voltage range up to 40 V

• Requires only four external components

• Excellent line and load regulation specifications

• 150-kHz Fixed-frequency internal oscillator

• TTL shutdown capability

• Low power standby mode, IQ, typically 80 μA

• High efficiency

• Uses readily available standard inductors

• Thermal shutdown and current-limit protection

• Create a custom design using the LM2596 with the WEBENCH Power Designer

2 Applications

• Appliances

• Grid infrastructure

• EPOS

• Home theater

3 Description

The LM2596 series of regulators are monolithic integrated circuits that provide all the active functions for a step-down (buck) switching regulator, capable of driving a 3-A load with excellent line and load regulation. These devices are available in fixed output voltages of 3.3 V, 5 V, 12 V, and an adjustable output version.

Requiring a minimum number of external components, these regulators are simple to use and include internal frequency compensation, and a fixedfrequency oscillator.

The LM2596 series operates at a switching frequency of 150 kHz, thus allowing smaller sized filter components than what would be required with lower frequency switching regulators. Available in a standard 5-pin TO-220 package with several different lead bend options, and a 5-pin TO-263 surface mount package.

The new product, LMR33630, offers reduced BOM cost, higher efficiency, and an 85% reduction in solution size among many other features. See the

device comparison table to compare specs. Start WEBENCH Design with LMR33630.

Device Information

PART NUMBER PACKAGE BODY SIZE (NOM)

LM2596

(1) For all available packages, see the orderable addendum at

the end of the data sheet.

TO-220 (5) 14.986 mm × 10.16 mm TO-263 (5) 10.10 mm × 8.89 mm

(1)

Typical Application

(Fixed Output Voltage Versions)

An IMPORTANT NOTICE at the end of this data sheet addresses availability, warranty, changes, use in safety-critical applications, intellectual property matters and other important disclaimers. PRODUCTION DATA.

LM2596

SNVS124E –NOVEMBER 1999–REVISED FEBRUARY 2020

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1 Features.................................................................. 1

2 Applications ........................................................... 1

3 Description ............................................................. 1

4 Revision History..................................................... 2

5 Description (continued)......................................... 3

6 Pin Configuration and Functions......................... 4

7 Specifications......................................................... 5

7.1 Absolute Maximum Ratings ..................................... 5

7.2 ESD Ratings.............................................................. 5

7.3 Operating Conditions ................................................ 5

7.4 Thermal Information.................................................. 5

7.5 Electrical Characteristics – 3.3-V Version................. 6

7.6 Electrical Characteristics – 5-V Version.................... 6

7.7 Electrical Characteristics – 12-V Version.................. 6

7.8 Electrical Characteristics – Adjustable Voltage

Version....................................................................... 6

7.9 Electrical Characteristics – All Output Voltage

Versions..................................................................... 7

7.10 Typical Characteristics............................................ 8

8 Detailed Description............................................ 11

8.1 Overview ................................................................. 11

8.2 Functional Block Diagram ....................................... 11

8.3 Feature Description................................................. 11

8.4 Device Functional Modes........................................ 15

9 Application and Implementation ........................ 16

9.1 Application Information............................................ 16

9.2 Typical Applications ................................................ 23

10 Power Supply Recommendations ..................... 32

11 Layout................................................................... 32

11.1 Layout Guidelines ................................................. 32

11.2 Layout Examples................................................... 32

11.3 Thermal Considerations........................................ 34

12 Device and Documentation Support ................. 36

12.1 Device Support...................................................... 36

12.2 Receiving Notification of Documentation Updates 36

12.3 Support Resources ............................................... 36

12.4 Trademarks........................................................... 36

12.5 Electrostatic Discharge Caution............................ 36

12.6 Glossary................................................................ 36

13 Mechanical, Packaging, and Orderable

Information........................................................... 36

4 Revision History

NOTE: Page numbers for previous revisions may differ from page numbers in the current version.

Changes from Revision D (May 2016) to Revision E Page

• Added link to the LMR33630 product folder in the Features ................................................................................................. 1

• Updated Description to include the LMR33630 product page, device comparison table, and WEBENCH link .................... 1

• Changed the package from 7 pins to 5 pins .......................................................................................................................... 1

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

• Added ESD Ratings table, Feature Description section, Device Functional Modes, Application and Implementation section, Power Supply Recommendations section, Layout section, Device and Documentation Support section, and

Mechanical, Packaging, and Orderable Information section.................................................................................................. 1

• Removed all references to design software Switchers Made Simple .................................................................................... 1

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

• Changed layout of National Semiconductor Data Sheet to TI format .................................................................................. 11

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SNVS124E –NOVEMBER 1999–REVISED FEBRUARY 2020

5 Description (continued)

A standard series of inductors are available from several different manufacturers optimized for use with the LM2596 series. This feature greatly simplifies the design of switch-mode power supplies.

Other features include a ±4% tolerance on output voltage under specified input voltage and output load conditions, and ±15% on the oscillator frequency. External shutdown is included, featuring typically 80 μA standby current. Self-protection features include a two stage frequency reducing current limit for the output switch and an overtemperature shutdown for complete protection under fault conditions.

Product Folder Links: LM2596

LM2596

SNVS124E –NOVEMBER 1999–REVISED FEBRUARY 2020

6 Pin Configuration and Functions

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NDH Package

5-Pin TO-220

Top View

KTT Package

5-Pin TO-263

Top View

Pin Functions

NO. NAME

1 V

2 Output O

3 Ground — Circuit ground 4 Feedback I Senses the regulated output voltage to complete the feedback loop.

5 ON/OFF I

I/O DESCRIPTION

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 required by the regulator.

Internal switch. The voltage at this pin switches between approximately (+VIN− V approximately −0.5 V, with a duty cycle of V circuitry, the PCB copper area connected to this pin must be kept to a minimum.

Allows the switching regulator circuit to be shut down using logic signals thus dropping the total input supply current to approximately 80 µA. Pulling this pin below a threshold voltage of approximately 1.3 V turns the regulator on, and pulling this pin above 1.3 V (up to a maximum of 25 V) shuts the regulator down. If this shutdown feature is not required, 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.

/ VIN. To minimize coupling to sensitive

OUT

SAT

) and

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SNVS124E –NOVEMBER 1999–REVISED FEBRUARY 2020

7 Specifications

7.1 Absolute Maximum Ratings

over operating free-air temperature range (unless otherwise noted)

Maximum supply voltage (VIN) 45 V SD/SS pin input voltage Delay pin voltage Flag pin voltage –0.3 45 V Feedback pin voltage –0.3 25 V Output voltage to ground, steady-state –1 V Power dissipation Internally limited

Lead temperature

Maximum junction temperature 150 °C Storage temperature, T

(1) Stresses beyond those listed under Absolute Maximum Ratings may cause permanent damage to the device. These are stress ratings

only, which do not imply functional operation of the device at these or any other conditions beyond those indicated under Recommended Operating Conditions. Exposure to absolute-maximum-rated conditions for extended periods may affect device reliability.

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

specifications.

(3) Voltage internally clamped. If clamp voltage is exceeded, limit current to a maximum of 1 mA.

(3)

KTW package

NDZ package, soldering (10 s) 260

stg

(1)(2)

MIN MAX UNIT

6 V

1.5 V

Vapor phase (60 s) 215

°CInfrared (10 s) 245

–65 150 °C

7.2 ESD Ratings

VALUE UNIT

(ESD)

Electrostatic discharge Human-body model (HBM), per ANSI/ESDA/JEDEC JS-001

(1)

±2000 V

(1) JEDEC document JEP155 states that 500-V HBM allows safe manufacturing with a standard ESD control process.

7.3 Operating Conditions

MIN MAX UNIT

Supply voltage 4.5 40 V Temperature –40 125 °C

7.4 Thermal Information

LM2596

— 50 50 — 30 — 20 —

UNITKTW (TO-263) NDZ (TO-220)

°C/W

θJA

θJC(top)

THERMAL METRIC

Junction-to-ambient thermal resistance

Junction-to-case (top) thermal resistance 2 2 °C/W

(2)(3)

(1)

5 PINS 5 PINS

See See See See

(4) (5) (6) (7)

(1) For more information about traditional and new thermal metrics, see the Semiconductor and IC Package Thermal Metrics application

report.

(2) The package thermal impedance is calculated in accordance to JESD 51-7. (3) Thermal Resistances were simulated on a 4-layer, JEDEC board. (4) Junction to ambient thermal resistance (no external heat sink) for the package mounted TO-220 package mounted vertically, with the

leads soldered to a printed circuit board with (1 oz.) copper area of approximately 1 in2. (5) Junction to ambient thermal resistance with the TO-263 package tab soldered to a single sided printed circuit board with 0.5 in2of 1-oz

copper area. (6) 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. (7) 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 PCB.

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7.5 Electrical Characteristics – 3.3-V Version

Specifications are for TJ= 25°C (unless otherwise noted)

PARAMETER TEST CONDITIONS MIN

SYSTEM PARAMETERS

OUT

Output voltage

η Efficiency VIN= 12 V, I

(1) 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). (2) Typical numbers are at 25°C and represent the most likely norm. (3) External components such as the catch diode, inductor, input and output capacitors can affect switching regulator system performance.

When the LM2596 is used as shown in Figure 35, system performance is shown in the test conditions column.

(3)

(see Figure 35 for test circuit)

4.75 V ≤ VIN≤ 40 V,

0.2 A ≤ I

LOAD

≤ 3 A

LOAD

TJ= 25°C 3.168 3.3 3.432 –40°C ≤ TJ≤ 125°C 3.135 3.465

= 3 A 73%

(1)

TYP

(2)

MAX

(1)

UNIT

7.6 Electrical Characteristics – 5-V Version

Specifications are for TJ= 25°C (unless otherwise noted)

PARAMETER TEST CONDITIONS MIN

SYSTEM PARAMETERS

OUT

Output voltage

η Efficiency VIN= 12 V, I

(1) All room temperature limits are 100% production tested. All limits at temperature extremes are specified via correlation using standard

When the LM2596 is used as shown in Figure 35, system performance is shown in the test conditions column.

(3)

(see Figure 35 for test circuit)

7 V ≤ VIN≤ 40 V,

0.2 A ≤ I

LOAD

≤ 3 A

LOAD

TJ= 25°C 4.8 5 5.2 –40°C ≤ TJ≤ 125°C 4.75 5.25

= 3 A 80%

(1)

TYP

(2)

MAX

(1)

UNIT

7.7 Electrical Characteristics – 12-V Version

Specifications are for TJ= 25°C (unless otherwise noted)

PARAMETER TEST CONDITIONS MIN

SYSTEM PARAMETERS

OUT

Output voltage

η Efficiency VIN= 25 V, I

(1) All room temperature limits are 100% production tested. All limits at temperature extremes are specified via correlation using standard

When the LM2596 is used as shown in Figure 35, system performance is shown in the test conditions column.

(3)

(see Figure 35 for test circuit)

15 V ≤ VIN≤ 40 V,

0.2 A ≤ I

LOAD

≤ 3 A

LOAD

TJ= 25°C 11.52 12 12.48 –40°C ≤ TJ≤ 125°C 11.4 12.6

= 3 A 90%

(1)

TYP

(2)

MAX

(1)

UNIT

7.8 Electrical Characteristics – Adjustable Voltage Version

Specifications are for TJ= 25°C (unless otherwise noted)

PARAMETER TEST CONDITIONS MIN

SYSTEM PARAMETERS

Feedback voltage

η Efficiency VIN= 12 V, V

(1) All room temperature limits are 100% production tested. All limits at temperature extremes are specified via correlation using standard

When the LM2596 is used as shown in Figure 35, system performance is shown in the test conditions column.

(3)

(see Figure 35 for test circuit)

4.5 V ≤ VIN≤ 40 V, 0.2 A ≤ I V

programmed for 3 V

OUT

(see Figure 35 for test circuit)

OUT

= 3 V, I

≤ 3 A 1.23

LOAD

TJ= 25°C 1.193 1.267 –40°C ≤ TJ≤ 125°C 1.18 1.28

= 3 A 73%

LOAD

(1)

TYP

(2)

MAX

(1)

UNIT

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SNVS124E –NOVEMBER 1999–REVISED FEBRUARY 2020

7.9 Electrical Characteristics – All Output Voltage Versions

Specifications are for TJ= 25°C, I 12-V version (unless otherwise noted).

PARAMETER TEST CONDITIONS MIN

DEVICE PARAMETERS

SHUTDOWN/SOFT-START CONTROL (see Figure 35 for test circuit)

I I

(1) All room temperature limits are 100% production tested. All limits at temperature extremes are specified via correlation using standard (2) Typical numbers are at 25°C and represent the most likely norm.

(3) The switching frequency is reduced when the second stage current limit is activated. The amount of reduction is determined by the (4) No diode, inductor, or capacitor connected to output pin.

(5) Feedback pin removed from output and connected to 0 V to force the output transistor switch ON. (6) Feedback pin removed from output and connected to 12 V for the 3.3-V, 5-V, and the adjustable versions, and 15 V for the 12-V

(7) VIN= 40 V.

Feedback bias current

Oscillator frequency

Saturation voltage

SAT

Max duty cycle (ON) Min duty cycle (OFF)

Current limit

Output leakage

current Operating quiescent

current Current standby

STBY

quiescent

ON/OFF pin logic input

(4) (6)

(6)

(3)

(4) (5)

(5)

(6)

(4) (5)

threshold voltage

ON/OFF pin input current

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

severity of current overload.

version, to force the output transistor switch OFF.

= 500 mA, VIN= 12 V for the 3.3-V, 5-V, and adjustable version, and VIN= 24 V for the

LOAD

(1)

Adjustable version only, VFB= 1.3 V

TJ= 25°C 10 50

–40°C ≤ TJ≤ 125°C 100 TJ= 25°C 127 150 173 –40°C ≤ TJ≤ 125°C 110 173

OUT

= 3 A

TJ= 25°C 1.16 1.4

–40°C ≤ TJ≤ 125°C 1.5

TYP

(2)

MAX

(1)

UNIT

kHz

100%

Peak current

TJ= 25°C 3.6 4.5 6.9

–40°C ≤ TJ≤ 125°C 3.4 7.5 Output = 0 V, VIN= 40 V 50 μA Output = –1 V 2 30 mA

(6)

See

TJ= 25°C 80 200 μA ON/OFF pin = 5 V (OFF)

Low (regulator ON)

High (regulator OFF)

= 2.5 V (regulator OFF) 5 15 μA

LOGIC

= 0.5 V (regulator ON) 0.02 5 μA

LOGIC

(7)

–40°C ≤ TJ≤ 125°C 250 μA

TJ= 25°C 1.3

–40°C ≤ TJ≤ 125°C 0.6

TJ= 25°C 1.3

–40°C ≤ TJ≤ 125°C 2

5 10 mA

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LM2596

SNVS124E –NOVEMBER 1999–REVISED FEBRUARY 2020

7.10 Typical Characteristics

See Figure 35 for test circuit

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Figure 1. Normalized Output Voltage

Figure 3. Efficiency

Figure 2. Line Regulation

Figure 4. Switch Saturation Voltage

Figure 5. Switch Current Limit Figure 6. Dropout Voltage

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Typical Characteristics (continued)

See Figure 35 for test circuit

Figure 7. Operating Quiescent Current Figure 8. Shutdown Quiescent Current

LM2596

SNVS124E –NOVEMBER 1999–REVISED FEBRUARY 2020

Figure 9. Minimum Operating Supply Voltage Figure 10. ON/OFF Threshold Voltage

Figure 11. ON/OFF Pin Current (Sinking)

Figure 12. Switching Frequency

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Typical Characteristics (continued)

See Figure 35 for test circuit

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Figure 13. Feedback Pin Bias Current

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8 Detailed Description

8.1 Overview

The LM2596 SIMPLE SWITCHER®regulator is an easy-to-use, nonsynchronous, step-down DC-DC converter with a wide input voltage range up to 40 V. The regulator is capable of delivering up to 3-A DC load current with excellent line and load regulation. These devices are available in fixed output voltages of 3.3-V, 5-V, 12-V, and an adjustable output version. The family requires few external components, and the pin arrangement was designed for simple, optimum PCB layout.

8.2 Functional Block Diagram

8.3 Feature Description

8.3.1 Delayed Start-Up

The circuit in Figure 14 uses 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, 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 25 V), 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 start-up 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.

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Feature Description (continued)

Figure 14. Delayed Start-Up

8.3.2 Undervoltage Lockout

Some applications require the regulator to remain off until the input voltage reaches a predetermined voltage.

Figure 15 shows an undervoltage lockout feature applied to a buck regulator, while Figure 16 and Figure 17

apply the same feature to an inverting circuit. The circuit in Figure 16 features a constant threshold voltage for turnon and turnoff (Zener voltage plus approximately one volt). If hysteresis is required, the circuit in Figure 17 has a turnon voltage which is different than the turnoff voltage. The amount of hysteresis is approximately equal to the value of the output voltage. If Zener voltages greater than 25 V are used, an additional 47-kΩ resistor is required from the ON/OFF pin to the ground pin to stay within the 25 V maximum limit of the ON/OFF pin.

Figure 15. Undervoltage Lockout

for Buck Regulator

8.3.3 Inverting Regulator

The circuit in Figure 18 converts a positive input voltage to a negative output voltage with a common ground. The circuit operates by bootstrapping the ground pin of the regulator 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 13 V.

Figure 16. Undervoltage Lockout

for Inverting Regulator

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Feature Description (continued)

This example uses the LM2596-5.0 to generate a −5-V output, but other output voltages are possible by selecting other output voltage versions, including the adjustable version. Because 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. Figure 19 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 40 V. For example, when converting +20 V to −12 V, the regulator would see 32 V between the input pin and ground pin. The LM2596 has a maximum input voltage spec of 40 V.

Additional diodes are required in this regulator configuration. Diode D1 is used to isolate input voltage ripple or noise from coupling through the CINcapacitor to the output, under light or no load conditions. Also, this diode isolation changes the topology to closely resemble a buck configuration, thus providing good closed-loop stability. TI recommends using a Schottky diode 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 CINcan 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= 13 V Regulator stops switching at VIN= 8 V

Figure 17. Undervoltage Lockout With Hysteresis for Inverting Regulator

CIN— 68-μF, 25-V Tant. Sprague 595D

470 -μF, 50-V Elec. Panasonic HFQ

— 47-μF, 20-V Tant. Sprague 595D

OUT

220-μF, 25-V Elec. Panasonic HFQ

Figure 18. Inverting −5-V Regulator With Delayed Start-Up

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Feature Description (continued)

Figure 19. 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, 3.5-A inductor is the best choice. Capacitor selection can also be narrowed down to just a few values. Using the values shown in Figure 18 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 (approximately 4.5 A) are required 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 start-up currents required by the inverting topology, the delayed start-up feature (C1, R1, and R2) shown in Figure 18 is recommended. By delaying the regulator start-up, the input capacitor is allowed to charge up to a higher voltage before the switcher begins operating. A portion of the high input current required for start-up is now supplied by the input capacitor (CIN). For severe start-up conditions, the input capacitor can be made much larger than normal.

8.3.4 Inverting Regulator Shutdown Methods

Using the ON/OFF pin in a standard buck configuration is simple. To turn the regulator ON, pull the ON/OFF pin below 1.3 V (at 25°C, referenced to ground). To turn the regulator OFF, pull the ON/OFF pin above 1.3 V. 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 20 and Figure 21.

Figure 20. Inverting Regulator Ground Referenced Shutdown

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Feature Description (continued)

Figure 21. Inverting Regulator Ground Referenced Shutdown Using Opto Device

8.4 Device Functional Modes

8.4.1 Discontinuous Mode Operation

The selection guide chooses inductor values suitable for continuous mode operation, but for low current applications or high input voltages, a discontinuous mode design can be a better choice. A discontinuous mode design would use an inductor that would be physically smaller, and would require only one half to one third the inductance value required for a continuous mode design. The peak switch and inductor currents will be higher in a discontinuous design, but at these low load currents (1 A and below), the maximum switch current will still be less than the switch current limit.

Discontinuous operation can have voltage waveforms that are considerably different than a continuous design. The output pin (switch) waveform can have some damped sinusoidal ringing present (see Figure 36). 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 nor 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 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.

Figure 22. Post Ripple Filter Waveform

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9 Application and Implementation

NOTE

Information in the following applications sections is not part of the TI component specification, and TI does not warrant its accuracy or completeness. TI’s customers are responsible for determining suitability of components for their purposes. Customers should validate and test their design implementation to confirm system functionality.

9.1 Application Information

9.1.1 Input Capacitor (CIN)

A low ESR aluminum or tantalum bypass capacitor is required between the input pin and ground pin. It must be placed near the regulator using short leads. This capacitor prevents large voltage transients from occuring at the input, and provides the instantaneous current required 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 input capacitor of the buck converter, this capacitor must 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 power rating of the capacitor. 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. For a given capacitor value, a higher voltage electrolytic capacitor is 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 required to satisfy the RMS current requirements.

Figure 23 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.

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 turnon 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 turnon 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.

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SNVS124E –NOVEMBER 1999–REVISED FEBRUARY 2020

Application Information (continued)

9.1.2 Feedforward Capacitor (CFF)

NOTE

For adjustable output voltage version only.

A feedforward capacitor, shown across R2 in Table 6, is used when the output voltage is greater than 10 V or when C phase margin for better loop stability. For CFFselection, see the Detailed Design Procedure section.

has a very low ESR. This capacitor adds lead compensation to the feedback loop and increases the

OUT

Figure 23. RMS Current Ratings for Low ESR Electrolytic Capacitors (Typical)

9.1.3 Output Capacitor (C

OUT

)

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 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 required. 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, see Output Voltage Ripple and Transients for a post ripple filter.

An ESR value of the aluminum electrolytic capacitor is related to the capacitance value and its voltage rating. In most cases, higher voltage electrolytic capacitors have lower ESR values (see Figure 24). Often, capacitors with much higher voltage ratings may be required 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 Table 3 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 is typically three times as large at −25°C and as much as 10 times as large at −40°C. See

Figure 25.

Solid tantalum capacitors have a much better ESR specifications for cold temperatures and are recommended for temperatures below −25°C.

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Application Information (continued)

Figure 24. Capacitor ESR versus Capacitor Voltage Rating (Typical Low-ESR Electrolytic Capacitor)

9.1.4 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 placed 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 (5 V 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 25. Capacitor ESR Change versus Temperature

9.1.5 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.

In many cases the preferred mode of operation is the continuous mode, which offers greater output power, lower peak switch, lower inductor and diode currents, and can have lower output ripple voltage. However, the continuous mode does require larger inductor values to keep the inductor current flowing continuously, especially at low output load currents or high input voltages.

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Application Information (continued)

To simplify the inductor selection process, an inductor selection guide (nomograph) was designed (see Figure 27 through Figure 30). 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 26.)

Figure 26. (ΔI

) Peak-to-Peak Inductor

IND

Ripple Current (as a Percentage of the Load Current)

versus 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, and so forth, 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 because 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 (see Open-Core Inductors).

When multiple switching regulators are located on the same PCB, 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 Schottky, ferrite bobbin core for Renco and Coilcraft, and powdered iron toroid for Pulse Engineering.

Exceeding the maximum current rating of the inductor can 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 or the LM2596. Different inductor types have different saturation characteristics, so consider this when selecting an inductor.

The inductor manufacturer's data sheets include current and energy limits to avoid inductor saturation. For continuous mode operation, see the inductor selection graphs in Figure 27 through Figure 30.

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Application Information (continued)

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Figure 27. LM2596-3.3

Figure 29. LM2596-12

Figure 28. LM2596-5.0

Figure 30. LM2596-ADJ

Table 1. Inductor Manufacturers Part Numbers

INDUCTANCE

(μH)

L15

22 0.99 67148350 67148460

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

L25

15 2.10 67148380 67148490

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

CURRENT

(A)

SCHOTT RENCO PULSE ENGINEERING COILCRAFT

THROUGH-

HOLE

SURFACE-

MOUNT

THROUGH-

HOLE

RL-1284-22-

RL-1283-22-

RL-1283-15-

SURFACE-

MOUNT

RL1500-22 PE-53815 PE-53815-S DO3308-223

— PE-53824 PE-53825-S DO3316-223

— PE-53825 PE-53824-S DO3316-153

THROUGH-

HOLE

SURFACE-

MOUNT

SURFACE-

MOUNT

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Application Information (continued)

Table 1. Inductor Manufacturers Part Numbers (continued)

INDUCTANCE

(μH)

L32 33 2.50 67144160 67144540 RL-5471-7 — PE-53932 PE-53932-S DO5022P-333 L33

22 3.10 67148390 67148500

L34

15 3.40 67148400 67148790

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 —

9.1.6 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, exercise caution when using extremely low ESR capacitors because they can affect the loop stability, resulting in oscillation problems. TI recommends a post ripple filter if very low output ripple voltage is required (less than 20 mV) (see Figure 32). 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.

Figure 22 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, preferably 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, 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 reaches zero, and the switcher smoothly changes from a continuous to a discontinuous mode of operation. Most switcher designs (regardless of how large the inductor value is) is forced to run discontinuous if the output is lightly loaded. This is a perfectly acceptable mode of operation.

CURRENT

(A)

SCHOTT RENCO PULSE ENGINEERING COILCRAFT

THROUGH-

HOLE

SURFACE-

MOUNT

THROUGH-

HOLE

RL-1283-22-

RL-1283-15-

SURFACE-

MOUNT

— PE-53933 PE-53933-S DO5022P-223

— PE-53934 PE-53934-S DO5022P-153

THROUGH-

HOLE

SURFACE-

MOUNT

SURFACE-

MOUNT

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Figure 31. Peak-to-Peak Inductor

Ripple Current versus Load Current

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In a switching regulator design, knowing the value of the peak-to-peak inductor ripple current (ΔI

) can be

IND

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 ΔI

. When the inductor nomographs in Figure 27

IND

through Figure 30 are used to select an inductor value, the peak-to-peak inductor ripple current can immediately be determined. Figure 31 shows the range of (ΔI also shows how the peak-to-peak inductor ripple current (ΔI

) that can be expected for different load currents. Figure 31

IND

) changes as you go from the lower border to the

IND

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.

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:

= 5 V, maximum load current of 2.5 A

OUT

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

The selection guide in Figure 28 shows that the vertical line for a 2.5-A load current and the horizontal line for the 12-V input voltage intersect approximately midway between the upper and lower borders of the 33-μH inductance region. A 33-μH inductor allows a peak-to-peak inductor current (ΔI

), which is a percentage of the maximum

IND

load current, to flow. In Figure 31, follow the 2.5-A line approximately midway into the inductance region, and read the peak-to-peak inductor ripple current (ΔI

) on the left hand axis (approximately 620 mAp-p).

IND

As the input voltage increases to 16 V, approaching the upper border of the inductance region, the inductor ripple current increases. Figure 31 shows that for a load current of 2.5 A, the peak-to-peak inductor ripple current (ΔI

) is 620 mA with 12 VIN, and can range from 740 mA at the upper border (16 VIN) to 500 mA at the lower

IND

border (10 VIN). Once the ΔI

value is known, use these equations to calculate additional information about the switching

IND

regulator circuit.

1. Peak Inductor or peak switch current:

2. Minimum load current before the circuit becomes discontinuous:

3. Output Ripple Voltage = (ΔI

) × (ESR of C

IND

) = 0.62 A × 0.1 Ω = 62 mVp-p

OUT

4. added for line break

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9.1.7 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 PCB 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 PCB 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 is possible that the location of the inductor with respect to other PC traces can 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 can 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, placing 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). However, problems can arise if the trace is off center one direction or the other. 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 users, but to alert users on what kind of problems to watch out for. 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.

9.2 Typical Applications

9.2.1 LM2596 Fixed Output Series Buck Regulator

CIN— 470-μF, 50-V, Aluminum Electrolytic Nichicon PL Series C

— 220-μF, 25-V Aluminum Electrolytic, Nichicon PL Series

OUT

D1 — 5-A, 40-V Schottky Rectifier, 1N5825 L1 — 68 μH, L38

Figure 32. Fixed Output Voltage Version

9.2.1.1 Design Requirements

Table 2 lists the design parameters for this example.

Table 2. Design Parameters

PARAMETER EXAMPLE VALUE

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

Maximum DC Input Voltage, VIN(max) 12 V

Maximum Load Current, I

OUT

(max) 3 A

LOAD

5 V

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9.2.1.2 Detailed Design Procedure

9.2.1.2.1 Custom Design with WEBENCH Tools

Click here to create a custom design using the LM2596 device with the WEBENCH®Power Designer.

1. Start by entering your VIN, V

OUT

and I

requirements.

OUT

2. Optimize your design for key parameters like efficiency, footprint and cost using the optimizer dial and compare this design with other possible solutions from Texas Instruments.

3. WEBENCH Power Designer provides you with a customized schematic along with a list of materials with real time pricing and component availability.

4. In most cases, you will also be able to: – Run electrical simulations to see important waveforms and circuit performance, – Run thermal simulations to understand the thermal performance of your board, – Export your customized schematic and layout into popular CAD formats, – Print PDF reports for the design, and share your design with colleagues.

5. Get more information about WEBENCH tools at www.ti.com/webench.

9.2.1.2.2 Inductor Selection (L1)

1. Select the correct inductor value selection guide from Figure 27, Figure 28, or Figure 29 (output voltages of

3.3 V, 5 V, or 12 V respectively). Use the inductor selection guide for the 5-V version shown in Figure 28.

2. 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). From the inductor value selection guide shown in Figure 28, the inductance region intersected by the 12-V horizontal line and the 3-A vertical line is 33 μH, and the inductor code is L40.

3. Select an appropriate inductor from the four manufacturer's part numbers listed in Table 1. The inductance value required is 33 μH. See row L40 of Table 1 and choose an inductor part number from any of the manufacturers shown. In most instances, both through-hole and surface-mount inductors are available.

9.2.1.2.3 Output Capacitor Selection (C

OUT

)

1. In the majority of applications, low ESR (Equivalent Series Resistance) electrolytic capacitors between 82 μF and 820 μF and low ESR solid tantalum capacitors between 10 μF and 470 μF provide the best results. This capacitor must be placed close to the IC using short capacitor leads and short copper traces. Do not use capacitors larger than 820 μF .

NOTE

For additional information, see section on output capacitors in Table 3.

2. To simplify the capacitor selection procedure, see Table 3 for quick design component selection. 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.

From Table 3, locate the 5-V output voltage section. In the load current column, choose the load current line that is closest to the current required for the application; for this example, use the 3-A line. In the maximum input voltage column, select the line that covers the input voltage required for the application; in this example, use the 15-V line. The rest of the line shows recommended inductors and capacitors that will provide the best overall performance.

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Table 3. LM2596 Fixed Voltage Quick Design Component Selection Table

OUTPUT CAPACITOR

NICHICON PL SERIES

(μF/V)

AVX TPS

SERIES

(μF/V)

SPRAGUE

595D SERIES

(μF/V)

OUTPUT

VOLTAGE

(V)

3.3

CONDITIONS INDUCTOR

LOAD

CURRENT

(A)

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

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

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

MAX INPUT

VOLTAGE

(V)

INDUCTANCE

(μH)

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

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

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

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

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

INDUCTOR

(#)

THROUGH-HOLE ELECTROLYTIC SURFACE-MOUNT TANTALUM PANASONIC

HFQ SERIES

(μF/V)

The capacitor list contains both through-hole electrolytic and surface-mount tantalum capacitors from four different capacitor manufacturers. TI recommends that both the manufacturers and the manufacturer's series that are listed in Table 3.

In this example aluminum electrolytic capacitors from several different manufacturers are available with the range of ESR numbers required. – 330-μF, 35-V Panasonic HFQ Series – 330-μF, 35-V Nichicon PL Series

3. The capacitor voltage rating for electrolytic capacitors should be at least 1.5 times greater than the output voltage, and often require much higher voltage ratings to satisfy the low ESR requirements for low output ripple voltage.

For a 5-V output, a capacitor voltage rating of at least 7.5 V is required. But even a low ESR, switching grade, 220-μF, 10-V aluminum electrolytic capacitor would exhibit approximately 225 mΩ of ESR (see

Figure 24 for the ESR versus voltage rating). This amount of ESR would result in relatively high output ripple

voltage. To reduce the ripple to 1% or less of the output voltage, a capacitor with a higher value or with a higher voltage rating (lower ESR) must be selected. A 16-V or 25-V capacitor will reduce the ripple voltage by approximately half.

9.2.1.2.4 Catch Diode Selection (D1)

1. 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 must have a 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. See Table 4. In this example, a 5-A, 20-V, 1N5823 Schottky diode will provide the best performance, and will not be overstressed even for a shorted output.

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Table 4. Diode Selection Table

3-A DIODES 4-A TO 6-A DIODES

20 V

30 V

40 V SK34 SR304 50WQ04 SR504

50 V SK35 30WF10 SR305 50WF10 HER601

or MBRS360 MBR350 50WQ05 SB550

More 30WQ05 31DQ05 50SQ080

SURFACE-MOUNT THROUGH-HOLE SURFACE-MOUNT THROUGH-HOLE

SCHOTTKY

SK32 SR302 1N5823

30WQ03 1N5821 SK33 MBR330 50WQ03 SR503

MBRS340 MBR340 1N5825 30WQ04 MURS320 31DQ04 MUR320 MURS620 SB540 MUR620

ULTRA FAST

RECOVERY

All of

these

diodes

are rated to at least

50V.

SCHOTTKY

1N5820 All of

MBR320 SB520

31DQ03 1N5824 1N5822 SB530

ULTRA FAST

RECOVERY

these

diodes

are rated to at least

50V.

SCHOTTKY

ULTRA FAST

RECOVERY

All of

these

diodes

are rated to at least

50V.

SCHOTTKY

SR502 All of

ULTRA FAST

RECOVERY

these

diodes

are

rated to

at least

50V.

2. The reverse voltage rating of the diode must be at least 1.25 times the maximum input voltage.

3. This diode must be fast (short reverse recovery time) and must be placed 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 must be the first choice, especially in low output voltage applications. Ultra-fast recovery, or high-efficiency rectifiers also provide good results. Ultrafast recovery diodes typically have reverse recovery times of 50 ns or less. Rectifiers such as the 1N5400 series must not be used because they are too slow.

9.2.1.2.5 Input Capacitor (CIN)

A low ESR aluminum or tantalum bypass capacitor is required between the input pin and ground pin to prevent large voltage transients from appearing at the input. This capacitor must be placed 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. Figure 23 shows typical RMS current ratings for several different aluminum electrolytic capacitor values.

For an aluminum electrolytic, the capacitor voltage rating must be approximately 1.5 times the maximum input voltage. Exercise caution if solid tantalum capacitors are used (see Input Capacitor (CIN)). The tantalum capacitor voltage rating should be 2 times the maximum input voltage and TI recommends 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 V pin.

The important parameters for the Input capacitor are the input voltage rating and the RMS current rating. With a nominal input voltage of 12 V, an aluminum electrolytic capacitor with a voltage rating greater than 18 V (1.5 × VIN) is necessary. The next higher capacitor voltage rating is 25 V.

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 3-A load, a capacitor with a RMS current rating of at least 1.5 A is required.

Figure 23 can be used to select an appropriate input capacitor. From the curves, locate the 35-V line and note

which capacitor values have RMS current ratings greater than 1.5 A. A 680-μF, 35-V capacitor could be used. For a through-hole design, a 680-μF, 35-V 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 exercise caution with regard to the capacitor surge current rating (see Input Capacitor (CIN) in this data sheet). The TPS series available from AVX, and the 593D series from Sprague are both surge current tested.

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9.2.1.3 Application Curves

LM2596

SNVS124E –NOVEMBER 1999–REVISED FEBRUARY 2020

Continuous Mode Switching Waveforms VIN= 20 V, V I

= 2 A, L = 32 μH, C

LOAD

A: Output Pin Voltage, 10 V/div.

= 220 μF, C

OUT

ESR = 50 mΩ

OUT

B: Inductor Current 1 A/div. C: Output Ripple Voltage, 50 mV/div.

OUT

= 5 V,

Load Transient Response for Continuous Mode VIN= 20 V, V 5 V, I 50 mΩ A: Output Voltage, 100 mV/div. (AC) B: 500-mA to 2-A Load Pulse

Figure 33. Horizontal Time Base: 2 μs/div

9.2.2 LM2596 Adjustable Output Series Buck Regulator

where V

REF

= 1.23 V

= 500 mA to 2 A, L = 32 μH, C

LOAD

OUT

Figure 34. Horizontal Time Base: 100 μs/div

= 220 μF, C

OUT

ESR =

Select R1to be approximately 1 kΩ, use a 1% resistor for best stability. CIN— 470-μF, 50-V, Aluminum Electrolytic Nichicon PL Series C

— 220-μF, 35-V Aluminum Electrolytic, Nichicon PL Series

OUT

D1 — 5-A, 40-V Schottky Rectifier, 1N5825 L1 — 68 μH, L38 R1 — 1 kΩ, 1% CFF— See Feedforward Capacitor (CFF)

Figure 35. Adjustable Output Voltage Version

Product Folder Links: LM2596

LM2596

SNVS124E –NOVEMBER 1999–REVISED FEBRUARY 2020

www.ti.com

9.2.2.1 Design Requirements

Table 5 lists the design parameters for this example.

Table 5. Design Parameters

PARAMETER EXAMPLE VALUE

Regulated output voltage (3.3V, 5V or 12V), V

Maximum DC input voltage, VIN(max) 28 V

Maximum load current, I

Switching frequency, F Fixed at a nominal 150 kHz

(max) 3 A

LOAD

OUT

20 V

9.2.2.2 Detailed Design Procedure

9.2.2.2.1 Programming Output Voltage

Select R1and R2, as shown in Table 6 Use Equation 1 to select the appropriate resistor values.

(1)

Select a value for R1between 240 Ω and 1.5 kΩ. The lower resistor values minimize noise pickup in the sensitive feedback pin. (For the lowest temperature coefficient and the best stability with time, use 1% metal film resistors.). Calculate R2with Equation 2.

Select R1to be 1 kΩ, 1%. Solve for R2in Equation 3.

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

9.2.2.2.2 Inductor Selection (L1)

1. Calculate the inductor Volt • microsecond constant E × T (V × μs), with Equation 4:

where

• V

• VD= diode forward voltage drop = 0.5 V (4)

= internal switch saturation voltage = 1.16 V

SAT

Calculate the inductor Volt • microsecond constant (E × T),

2. 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 30.

E × T = 34.2 (V × μs)

3. On the horizontal axis, select the maximum load current. I

(max) = 3 A

LOAD

4. 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). From the inductor value selection guide shown in Figure 30, the inductance region intersected by the 34 (V • μs) horizontal line and the 3-A

(2)

(3)

(5)

Product Folder Links: LM2596

LM2596

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SNVS124E –NOVEMBER 1999–REVISED FEBRUARY 2020

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

5. Select an appropriate inductor from the manufacturers' part numbers listed in Table 1. From the table in

Table 1, locate line L39, and select an inductor part number from the list of manufacturers part numbers.

9.2.2.2.3 Output Capacitor Selection (C

OUT

)

1. In the majority of applications, low ESR electrolytic or solid tantalum capacitors between 82 μF and 820 μF provide the best results. This capacitor must be placed close to the IC using short capacitor leads and short copper traces. Do not use capacitors larger than 820 μF.

NOTE

For additional information, see section on output capacitors in Output Capacitor (C

OUT

)

section.

2. To simplify the capacitor selection procedure, see Table 6 for a quick design guide. This table contains different output voltages, and lists various output capacitors that will provide the best design solutions.

From Table 6, 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 24-V line. Under the Output Capacitor (C

OUT

section, select a capacitor from the list of through-hole electrolytic or surface-mount tantalum types from four different capacitor manufacturers. TI recommends that both the manufacturers and the manufacturers' series that are listed in Table 6 be used.

In this example, through hole aluminum electrolytic capacitors from several different manufacturers are available. – 220-μF, 35-V Panasonic HFQ Series – 150-μF, 35-V Nichicon PL Series

3. The capacitor voltage rating must be at least 1.5 times greater than the output voltage, and often much higher voltage ratings are required to satisfy the low ESR requirements required for low output ripple voltage.

For a 20-V output, a capacitor rating of at least 30 V is required. In this example, either a 35-V or 50-V capacitor would work. A 35-V rating was chosen, although a 50-V rating could also be used if a lower output ripple voltage is required.

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 Table 6. Refer to the capacitor manufacturers data sheet for this information.

)

9.2.2.2.4 Feedforward Capacitor (CFF)

See Table 6. For output voltages greater than approximately 10 V, an additional capacitor is required. The compensation

capacitor is typically between 100 pF and 33 nF, and is wired in parallel with the output voltage setting resistor, R2. It provides additional stability for high output voltages, low input or output voltages, or very low ESR output capacitors, such as solid tantalum capacitors. Calculate the value for CFFwith Equation 6:

(6)

This capacitor type can be ceramic, plastic, silver mica, and so forth. Because of the unstable characteristics of ceramic capacitors made with Z5U material, they are not recommended.

Table 6 contains feedforward capacitor values for various output voltages. In this example, a 560-pF capacitor is

required.

Table 6. Output Capacitor and Feedforward Capacitor Selection Table

OUTPUT

VOLTAGE

(V)

2 820/35 820/35 33 nF 330/6.3 470/4 33 nF 4 560/35 470/35 10 nF 330/6.3 390/6.3 10 nF

HFQ SERIES

THROUGH-HOLE OUTPUT CAPACITOR SURFACE-MOUNT OUTPUT CAPACITOR

PANASONIC

(μF/V)

NICHICON PL

SERIES

(μF/V)

FEEDFORWARD

CAPACITOR

Product Folder Links: LM2596

AVX TPS

SERIES

(μF/V)

SPRAGUE

595D SERIES

(μF/V)

FEEDFORWARD

CAPACITOR

LM2596

SNVS124E –NOVEMBER 1999–REVISED FEBRUARY 2020

www.ti.com

Table 6. Output Capacitor and Feedforward Capacitor Selection Table (continued)

OUTPUT

VOLTAGE

(V)

6 470/25 470/25 3.3 nF 220/10 330/10 3.3 nF

9 330/25 330/25 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

9.2.2.2.5 Catch Diode Selection (D1)

HFQ SERIES

THROUGH-HOLE OUTPUT CAPACITOR SURFACE-MOUNT OUTPUT CAPACITOR

PANASONIC

(μF/V)

NICHICON PL

SERIES

(μF/V)

FEEDFORWARD

CAPACITOR

AVX TPS

SERIES

(μF/V)

SPRAGUE

595D SERIES

(μF/V)

FEEDFORWARD

CAPACITOR

1. 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 must have a 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. See Table 4. Schottky diodes provide the best performance, and in this example, a 5-A, 40-V, 1N5825 Schottky diode would be a good choice. The 5-A diode rating is more than adequate and will not be overstressed even for a shorted output.

2. The reverse voltage rating of the diode must be at least 1.25 times the maximum input voltage.

3. This diode must be fast (short reverse recovery time) and must be placed 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 must be the first choice, especially in low output voltage applications. Ultra-fast recovery or high-efficiency rectifiers are also good choices, but some types with an abrupt turnoff 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 must not be used because they are too slow.

9.2.2.2.6 Input Capacitor (CIN)

A low ESR aluminum or tantalum bypass capacitor is required 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. Figure 23 shows typical RMS current ratings for several different aluminum electrolytic capacitor values.

This capacitor must be placed close to the IC using short leads and the voltage rating must be approximately 1.5 times the maximum input voltage.

If solid tantalum input capacitors are used, TI recommends that they be surge current tested by the manufacturer.

Use caution when using a high dielectric constant ceramic capacitor for input bypassing, because it may cause severe ringing at the VINpin.

The important parameters for the input capacitor are the input voltage rating and the RMS current rating. With a nominal input voltage of 28 V, an aluminum electrolytic aluminum electrolytic capacitor with a voltage rating greater than 42 V (1.5 × VIN) is required. Because the the next higher capacitor voltage rating is 50 V, a 50-V capacitor must 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 3-A load, a capacitor with a RMS current rating of at least 1.5 A is required.

Figure 23 can be used to select an appropriate input capacitor. From the curves, locate the 50-V line and note

which capacitor values have RMS current ratings greater than 1.5 A. Either a 470 μF or 680 μF, 50-V capacitor could be used.

For a through hole design, a 680-μF, 50-V 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.

Product Folder Links: LM2596

LM2596

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SNVS124E –NOVEMBER 1999–REVISED FEBRUARY 2020

For surface mount designs, solid tantalum capacitors can be used, but exercise caution with regard to the capacitor surge current rating (see Input Capacitor (CIN) in this data sheet). The TPS series available from AVX, and the 593D series from Sprague are both surge current tested.

9.2.2.3 Application Curves

Discontinuous Mode Switching Waveforms VIN= 20 V, V V, I mΩ

= 500 mA L = 10 μH, C

LOAD

= 330 μF, C

OUT

ESR = 45

A: Output Pin Voltage, 10 V/div. B: Inductor Current 0.5 A/div. C: Output Ripple Voltage, 100 mV/div.

Figure 36. Horizontal Time Base: 2 μs/div

OUT

= 5

Load Transient Response for Discontinuous Mode VIN= 20 V, V

= 5V, I

OUT

ESR = 45 mΩ

OUT

= 500 mA to 2 A, L = 10 μH, C

LOAD

OUT

= 330 μF,

A: Output Voltage, 100 mV/div. (AC) B: 500-mA to 2-A Load Pulse

Figure 37. Horizontal Time Base: 200 μs/div

Product Folder Links: LM2596

LM2596

SNVS124E –NOVEMBER 1999–REVISED FEBRUARY 2020

www.ti.com

10 Power Supply Recommendations

The LM2596 is designed to operate from an input voltage supply up to 40 V. This input supply must be well regulated and able to withstand maximum input current and maintain a stable voltage.

11 Layout

11.1 Layout Guidelines

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 must be wide printed-circuit traces and must be kept as short as possible. For best results, external components must be placed as close to the switcher lC as possible using ground plane construction or single point grounding.

If open core inductors are used, take special care selecting the location and positioning of this type of inductor. Allowing the inductor flux to intersect sensitive feedback, lC groundpath and C

When using the adjustable version, take special care selecting the location of the feedback resistors and the associated wiring. Physically place both resistors near the IC, and route the wiring away from the inductor, especially an open-core type of inductor (see Open-Core Inductors for more information).

11.2 Layout Examples

wiring can cause problems.

OUT

CIN— 470-μF, 50-V, Aluminum Electrolytic Panasonic, HFQ Series C

— 330-μF, 35-V, Aluminum Electrolytic Panasonic, HFQ Series

OUT

D1 — 5-A, 40-V Schottky Rectifier, 1N5825 L1 — 47-μH, L39, Renco, Through Hole Thermalloy Heat Sink #7020

Figure 38. Typical Through-Hole PCB Layout, Fixed Output (1x Size), Double-Sided

Product Folder Links: LM2596

www.ti.com

Layout Examples (continued)

CIN— 470-μF, 50-V, Aluminum Electrolytic Panasonic, HFQ Series C

—220-μF, 35-V Aluminum Electrolytic Panasonic, HFQ Series

OUT

D1—5-A, 40-V Schottky Rectifier, 1N5825 L1—47-μH, L39, Renco, Through Hole R1—1 kΩ, 1% R2—Use formula in Design Procedure CFF—See Table 6. Thermalloy Heat Sink #7020

Figure 39. Typical Through-Hole PCB Layout, Adjustable Output (1x Size), Double-Sided

LM2596

SNVS124E –NOVEMBER 1999–REVISED FEBRUARY 2020

Product Folder Links: LM2596

LM2596

SNVS124E –NOVEMBER 1999–REVISED FEBRUARY 2020

www.ti.com

11.3 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 requires a heat sink under most conditions. The size of the heat sink depends on the input

voltage, the output voltage, the load current and the ambient temperature. Figure 40 shows the LM2596T junction temperature rises above ambient temperature for a 3-A 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 (PCB). 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 PCB copper area that the package is soldered to must be at least 0.4 in2, and ideally must have two 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 required, TI recommends double-sided, multilayer PCB with large copper areas and airflow.

Figure 41 shows the LM2596S (TO-263 package) junction temperature rise above ambient temperature with a 2-

A 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 PCB 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 2 A are used, double-sided or multilayer PCB with large copper areas or airflow might be required, especially for high ambient temperatures and high output voltages.

For the best thermal performance, wide copper traces and generous amounts of PCB copper must 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 PCB 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 PCB 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 can either act as a heat sink taking heat away from the board, or it could add heat to the board.

Product Folder Links: LM2596

www.ti.com

SNVS124E –NOVEMBER 1999–REVISED FEBRUARY 2020

Thermal Considerations (continued)

CIRCUIT DATA FOR TEMPERATURE RISE CURVE TO-220 PACKAGE (T)

Capacitors Through-hole electrolytic Inductor Through-hole, Renco Diode Through-hole, 5-A 40-V, Schottky PCB 3-square inch, single-sided, 2-oz. copper (0.0028″)

LM2596

Figure 40. 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, 5-A 40-V, Schottky PCB 9-square inch, single-sided, 2-oz. copper (0.0028″)

Figure 41. Junction Temperature Rise, TO-263

Product Folder Links: LM2596

LM2596

SNVS124E –NOVEMBER 1999–REVISED FEBRUARY 2020

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12 Device and Documentation Support

12.1 Device Support

12.1.1 Custom Design with WEBENCH Tools

Click here to create a custom design using the LM2596 device with the WEBENCH®Power Designer.

1. Start by entering your VIN, V

2. Optimize your design for key parameters like efficiency, footprint and cost using the optimizer dial and compare this design with other possible solutions from Texas Instruments.

3. WEBENCH Power Designer provides you with a customized schematic along with a list of materials with real time pricing and component availability.

5. Get more information about WEBENCH tools at www.ti.com/webench.

12.2 Receiving Notification of Documentation Updates

To receive notification of documentation updates, navigate to the device product folder on ti.com. In the upper right corner, click on Alert me to register and receive a weekly digest of any product information that has changed. For change details, review the revision history included in any revised document.

OUT

and I

requirements.

OUT

12.3 Support Resources

TI E2E™ support forums are an engineer's go-to source for fast, verified answers and design help — straight

from the experts. Search existing answers or ask your own question to get the quick design help you need. Linked content is provided "AS IS" by the respective contributors. They do not constitute TI specifications and do

not necessarily reflect TI's views; see TI's Terms of Use.

12.4 Trademarks

E2E is a trademark of Texas Instruments. SIMPLE SWITCHER, WEBENCH are registered trademarks of Texas Instruments. All other trademarks are the property of their respective owners.

12.5 Electrostatic Discharge Caution

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.

12.6 Glossary

SLYZ022 — TI Glossary.

This glossary lists and explains terms, acronyms, and definitions.

13 Mechanical, Packaging, and Orderable Information

The following pages include mechanical, packaging, and orderable information. This information is the most current data available for the designated devices. This data is subject to change without notice and revision of this document. For browser-based versions of this data sheet, refer to the left-hand navigation.

Product Folder Links: LM2596

PACKAGE OPTION ADDENDUM

www.ti.com

PACKAGING INFORMATION

Orderable Device Status

LM2596S-12/NOPB ACTIVE DDPAK/

LM2596S-3.3 NRND DDPAK/

LM2596S-3.3/NOPB ACTIVE DDPAK/

LM2596S-5.0 NRND DDPAK/

LM2596S-5.0/NOPB ACTIVE DDPAK/

LM2596S-ADJ/NOPB ACTIVE DDPAK/

LM2596SX-12/NOPB ACTIVE DDPAK/

LM2596SX-3.3/NOPB ACTIVE DDPAK/

LM2596SX-5.0/NOPB ACTIVE DDPAK/

LM2596SX-ADJ NRND DDPAK/

LM2596SX-ADJ/NOPB ACTIVE DDPAK/

LM2596T-12/LF03 ACTIVE TO-220 NDH 5 45 RoHS & Green SN Level-1-NA-UNLIM LM2596T

LM2596T-12/NOPB ACTIVE TO-220 NDH 5 45 RoHS & Green SN Level-1-NA-UNLIM LM2596T

LM2596T-3.3/LF03 ACTIVE TO-220 NDH 5 45 RoHS & Green SN Level-1-NA-UNLIM LM2596T

LM2596T-3.3/NOPB ACTIVE TO-220 NDH 5 45 RoHS & Green SN Level-1-NA-UNLIM LM2596T

LM2596T-5.0 NRND TO-220 NDH 5 45 Non-RoHS &

LM2596T-5.0/LF03 ACTIVE TO-220 NDH 5 45 RoHS & Green SN Level-1-NA-UNLIM LM2596T

Package Type Package

(1)

TO-263

Drawing

Pins Package

Qty

Eco Plan

(2)

KTT 5 45 RoHS-Exempt

& Green

KTT 5 45 Non-RoHS &

Non-Green

KTT 5 45 RoHS-Exempt

& Green

KTT 5 45 Non-RoHS &

Non-Green

KTT 5 45 RoHS-Exempt

& Green

KTT 5 45 RoHS-Exempt

& Green

KTT 5 500 RoHS-Exempt

& Green

KTT 5 500 RoHS-Exempt

& Green

KTT 5 500 RoHS-Exempt

& Green

KTT 5 500 Non-RoHS &

Non-Green

KTT 5 500 RoHS-Exempt

& Green

Non-Green

Lead finish/ Ball material

(6)

MSL Peak Temp

(3)

Op Temp (°C) Device Marking

SN Level-3-245C-168 HR LM2596S

Call TI Call TI LM2596S

SN Level-3-245C-168 HR LM2596S

Call TI Call TI LM2596S

SN Level-3-245C-168 HR LM2596S

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

SN Level-3-245C-168 HR LM2596S

Call TI Call TI -40 to 125 LM2596S

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

Call TI Call TI LM2596T

10-Dec-2020

Samples

(4/5)

-12 P+

-3.3 P+

-5.0 P+

-ADJ P+

-12 P+

-3.3 P+

-5.0 P+

-ADJ P+

-12 P+

-3.3 P+

-5.0 P+

Addendum-Page 1

PACKAGE OPTION ADDENDUM

www.ti.com

Orderable Device Status

LM2596T-5.0/NOPB ACTIVE TO-220 NDH 5 45 RoHS & Green SN Level-1-NA-UNLIM LM2596T

LM2596T-ADJ NRND TO-220 NDH 5 45 Non-RoHS &

LM2596T-ADJ/LF02 ACTIVE TO-220 NEB 5 45 RoHS & Green SN Level-1-NA-UNLIM LM2596T

LM2596T-ADJ/NOPB ACTIVE TO-220 NDH 5 45 RoHS & Green SN Level-1-NA-UNLIM -40 to 125 LM2596T

(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.

Package Type Package

(1)

Drawing

Pins Package

Qty

Eco Plan

(2)

Non-Green

Lead finish/ Ball material

(6)

Call TI Call TI -40 to 125 LM2596T

MSL Peak Temp

(3)

Op Temp (°C) Device Marking

-5.0 P+

-ADJ P+

10-Dec-2020

(4/5)

(2)

RoHS: TI defines "RoHS" to mean semiconductor products that are compliant with the current EU RoHS requirements for all 10 RoHS substances, including the requirement that RoHS substance

do not exceed 0.1% by weight in homogeneous materials. Where designed to be soldered at high temperatures, "RoHS" products are suitable for use in specified lead-free processes. TI may reference these types of products as "Pb-Free".

RoHS Exempt: TI defines "RoHS Exempt" to mean products that contain lead but are compliant with EU RoHS pursuant to a specific EU RoHS exemption. Green: TI defines "Green" to mean the content of Chlorine (Cl) and Bromine (Br) based flame retardants meet JS709B low halogen requirements of <=1000ppm threshold. Antimony trioxide based

flame retardants must also meet the <=1000ppm threshold requirement.

(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.

(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 finish/Ball material - Orderable Devices may have multiple material finish options. Finish options are separated by a vertical ruled line. Lead finish/Ball material 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

Samples

Addendum-Page 2

PACKAGE OPTION ADDENDUM

www.ti.com

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.

10-Dec-2020

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 13-Feb-2020

TAPE AND REEL INFORMATION

*All dimensions are nominal

Device Package

Type

LM2596SX-12/NOPB DDPAK/

TO-263

LM2596SX-3.3/NOPB DDPAK/

TO-263

LM2596SX-5.0/NOPB DDPAK/

TO-263

LM2596SX-ADJ DDPAK/

TO-263

LM2596SX-ADJ/NOPB DDPAK/

TO-263

Package Drawing

Pins SPQ Reel

Diameter

(mm)

KTT 5 500 330.0 24.4 10.75 14.85 5.0 16.0 24.0 Q2

Reel

Width

W1 (mm)

(mm)B0(mm)K0(mm)P1(mm)W(mm)

Pin1

Quadrant

Pack Materials-Page 1

PACKAGE MATERIALS INFORMATION

www.ti.com 13-Feb-2020

*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/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

Pack Materials-Page 2

NEB0005B

MECHANICAL DATA

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NEB0005E

MECHANICAL DATA

www.ti.com

NDH0005D

MECHANICAL DATA

www.ti.com

KTT0005B

MECHANICAL DATA

BOTTOM SIDE OF PACKAGE

TS5B (Rev D)

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FREI DEBO DCDC DOWN 2 Datasheet

Specifications and Main Features

Frequently Asked Questions

User Manual

1 Features

2 Applications

3 Description

Table of Contents

4 Revision History

5 Description (continued)

6 Pin Configuration and Functions

7 Specifications

7.1 Absolute Maximum Ratings

7.2 ESD Ratings

7.3 Operating Conditions

7.4 Thermal Information

7.5 Electrical Characteristics – 3.3-V Version

7.6 Electrical Characteristics – 5-V Version

7.7 Electrical Characteristics – 12-V Version

7.8 Electrical Characteristics – Adjustable Voltage Version

7.9 Electrical Characteristics – All Output Voltage Versions

7.10 Typical Characteristics

8 Detailed Description

8.1 Overview

8.2 Functional Block Diagram

8.3 Feature Description

8.3.1 Delayed Start-Up

8.3.2 Undervoltage Lockout

8.3.3 Inverting Regulator

8.3.4 Inverting Regulator Shutdown Methods

8.4 Device Functional Modes

8.4.1 Discontinuous Mode Operation

9 Application and Implementation

9.1 Application Information

9.1.1 Input Capacitor (CIN)

9.1.2 Feedforward Capacitor (CFF)

9.1.4 Catch Diode

9.1.5 Inductor Selection

9.1.6 Output Voltage Ripple and Transients

9.1.7 Open-Core Inductors

9.2 Typical Applications

9.2.1 LM2596 Fixed Output Series Buck Regulator

9.2.1.1 Design Requirements

9.2.1.2 Detailed Design Procedure

9.2.1.3 Application Curves

9.2.2 LM2596 Adjustable Output Series Buck Regulator

9.2.2.1 Design Requirements

9.2.2.2 Detailed Design Procedure

9.2.2.3 Application Curves

10 Power Supply Recommendations

11 Layout

11.1 Layout Guidelines

11.2 Layout Examples

11.3 Thermal Considerations

12 Device and Documentation Support

12.1 Device Support

12.1.1 Custom Design with WEBENCH Tools

12.2 Receiving Notification of Documentation Updates

12.3 Support Resources

12.4 Trademarks

12.5 Electrostatic Discharge Caution

12.6 Glossary

13 Mechanical, Packaging, and Orderable Information