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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.

LM2594

LM2594HV

SNVS118E –DECEMBER 1999–REVISED MAY 2020

LM2594, LM2594HV SIMPLE SWITCHER

Power Converter 150-kHz 0.5-A Step-Down

Voltage Regulator

1 Features

1• New product available: LMR36506 3-V to 65-V

0.6-A ultra-small synchronous buck converter

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

• Adjustable version output voltage range: 1.2 V to

37 V (57-V for the HV version), ±4% maximum

over line and load conditions

• Available in 8-pin surface-mount SOIC and 8-pin

PDIP packages

• Ensured 0.5-A output current

• Input voltage range up to 60 V

• Requires only four external components

• 150-kHz Fixed-frequency internal oscillator

• TTL shutdown capability

• Low power standby mode, IQtypically 85 μA

• High efficiency

• Uses readily-available standard inductors

• Thermal shutdown and current-limit protection

•Start WEBENCH design with LM2594HV

2 Applications

• Simple high-efficiency step-down (buck) regulator

• Efficient preregulator for linear regulators

• On-card switching regulators

• Positive-to-negative convertor

3 Description

The LM2594xx series of regulators are monolithic

integrated circuits that provide all the active functions

for a step-down (buck) switching regulator, capable of

driving a 0.5-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, and are packaged in a 8-pin PDIP and a 8-

pin surface-mount SOIC package.

Requiring a minimum number of external

components, these regulators are simple to use and

feature internal frequency compensation, a fixed-

frequency oscillator, and improved line and load

regulation specifications.

The new product, LMR36506, offers reduced BOM

cost, higher efficiency, and smaller solution size with

many other features. See the Device Comparison

Table to compare specs. Start WEBENCH Design

with LMR36506.

Device Information(1)

PART NUMBER PACKAGE BODY SIZE (NOM)

LM2597, LM2597HV SOIC (8) 4.90 mm × 3.91 mm

PDIP (8) 9.81 mm × 6.35 mm

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

the end of the data sheet.

Typical Application

Fixed Output Voltage Versions

LM2594

LM2594HV

SNVS118E –DECEMBER 1999–REVISED MAY 2020

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Table of Contents

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

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

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

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

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

6 Pin Configuration and Functions......................... 3

7 Specifications......................................................... 4

7.1 Absolute Maximum Ratings ...................................... 4

7.2 ESD Ratings.............................................................. 4

7.3 Recommended Operating Conditions....................... 4

7.4 Thermal Information.................................................. 4

7.5 Electrical Characteristics – 3.3 V.............................. 5

7.6 Electrical Characteristics – 5 V................................. 5

7.7 Electrical Characteristics – 12 V............................... 5

7.8 Electrical Characteristics – Adjustable...................... 6

7.9 Electrical Characteristics – All Output Voltage

Versions..................................................................... 6

7.10 Typical Characteristics............................................ 7

8 Detailed Description............................................ 10

8.1 Overview................................................................. 10

8.2 Functional Block Diagram....................................... 10

8.3 Feature Description................................................. 10

8.4 Device Functional Modes........................................ 14

9 Application and Implementation ........................ 15

9.1 Application Information............................................ 15

9.2 Typical Applications ................................................ 22

10 Power Supply Recommendations ..................... 29

11 Layout................................................................... 30

11.1 Layout Guidelines ................................................. 30

11.2 Layout Example .................................................... 30

11.3 Thermal Considerations........................................ 31

12 Device and Documentation Support................. 33

12.1 Related Links ........................................................ 33

12.2 Support Resources ............................................... 33

12.3 Trademarks........................................................... 33

12.4 Electrostatic Discharge Caution............................ 33

12.5 Glossary................................................................ 33

13 Mechanical, Packaging, and Orderable

Information........................................................... 33

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 information on LMR36506 to Features and Description ............................................................................................. 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 .................................................................................. 31

Not to scale

1NC 8 Output

2NC 7 +VIN

3NC 6 Ground

4Feedback 5 ON/OFF

LM2594

LM2594HV

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SNVS118E –DECEMBER 1999–REVISED MAY 2020

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(1) I = INPUT, O = OUTPUT

5 Description (continued)

A standard series of inductors (both through-hole and surface-mount types) are available from several different

manufacturers optimized for use with the LM2594xx series. This feature greatly simplifies the design of switch-

mode power supplies.

Other features include an ensured ±4% tolerance on output voltage under all conditions of input voltage and

output load conditions, and ±15% on the oscillator frequency. External shutdown is included, featuring typically

85-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.

The LM2594HV is for applications requiring an input voltage up to 60 V.

6 Pin Configuration and Functions

D or P Package

8-Pin SOIC or PDIP

Top View

*No internal connection, but must be soldered to PCB for best heat transfer.

‡Patent Number 5,382,918.

Pin Functions(1)

PIN I/O DESCRIPTION

NO. NAME

1, 2, 3 NC — No connection

4 Feedback I Senses the regulated output voltage to complete the feedback loop.

5 ON/OFF I

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 1.3 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 needed, the

ON/OFF pin can be wired to the ground pin or it can be left open, in either case, the

regulator is in the ON condition.

6 Ground — Circuit ground

7 +VIN IThis is the positive input supply for the IC switching regulator. A suitable input bypass

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

switching currents needed by the regulator.

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

−0.5 V, with a duty cycle of VOUT/VIN. To minimize coupling to sensitive circuitry, the PCB

copper area connected to this pin must be kept to a minimum.

LM2594

LM2594HV

SNVS118E –DECEMBER 1999–REVISED MAY 2020

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(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 TI Sales Office/ Distributors for availability and specifications.

7 Specifications

7.1 Absolute Maximum Ratings(1)(2)

MIN MAX UNIT

Supply voltage LM2594 45 V

LM2594HV 60

ON/OFF pin input voltage −0.3 25 V

Feedback pin voltage −0.3 25 V

Output voltage to ground (steady state) −1 V

Power dissipation Internally limited

Lead temperature D8 package Vapor phase (60 s) 215 °CInfrared (15 s) 220

P package (soldering, 10 s) 260

Maximum junction temperature 150 °C

Storage temperature, Tstg −65 150 °C

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

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

7.2 ESD Ratings VALUE UNIT

V(ESD) Electrostatic discharge Human-body model (HBM), per ANSI/ESDA/JEDEC JS-001(1)(2) ±2000 V

7.3 Recommended Operating Conditions MIN MAX UNIT

Supply voltage LM2594 4.5 40 V

LM2594HV 4.5 60 V

Temperature −40 125 °C

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

report, SPRA953.

(2) The package thermal impedance is calculated in accordance to JESD 51-7.

(3) Thermal resistances were simulated on a 4 -layer, JEDEC board.

7.4 Thermal Information

THERMAL METRIC(1) LM2594, LM2594HV

UNITD (SOIC) P (PDIP)

8 PINS 8 PINS

RθJA Junction-to-ambient thermal resistance(2)(3) 150 95 °C/W

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LM2594HV

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

(2) All limits ensured at room temperature and at temperature extremes. 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).

(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 LM2594xx is used as shown in the Figure 35 test circuit, system performance is as

shown in the system parameters.

7.5 Electrical Characteristics – 3.3 V

Specifications are for TJ= 25°C, VINmax= 40 V for the LM2594 and 60 V for the LM2594HV (unless otherwise noted).

PARAMETER TEST CONDITIONS MIN TYP(1) MAX(2) UNIT

SYSTEM PARAMETERS(3) (see Figure 35 for test circuit)

VOUT Output voltage 4.75 V ≤VIN ≤VINmax,

0.1 A ≤ILOAD ≤0.5 A

TJ= 25°C 3.432 3.3 3.168 V

Over full operating temperature

range 3.465 3.135

ηEfficiency VIN = 12 V, ILOAD = 0.5 A 80%

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

(2) All limits ensured at room temperature and at temperature extremes. 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).

(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 LM2594xx is used as shown in the Figure 35 test circuit, system performance is as

shown in the system parameters.

7.6 Electrical Characteristics – 5 V

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

PARAMETER TEST CONDITIONS MIN TYP(1) MAX(2) UNIT

SYSTEM PARAMETERS(3) (see Figure 35 for test circuit)

VOUT Output voltage 7 V ≤VIN ≤VINmax,

0.1 A ≤ILOAD ≤0.5 A TJ= 25°C 4.8 5 5.2 V

Over full operating temperature range 4.75 5.25

ηEfficiency VIN = 12 V, ILOAD = 0.5 A 82%

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

(2) All limits ensured at room temperature and at temperature extremes. 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).

(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 LM2594/LM2594HV is used as shown in the Figure 35 test circuit, system

performance is as shown in the system parameters.

7.7 Electrical Characteristics – 12 V

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

PARAMETER TEST CONDITIONS MIN TYP(1) MAX(2) UNIT

SYSTEM PARAMETERS(3) (see Figure 35 for test circuit)

VOUT Output voltage 15 V ≤VIN ≤VINmax,

0.1 A ≤ILOAD ≤0.5 A TJ= 25°C 11.52 12 12.48 V

Over full operating temperature range 11.4 12.6

ηEfficiency VIN = 25 V, ILOAD = 0.5 A 88%

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LM2594HV

SNVS118E –DECEMBER 1999–REVISED MAY 2020

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

(2) All limits ensured at room temperature and at temperature extremes. 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).

(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 LM2594/LM2594HV is used as shown in the Figure 35 test circuit, system

performance is as shown in the system parameters.

7.8 Electrical Characteristics – Adjustable

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

PARAMETER TEST CONDITIONS MIN TYP(1) MAX(2) UNIT

SYSTEM PARAMETERS(3) (see Figure 35 for test circuit)

VFB Feedback voltage

4.5 V ≤VIN ≤VINmax,

0.1 A ≤ILOAD ≤0.5 A,

VOUT programmed for 3 V,

Circuit of Figure 35

TJ= 25°C 1.193 1.23 1.267

Over full operating temperature range 1.18 1.28

ηEfficiency VIN = 12 V, ILOAD = 0.5 A 80%

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

(2) All limits ensured at room temperature and at temperature extremes. 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).

(3) The switching frequency is reduced when the second stage current limit is activated. The amount of reduction is determined by the

severity of current overload.

(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 version, and 15 V for the 12-V version,

to force the output transistor switch OFF.

(7) VIN = 40 V for the LM2594 and 60 V for the LM2594HV.

7.9 Electrical Characteristics – All Output Voltage Versions

Specifications are for TJ= 25°C, VIN = 12 V for the 3.3-V, 5-V, and adjustable version, and VIN = 24 V for the 12-V version,

ILOAD = 100 mA (unless otherwise noted).

PARAMETER TEST CONDITIONS MIN TYP(1) MAX(2) UNIT

DEVICE PARAMETERS

IbFeedback bias current Adjustable version only, VFB =

1.3 V TJ= 25°C 10 50 nA

Over full operating temperature range 100

fOOscillator frequency See(3) TJ= 25°C 127 150 173 kHz

Over full operating temperature range 110 173

VSAT Saturation voltage IOUT = 0.5 A(4)(5) TJ= 25°C 0.9 1.1 V

Over full operating temperature range 1.2

DC Max duty cycle (ON) See(5) 100%

Min duty cycle (OFF) See(6) 0%

ICL Current limit Peak current(4)(5) TJ= 25°C 0.65 0.8 1.3 A

over full operating temperature range 0.58 1.4

ILOutput leakage current Output = 0 V(4)(6)(7)

Output = −1 V 50 μA

2 15 mA

IQQuiescent current See(6) 5 10 mA

ISTBY Standby quiescent

current

ON/OFF pin = 5 V (OFF)(7) 85 μA

LM2594 TJ= 25°C 200 μA

Over full operating temperature range 250

LM2594HV TJ= 25°C 140 250 μA

Over full operating temperature range 300

ON/OFF CONTROL (see Figure 35 for test circuit)

ON/OFF pin logic input 1.3 V

VIH Threshold voltage Low (regulator ON), over full operating temperature range 0.6 V

VIL High (regulator OFF), over full operating temperature range 2 V

IHON/OFF pin input

current VLOGIC = 2.5 V (regulator OFF) 5 15 μA

ILVLOGIC = 0.5 V (regulator ON) 0.02 5 μA

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7.10 Typical Characteristics

Figure 1. Normalized Output Voltage Figure 2. Line Regulation

Figure 3. Efficiency Figure 4. Switch Saturation Voltage

Figure 5. Switch Current Limit Figure 6. Dropout Voltage

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LM2594HV

SNVS118E –DECEMBER 1999–REVISED MAY 2020

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Typical Characteristics (continued)

Figure 7. Quiescent Current Figure 8. Standby Quiescent Current

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)

Figure 13. Feedback Pin Bias Current

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8 Detailed Description

8.1 Overview

The LM2594 SIMPLE SWITCHER®regulator is an easy-to-use, nonsynchronous step-down DC-DC converter

with a wide input voltage range from 45 V to up to 60 V for a HV version. The regulator is capable of delivering

up to 0.5-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, the 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 1 V). If hysteresis is needed, 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-kΩresistor is needed

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 regulators ground pin to the negative output voltage, then grounding the

feedback pin, the regulator senses the inverted output voltage and regulates it.

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

Figure 16. Undervoltage Lockout for Inverting Regulator

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LM2594HV

SNVS118E –DECEMBER 1999–REVISED MAY 2020

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Feature Description (continued)

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

120-μF, 35-V Elec. Panasonic HFQ

COUT — 22-μF, 20-V Tant. Sprague 595D

39-μF, 16-V Elec. Panasonic HFQ

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

This example uses the LM2594-5 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 LM2594 has a maximum input voltage specification of 40 V (60

V for the LM2594HV).

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 closely resemble a buck configuration thus providing good closed loop stability.

TI recommends 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 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.

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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 100-μH, 1-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 provides 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 LM2594 current limit (approximately 0.8 A) 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 start-up currents

required by the inverting topology, the delayed start-up feature (C1, R1and 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 needed 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

To use the ON/OFF pin in a standard buck configuration is simple; pull it below 1.3 V (at 25°C, referenced to

ground) to turn regulator ON and pull it above 1.3 V 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 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 and high input voltages, a discontinuous mode design can be a better choice. Discontinuous mode

would use an inductor that is physically smaller, and would need only one half to one third of the inductance

value needed for a continuous mode design. The peak switch and inductor currents are higher in a discontinuous

design, but at these low load currents (200 mA and below), the maximum switch current is still 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 33). 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 or 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 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 can 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. The

capacitor 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 the input capacitor of the buck regulator, 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 determines the amount of current the capacitor can safely sustain.

Capacitors that are physically large and have a large surface area typically has a higher RMS current ratings. 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 has 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 electrolyte of the capacitor, 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.

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

9.1.2 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 ESR of the selected capacitor 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, provides 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 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 24). 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 Figure 30 and Table 7 for typical capacitor values,

voltage ratings, and manufacturers capacitor types.

Electrolytic capacitors are not recommended for temperatures below −25°C. The ESR rises dramatically at cold

temperatures and typically rises three times at −25°C and as much as ten times 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.

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

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Application Information (continued)

Table 1. Output Capacitor and Feedforward Capacitor Selection Table

OUTPUT

VOLTAGE

(V)

THROUGH-HOLE OUTPUT CAPACITOR SURFACE-MOUNT OUTPUT CAPACITOR

PANASONIC HFQ

SERIES (µF/V) NICHICON PL

SERIES (µF/V) FEEDFORWARD

CAPACITOR AVX TPS SERIES

(µF/V) SPRAGUE 595D

SERIES (µF/V) FEEDFORWARD

CAPACITOR

1.2 220/25 220/25 0 220/10 220/10 0

4 180/25 180/25 4.7 nF 100/10 120/10 4.7 nF

6 82/25 82/25 4.7 nF 100/10 120/10 4.7 nF

9 82/25 82/25 3.3 nF 100/16 100/16 3.3 nF

12 82/25 82/25 2.2 nF 100/16 100/16 2.2 nF

15 82/25 82/25 1.5 nF 68/20 100/20 1.5 nF

24 82/50 120/50 1 nF 10/35 15/35 220 pF

28 82/50 120/50 820 pF 10/35 15/35 220 pF

9.1.3 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 LM2594 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 1N4001 series are much too slow and must not be used.

Figure 25. Capacitor ESR Change versus Temperature

Table 2. Diode Selection Table

1-A DIODES

SURFACE MOUNT THROUGH HOLE

SCHOTTKY ULTRA FAST RECOVERY SCHOTTKY ULTRA FAST RECOVERY

20 V

All of these diodes are rated to

at least 60 V.

1N5817

All of these diodes are rated to

at least 60 V.

SR102

MBRS130 1N5818

30 V SR103

11DQ03

MBRS140 MURS120 1N5819 MUR120

40 V 10BQ040 10BF10 SR104 HER101

10MQ040 11DQ04 11DF1

50 V

MBRS160 SR105

10BQ050 MBR150

10MQ060 11DQ05

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Table 2. Diode Selection Table (continued)

1-A DIODES

SURFACE MOUNT THROUGH HOLE

SCHOTTKY ULTRA FAST RECOVERY SCHOTTKY ULTRA FAST RECOVERY

MBRS1100 MBR160

10MQ090 SB160

SGL41-60 11DQ10

SS16

9.1.4 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 operates in the

discontinuous mode when the load current is low.

The LM2594 (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. This mode offers greater output power,

lower peak switch, inductor, and diode currents, and can have lower output ripple voltage. However, the

continuous mode requires larger inductor values to keep the inductor current flowing continuously, especially at

low output load currents and high input voltages.

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 allows 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. (ΔIIND) Peak-to-Peak Inductor 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 wrapped on a ferrite bobbin. This type of construction makes for a inexpensive inductor;

however, 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).

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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 the maximum current rating of the inductor can cause the inductor to overheat because of the copper

wire losses, or the core can 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 the LM2594. Different inductor types have different

saturation characteristics, and this must be kept in mind when selecting an inductor.

The inductor manufacturers 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.

Figure 27. LM2594xx 3.3-V Figure 28. LM2594xx 5-V

Figure 29. LM2594xx 12-V Figure 30. LM2594xx Adjustable Voltage

Table 3. Inductor Manufacturers Part Numbers

INDUCTANCE

(μH) CURRENT

(A)

SCHOTTKY RENCO PULSE ENGINEERING COILCRAFT

THROUGH

HOLE SURFACE

MOUNT THROUGH

HOLE SURFACE

MOUNT THROUGH

HOLE SURFACE

MOUNT SURFACE

MOUNT

L1 220 0.18 67143910 67144280 RL-5470-3 RL1500-220 PE-53801 PE-53801-S DO1608-224

L2 150 0.21 67143920 67144290 RL-5470-4 RL1500-150 PE-53802 PE-53802-S DO1608-154

L3 100 0.26 67143930 67144300 RL-5470-5 RL1500-100 PE-53803 PE-53803-S DO1608-104

L4 68 0.32 67143940 67144310 RL-1284-68 RL1500-68 PE-53804 PE-53804-S DO1608-68

L5 47 0.37 67148310 67148420 RL-1284-47 RL1500-47 PE-53805 PE-53805-S DO1608-473

L6 33 0.44 67148320 67148430 RL-1284-33 RL1500-33 PE-53806 PE-53806-S DO1608-333

L7 22 0.60 67148330 67148440 RL-1284-22 RL1500-22 PE-53807 PE-53807-S DO1608-223

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Table 3. Inductor Manufacturers Part Numbers (continued)

INDUCTANCE

(μH) CURRENT

(A)

SCHOTTKY RENCO PULSE ENGINEERING COILCRAFT

THROUGH

HOLE SURFACE

MOUNT THROUGH

HOLE SURFACE

MOUNT THROUGH

HOLE SURFACE

MOUNT SURFACE

MOUNT

L8 330 0.26 67143950 67144320 RL-5470-2 RL1500-330 PE-53808 PE-53808-S DO3308-334

L9 220 0.32 67143960 67144330 RL-5470-3 RL1500-220 PE-53809 PE-53809-S DO3308-224

L10 150 0.39 67143970 67144340 RL-5470-4 RL1500-150 PE-53810 PE-53810-S DO3308-154

L11 100 0.48 67143980 67144350 RL-5470-5 RL1500-100 PE-53811 PE-53811-S DO3308-104

L12 68 0.58 67143990 67144360 RL-5470-6 RL1500-68 PE-53812 PE-53812-S DO1608-683

L13 47 0.70 67144000 67144380 RL-5470-7 RL1500-47 PE-53813 PE-53813-S DO3308-473

L14 33 0.83 67148340 67148450 RL-1284-33 RL1500-33 PE-53814 PE-53814-S DO1608-333

L15 22 0.99 67148350 67148460 RL-1284-22 RL1500-22 PE-53815 PE-53815-S DO1608-223

L16 15 1.24 67148360 67148470 RL-1284-15 RL1500-15 PE-53816 PE-53816-S DO1608-153

L17 330 0.42 67144030 67144410 RL-5471-1 RL1500-330 PE-53817 PE-53817-S DO3316-334

L18 220 0.55 67144040 67144420 RL-5471-2 RL1500-220 PE-53818 PE-53818-S DO3316-224

L19 150 0.66 67144050 67144430 RL-5471-3 RL1500-150 PE-53819 PE-53819-S DO3316-154

L20 100 0.82 67144060 67144440 RL-5471-4 RL1500-100 PE-53820 PE-53820-S DO3316-104

L21 68 0.99 67144070 67144450 RL-5471-5 RL1500-68 PE-53821 PE-53821-S DDO3316-683

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

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

9.1.5 Output Voltage Ripple and Transients

The output voltage of a switching power supply operating in the continuous mode contains a sawtooth ripple

voltage at the switcher frequency, and can 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 15 mV), TI recommends a post ripple filter (see Figure 35).

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 can 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 three-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 must 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 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.

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Figure 31. Peak-to-Peak Inductor

Ripple Current vs Load Current

In a switching regulator design, knowing the value of the peak-to-peak inductor ripple current (ΔIIND) can be

useful for determining a number of other circuit parameters. Parameters such as, peak inductor or peak switch

current, minimum load current before the circuit becomes discontinuous, output ripple voltage and output

capacitor ESR can all be calculated from the peak-to-peak ΔIIND. When the inductor nomographs shown in

Figure 27 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 (ΔIIND) that can be expected for different load currents.

Figure 31 also shows how the peak-to-peak inductor ripple current (ΔIIND) changes as the designer goes 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).

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 = 5 V, maximum load current of 300 mA

VIN = 15 V, nominal, varying between 11 V and 20 V

The selection guide in Figure 28 shows that the vertical line for a 0.3-A load current and the horizontal line for the

15-V input voltage intersect approximately midway between the upper and lower borders of the 150-μH

inductance region. A 150-μH inductor allows a peak-to-peak inductor current (ΔIIND) to flow a percentage of the

maximum load current. Referring to Figure 31, follow the 0.3-A line approximately midway into the inductance

region, and read the peak-to-peak inductor ripple current (ΔIIND) on the left hand axis (approximately 150 mAp-p).

As the input voltage increases to 20 V, it approaches the upper border of the inductance region, and the inductor

ripple current increases. Figure 31 shows that for a load current of 0.3 A, the peak-to-peak inductor ripple current

(ΔIIND) is 150 mA with 15V in, and can range from 175 mA at the upper border (20 V in) to 120 mA at the lower

border (11 V 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)

– = 0.150 A × 0.240 Ω= 36 mVp-p

– or

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4. ESR of COUT

9.1.6 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 induces 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 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 corrects 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 must be minimized.

Sometimes, locating a trace directly beneath a bobbin inductor provides 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.

9.2 Typical Applications

9.2.1 Series Buck Regulator (Fixed Output)

Select components with higher voltage ratings for designs using the LM2594HV with an input voltage between 40

V and 60 V.

CIN — 68-μF, 35-V, Aluminum Electrolytic Nichicon “PL Series”

COUT — 120-μF, 25-V Aluminum Electrolytic, Nichicon “PL Series”

D1 — 1-A, 40-V Schottky Rectifier, 1N5819

L1 — 100-μH, L20

Figure 32. Fixed Output Voltage Versions

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Typical Applications (continued)

9.2.1.1 Design Requirements

Table 4 lists the design parameters of this example.

Table 4. Design Parameters

PARAMETER EXAMPLE VALUE

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

Maximum DC input voltage, VIN(max) 12 V

Maximum load current, ILOAD(max) 0.4 A

9.2.1.2 Detailed Design Procedure

9.2.1.2.1 Inductor Selection (L1)

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

3.3 V, 5 V, or 12 V, respectively). For all other voltages, see Detailed Design Procedure for the adjustable

version.

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 0.4-A vertical line is 100 μH, and the inductor code is L20.

3. Select an appropriate inductor from the four manufacturer's part numbers listed in Table 3.

The inductance value required is 100 μH. See row L20 of Table 3 and choose an inductor part number from

any of the four manufacturers shown. (In most instance, both through-hole and surface-mount inductors are

available.)

9.2.1.2.2 Output Capacitor Selection (COUT)

1. In the majority of applications, low ESR (Equivalent Series Resistance) electrolytic capacitors between 82 μF

and 220 μF and low-ESR, solid tantalum capacitors between 15 μF and 100 μF provide the best results. This

capacitor must be located close to the IC using short capacitor leads and short copper traces. Do not use

capacitors larger than 220 μF. For additional information, see Output Capacitor (COUT).

2. To simplify the capacitor selection procedure, see Figure 30 for quick design component selection. This table

contains different input voltages, output voltages, and load currents, and lists various inductors and output

capacitors that provides the best design solutions.

From Figure 30, 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 0.5-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 this line shows the recommended inductors and capacitors that

provides the best overall performance.

The capacitor list contains both through hole electrolytic and surface mount tantalum capacitors from four

different capacitor manufacturers. TI recommends using both the manufacturers and the manufacturer's

series that are listed in Table 5.

In this example, aluminum electrolytic capacitors from several different manufacturers are available with the

range of ESR numbers needed:

120-μF, 2-5V Panasonic HFQ Series

120-μF, 2-5V Nichicon PL Series

3. The capacitor voltage rating for electrolytic capacitors must 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.

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For a 5-V output, a capacitor voltage rating at least 7.5 V or more is required. But, in this example, even a

low ESR, switching grade, 120-μF, 10-V aluminum electrolytic capacitor would exhibit approximately 400 mΩ

of ESR (see Figure 24 for the ESR vs voltage rating). This amount of ESR would result in relatively high

output ripple voltage. To reduce the ripple to 1% of the output voltage, or less, a capacitor with a higher

voltage rating (lower ESR) must be selected. A 16-V or 25-V capacitor reduces the ripple voltage by

approximately half.

9.2.1.2.3 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 LM2594. The most stressful condition for this diode is an overload or

shorted output condition.

See Table 2. In this example, a 1-A, 20-V, 1N5817 Schottky diode provides the best performance, 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 located close to the LM2594 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. Ultra-

fast recovery diodes typically have reverse recovery times of 50 ns or less. Rectifiers such as the 1N4001

must not be used because they are too slow.

9.2.1.2.4 Input Capacitor (CIN)

A low ESR aluminum or tantalum bypass capacitor is needed between the input pin and ground to prevent large

voltage transients from appearing at the input. In addition, the RMS current rating of the input capacitor must 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 located 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 ceramic capacitors for input bypassing, because it may cause severe ringing at the VIN

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 400-mA load, a capacitor with a RMS current rating of at least 200 mA is needed.

Figure 23 can be used to select an appropriate input capacitor. From the curves, locate the 25-V line and note

which capacitor values have RMS current ratings greater than 200 mA. Either a 47-μF or 68-μF, 25-V capacitor

can be used.

For a through hole design, a 68-μF, 25-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 are recommended. The TPS series available from AVX,

and the 593D series from Sprague are both surge current tested.

For additional information, see Input Capacitor (CIN).

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Table 5. LM2594xx Fixed Voltage Quick Design Component Selection Table

CONDITIONS INDUCTOR OUTPUT CAPACITOR

THROUGH HOLE SURFACE MOUNT

OUTPUT

VOLTAGE

(V)

LOAD

CURRENT

(A)

MAX INPUT

VOLTAGE

(V)

INDUCTANCE

(μH) INDUCTOR

(#)

PANASONIC

HFQ SERIES

(μF/V)

NICHICON

PL SERIES

(μF/V)

AVX TPS

SERIES

(μF/V)

SPRAGUE

595D SERIES

(μF/V)

3.3

0.5

5 33 L14 220/16 220/16 100/16 100/6.3

7 47 L13 120/25 120/25 100/16 100/6.3

10 68 L21 120/25 120/25 100/16 100/6.3

40 100 L20 120/35 120/35 100/16 100/6.3

6 68 L4 120/25 120/25 100/16 100/6.3

0.2 10 150 L10 120/16 120/16 100/16 100/6.3

40 220 L9 120/16 120/16 100/16 100/6.3

0.5

8 47 L13 180/16 180/16 100/16 33/25

10 68 L21 180/16 180/16 100/16 33/25

15 100 L20 120/25 120/25 100/16 33/25

40 150 L19 120/25 120/25 100/16 33/25

9 150 L10 82/16 82/16 100/16 33/25

0.2 20 220 L9 120/16 120/16 100/16 33/25

40 330 L8 120/16 120/16 100/16 33/25

0.5

15 68 L21 82/25 82/25 100/16 15/25

18 150 L19 82/25 82/25 100/16 15/25

30 220 L27 82/25 82/25 100/16 15/25

40 330 L26 82/25 82/25 100/16 15/25

15 100 L11 82/25 82/25 100/16 15/25

0.2 20 220 L9 82/25 82/25 100/16 15/25

40 330 L17 82/25 82/25 100/16 15/25

9.2.1.3 Application Curves

Discontinuous mode switching waveforms

VIN = 20 V, VOUT = 5 V, ILOAD = 200 mA

L = 33 μH, COUT = 220 μF, COUT ESR = 60 mΩ

A: Output pin voltage, 10 V/div.

B: Inductor current, 0.2 A/div.

C: Output ripple voltage, 20 mV/div.

Figure 33. Horizontal Time Base: 2 μs/div

Load transient response for discontinuous mode

VIN = 20 V, VOUT = 5 V, ILOAD = 100 mA to 200 mA

L = 33 μH, COUT = 220 μF, COUT ESR = 60 mΩ

A: Output voltage, 50 mV/div. (AC)

B: 100-mA to 200-mA load pulse

Figure 34. Horizontal Time Base: 200 μs/div

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9.2.2 Series Buck Regulator (Adjustable Output)

CIN — 68-μF, 35-V, Aluminum Electrolytic Nichicon “PL Series”

COUT — 120-μF, 25-V Aluminum Electrolytic, Nichicon “PL Series”

D1 — 1-A, 40-V Schottky Rectifier, 1N5819

L1 — 100-μH, L20

R1— 1 kΩ, 1%

CFF — See Feedforward Capacitor (CFF)

Figure 35. Adjustable Output Voltage Version

9.2.2.1 Design Requirements

Table 6 lists the design parameters of this example.

Table 6. Design Parameter

PARAMETER EXAMPLE VALUE

Regulated output voltage, VOUT 20 V

Maximum input voltage, VIN(max) 28 V

Maximum load current, ILOAD(max) 0.5 A

Switching frequency, F Fixed at a nominal 150 kHz

9.2.2.2 Detailed Design Procedure

9.2.2.2.1 Programming Output Voltage

Selecting R1and R2, as shown in Figure 35.

Use Equation 1 to select the appropriate resistor values.

(1)

Select R1to be 1 kΩ, 1%. Solve for R2using Equation 2.

(2)

Select a value for R1between 240 Ωand 1.5 kΩusing Equation 3. 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.)

LM2594

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(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

• VSAT = internal switch saturation voltage = 0.9 V

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

2. Calculate the inductor Volt • microsecond constant (E × T) with Equation 5.

(5)

3. 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 = 35.2 (V × μs) (6)

4. On the horizontal axis, select the maximum load current: ILOAD(max) = 0.5 A

5. 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 35 (V ×

μs) horizontal line and the 0.5-A vertical line is 150 μH, and the inductor code is L19.

6. Select an appropriate inductor from the four manufacturer's part numbers listed in Table 3.

From Table 3, locate line L19, and select an inductor part number from the list of manufacturers' part

numbers.

9.2.2.2.3 Output Capacitor Selection (COUT)

1. In the majority of applications, low ESR electrolytic or solid tantalum capacitors between 82 μF and 220 μF

provide the best results. This capacitor must be located close to the IC using short capacitor leads and short

copper traces. Do not use capacitors larger than 220 μF. For additional information, see Output Capacitor

(COUT).

2. To simplify the capacitor selection procedure, see Table 7 for a quick design guide. This table contains

different output voltages, and lists various output capacitors that provides the best design solutions.

From Table 7, 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 Output Capacitor (COUT),

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 7.

In this example, through hole aluminum electrolytic capacitors from several different manufacturers are

available.

82-µF, 50-V Panasonic HFQ Series

120-µF, 50-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 needed to satisfy the low ESR requirements needed for low output ripple voltage.

For a 20-V output, a capacitor rating of at least 30-V or more is required. In this example, either a 35-V or

50-V capacitor would work. A 50-V rating was chosen because it has a lower ESR which provides a lower

output ripple voltage.

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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 7. Refer to the capacitor manufacturers

data sheet for this information.

9.2.2.2.4 Feedforward Capacitor (CFF)

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

capacitor is typically between 50 pF and 10 nF, and is wired in parallel with the output voltage setting resistor,

R2. It provides additional stability for high output voltages, low input or output voltages, and very low ESR output

capacitors, such as solid tantalum capacitors calculated with Equation 7.

(7)

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 7 contains feedforward capacitor values for various output voltages. In this example, a 1-nF capacitor is

needed.

9.2.2.2.5 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 LM2594. The most stressful condition for this diode is an overload or

shorted output condition.

See Table 2. Schottky diodes provide the best performance, and in this example a 1-A, 40-V, 1N5819

Schottky diode is a good choice. The 1-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 LM2594 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 must 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 located 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 ceramic capacitors for input bypassing, because it may cause severe ringing at the VIN

pin.

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 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 400 mA load, a capacitor with a RMS current rating of at least 200 mA is needed.

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Figure 23 shows curves that 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 200 mA. A 47-μF, 50-V low

ESR electrolytic capacitor is needed.

For a through-hole design, a 47-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.

For surface mount designs, solid tantalum capacitors are recommended. The TPS series available from AVX,

and the 593D series from Sprague are both surge current tested.

For additional information, see Input Capacitor (CIN).

Table 7. Output Capacitor and Feedforward Capacitor Selection Table

OUTPUT

VOLTAGE

(V)

THROUGH-HOLE OUTPUT CAPACITOR SURFACE-MOUNT OUTPUT CAPACITOR

PANASONIC HFQ

SERIES (μF/V) NICHICON PL SERIES

(μF/V) FEEDFORWARD

CAPACITOR AVX TPS

SERIES (μF/V) SPRAGUE 595D

SERIES (μF/V) FEEDFORWARD

CAPACITOR

1.2 220/25 220/25 0 220/10 220/10 0

4 180/25 180/25 4.7 nF 100/10 120/10 4.7 nF

6 82/25 82/25 4.7 nF 100/10 120/10 4.7 nF

9 82/25 82/25 3.3 nF 100/16 100/16 3.3 nF

12 82/25 82/25 2.2 nF 100/16 100/16 2.2 nF

15 82/25 82/25 1.5 nF 68/20 100/20 1.5 nF

24 82/50 120/50 1 nF 10/35 15/35 220 pF

28 82/50 120/50 820 pF 10/35 15/35 220 pF

9.2.2.3 Application Curves

Continuous mode switching waveforms

VIN = 20 V, VOUT = 5 V, ILOAD = 400 mA

L = 100 μH, COUT = 120 μF, COUT ESR = 140 mΩ

A: Output pin voltage, 10 V/div.

B: Inductor current, 0.2 A/div.

C: Output ripple voltage, 20 mV/div.

Figure 36. Horizontal Time Base: 2 μs/div

Load transient response for continuous mode

VIN = 20 V, VOUT = 5 V, ILOAD = 200 mA to 500 mA

L = 100 μH, COUT = 120 μF, COUT ESR = 140 mΩ

A: Output voltage, 50 mV/div. (AC)

B: 200-mA to 500-mA load pulse

Figure 37. Horizontal Time Base: 50 μs/div

10 Power Supply Recommendations

The LM2594 is designed to operate from an input voltage supply up to 45 V and 60 V (HV version). This input

supply must be well regulated and able to withstand maximum input current and maintain a stable voltage.

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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, 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, take special care regarding as to 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.

11.2 Layout Example

CIN = 10-μF, 35-V, Solid Tantalum AVX, TPS series

COUT = 00-μF, 10-V Solid Tantalum AVX, TPS series

D1 = 1-A, 40-V Schottky Rectifier, surface mount

L1 = 100-μH, L20, Coilcraft DO33

Figure 38. Typical Surface-Mount PCB Layout, Fixed Output (2X Size)

CIN = 10-μF, 35-V, Solid Tantalum AVX, TPS series

COUT = 100-μF, 10-V Solid Tantalum AVX, TPS series

D1 = 1-A, 40-V Schottky Rectifier, surface mount

L1 = 100-μH, L20, Coilcraft DO33

R1 = 1 kΩ, 1%

R2= Use formula in Design Procedure

CFF = See Table 7

Figure 39. Typical Surface-Mount PCB Layout, Adjustable Output (2X Size)

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11.3 Thermal Considerations

The LM2594xx is available in two packages: an 8-pin through-hole PDIP and an 8-pin surface-mount SOIC. Both

packages are molded plastic with a copper lead frame. When the package is soldered to the printed-circuit board

(PCB), the copper and the board are the heat sink for the LM2594 and the other heat producing components.

For best thermal performance, wide copper traces must be used and all ground and unused pins must be

soldered to generous amounts of PCB copper, such as a ground plane (one exception to this is the output

(switch pin, which must not have large areas of copper). Large areas of copper provide the best transfer of heat

(lower thermal resistance) to the surrounding air, and even double-sided or multilayer boards provide a better

heat path to the surrounding air. Unless power levels are small, sockets are not recommended because of the

added thermal resistance it adds and the resultant higher junction temperatures.

Package thermal resistance and junction temperature rise numbers are all approximate, and there are many

factors that affects the junction temperature. Some of these factors include board size, shape, thickness,

position, location, and even board temperature. Other factors are trace width, 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.

Furthermore, some of these components such as the catch diode adds 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 could either act as a heat sink taking heat away from the board, or it could add heat to the board.

Circuit Data for Temperature Rise Curve (8-Pin PDIP)

Capacitors Through hole electrolytic

Inductor Through hole, Schott, 100 μH

Diode Through hole, 1-A, 40-V, Schottky

PCB 4 square inches single sided 2 oz. copper (0.0028″)

Figure 40. Junction Temperature Rise, 8-Pin PDIP

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SNVS118E –DECEMBER 1999–REVISED MAY 2020

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Thermal Considerations (continued)

Circuit Data for Temperature Rise Curve

(Surface Mount)

Capacitors Surface mount tantalum, molded Dsize

Inductor Surface mount, Coilcraft DO33, 100 μH

Diode Surface mount, 1-A, 40-V, Schottky

PCB 4 square inches single sided 2 oz. copper (0.0028″)

Figure 41. Junction Temperature Rise, 8-Pin SOIC

Figure 40 and Figure 41 show the LM2594 junction temperature rise above ambient temperature with a 500-mA

load for various input and output voltages. This data was taken with the circuit operating as a buck switcher with

all components mounted on a PCB to simulate the junction temperature under actual operating conditions. This

curve is typical, and can be used for a quick check on the maximum junction temperature for various conditions,

but keep in mind that there are many factors that can affect the junction temperature.

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12 Device and Documentation Support

12.1 Related Links

The table below lists quick access links. Categories include technical documents, support and community

resources, tools and software, and quick access to sample or buy.

Table 8. Related Links

PARTS PRODUCT FOLDER SAMPLE & BUY TECHNICAL

DOCUMENTS TOOLS &

SOFTWARE SUPPORT &

COMMUNITY

LM2594 Click here Click here Click here Click here Click here

LM2594HV Click here Click here Click here Click here Click here

12.2 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.

12.3 Trademarks

E2E is a trademark of Texas Instruments.

SIMPLE SWITCHER is a registered trademark of Texas Instruments.

All other trademarks are the property of their respective owners.

12.4 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.

12.5 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.

PACKAGE OPTION ADDENDUM

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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

LM2594HVM-12/NOPB ACTIVE SOIC D 8 95 Green (RoHS

& no Sb/Br) SN Level-1-260C-UNLIM -40 to 125 2594H

M-12

LM2594HVM-3.3/NOPB ACTIVE SOIC D 8 95 Green (RoHS

& no Sb/Br) SN Level-1-260C-UNLIM -40 to 125 2594H

M-3.3

LM2594HVM-5.0 NRND SOIC D 8 95 TBD Call TI Call TI -40 to 125 2594H

M-5.0

LM2594HVM-5.0/NOPB ACTIVE SOIC D 8 95 Green (RoHS

& no Sb/Br) SN Level-1-260C-UNLIM -40 to 125 2594H

M-5.0

LM2594HVM-ADJ NRND SOIC D 8 95 TBD Call TI Call TI -40 to 125 2594H

M-ADJ

LM2594HVM-ADJ/NOPB ACTIVE SOIC D 8 95 Green (RoHS

& no Sb/Br) SN Level-1-260C-UNLIM -40 to 125 2594H

M-ADJ

LM2594HVMX-12/NOPB ACTIVE SOIC D 8 2500 Green (RoHS

& no Sb/Br) SN Level-1-260C-UNLIM -40 to 125 2594H

M-12

LM2594HVMX-3.3/NOPB ACTIVE SOIC D 8 2500 Green (RoHS

& no Sb/Br) SN Level-1-260C-UNLIM -40 to 125 2594H

M-3.3

LM2594HVMX-5.0/NOPB ACTIVE SOIC D 8 2500 Green (RoHS

& no Sb/Br) SN Level-1-260C-UNLIM -40 to 125 2594H

M-5.0

LM2594HVMX-ADJ/NOPB ACTIVE SOIC D 8 2500 Green (RoHS

& no Sb/Br) SN Level-1-260C-UNLIM -40 to 125 2594H

M-ADJ

LM2594HVN-12/NOPB ACTIVE PDIP P 8 40 Green (RoHS

& no Sb/Br) SN Level-1-NA-UNLIM -40 to 125 LM2594HV

N-12 P+

LM2594HVN-3.3/NOPB ACTIVE PDIP P 8 40 Green (RoHS

& no Sb/Br) Call TI | SN Level-1-NA-UNLIM -40 to 125 LM2594HV

N-3.3 P+

LM2594HVN-5.0/NOPB ACTIVE PDIP P 8 40 Green (RoHS

& no Sb/Br) Call TI | SN Level-1-NA-UNLIM -40 to 125 LM2594HV

N-5.0 P+

LM2594HVN-ADJ/NOPB ACTIVE PDIP P 8 40 Green (RoHS

& no Sb/Br) Call TI | SN Level-1-NA-UNLIM -40 to 125 LM2594HV

N-ADJ P+

LM2594M-12/NOPB ACTIVE SOIC D 8 95 Green (RoHS

& no Sb/Br) SN Level-1-260C-UNLIM -40 to 125 2594

M-12

LM2594M-3.3 NRND SOIC D 8 95 TBD Call TI Call TI -40 to 125 2594

M-3.3

LM2594M-3.3/NOPB ACTIVE SOIC D 8 95 Green (RoHS

& no Sb/Br) SN Level-1-260C-UNLIM -40 to 125 2594

M-3.3

PACKAGE OPTION ADDENDUM

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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

LM2594M-5.0 NRND SOIC D 8 95 TBD Call TI Call TI -40 to 125 2594

M-5.0

LM2594M-5.0/NOPB ACTIVE SOIC D 8 95 Green (RoHS

& no Sb/Br) SN Level-1-260C-UNLIM -40 to 125 2594

M-5.0

LM2594M-ADJ/NOPB ACTIVE SOIC D 8 95 Green (RoHS

& no Sb/Br) SN Level-1-260C-UNLIM -40 to 125 2594

M-ADJ

LM2594MX-12/NOPB ACTIVE SOIC D 8 2500 Green (RoHS

& no Sb/Br) SN Level-1-260C-UNLIM -40 to 125 2594

M-12

LM2594MX-3.3/NOPB ACTIVE SOIC D 8 2500 Green (RoHS

& no Sb/Br) SN Level-1-260C-UNLIM -40 to 125 2594

M-3.3

LM2594MX-5.0/NOPB ACTIVE SOIC D 8 2500 Green (RoHS

& no Sb/Br) SN Level-1-260C-UNLIM -40 to 125 2594

M-5.0

LM2594MX-ADJ/NOPB ACTIVE SOIC D 8 2500 Green (RoHS

& no Sb/Br) SN Level-1-260C-UNLIM -40 to 125 2594

M-ADJ

LM2594N-12/NOPB ACTIVE PDIP P 8 40 Green (RoHS

& no Sb/Br) Call TI | SN Level-1-NA-UNLIM -40 to 125 LM2594N

-12 P+

LM2594N-3.3/NOPB ACTIVE PDIP P 8 40 Green (RoHS

& no Sb/Br) Call TI | SN Level-1-NA-UNLIM -40 to 125 LM2594N

-3.3 P+

LM2594N-5.0/NOPB ACTIVE PDIP P 8 40 Green (RoHS

& no Sb/Br) Call TI | SN Level-1-NA-UNLIM -40 to 125 LM2594N

-5.0 P+

LM2594N-ADJ/NOPB ACTIVE PDIP P 8 40 Green (RoHS

& no Sb/Br) Call TI | SN Level-1-NA-UNLIM -40 to 125 LM2594N

-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) 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.

PACKAGE OPTION ADDENDUM

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Addendum-Page 3

(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/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

LM2594HVMX-12/NOPB SOIC D 8 2500 330.0 12.4 6.5 5.4 2.0 8.0 12.0 Q1

LM2594HVMX-3.3/NOPB SOIC D 8 2500 330.0 12.4 6.5 5.4 2.0 8.0 12.0 Q1

LM2594HVMX-5.0/NOPB SOIC D 8 2500 330.0 12.4 6.5 5.4 2.0 8.0 12.0 Q1

LM2594HVMX-ADJ/NOPB SOIC D 8 2500 330.0 12.4 6.5 5.4 2.0 8.0 12.0 Q1

LM2594MX-12/NOPB SOIC D 8 2500 330.0 12.4 6.5 5.4 2.0 8.0 12.0 Q1

LM2594MX-3.3/NOPB SOIC D 8 2500 330.0 12.4 6.5 5.4 2.0 8.0 12.0 Q1

LM2594MX-5.0/NOPB SOIC D 8 2500 330.0 12.4 6.5 5.4 2.0 8.0 12.0 Q1

LM2594MX-ADJ/NOPB SOIC D 8 2500 330.0 12.4 6.5 5.4 2.0 8.0 12.0 Q1

PACKAGE MATERIALS INFORMATION

www.ti.com 7-May-2020

Pack Materials-Page 1

*All dimensions are nominal

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

LM2594HVMX-12/NOPB SOIC D 8 2500 367.0 367.0 35.0

LM2594HVMX-3.3/NOPB SOIC D 8 2500 367.0 367.0 35.0

LM2594HVMX-5.0/NOPB SOIC D 8 2500 367.0 367.0 35.0

LM2594HVMX-ADJ/NOPB SOIC D 8 2500 367.0 367.0 35.0

LM2594MX-12/NOPB SOIC D 8 2500 367.0 367.0 35.0

LM2594MX-3.3/NOPB SOIC D 8 2500 367.0 367.0 35.0

LM2594MX-5.0/NOPB SOIC D 8 2500 367.0 367.0 35.0

LM2594MX-ADJ/NOPB SOIC D 8 2500 367.0 367.0 35.0

PACKAGE MATERIALS INFORMATION

www.ti.com 7-May-2020

Pack Materials-Page 2

www.ti.com

PACKAGE OUTLINE

.228-.244 TYP

[5.80-6.19]

.069 MAX

[1.75]

6X .050

[1.27]

8X .012-.020

[0.31-0.51]

.150

[3.81]

.005-.010 TYP

[0.13-0.25]

0 - 8 .004-.010

[0.11-0.25]

.010

[0.25]

.016-.050

[0.41-1.27]

4X (0 -15 )

.189-.197

[4.81-5.00]

NOTE 3

B .150-.157

[3.81-3.98]

NOTE 4

4X (0 -15 )

(.041)

[1.04]

SOIC - 1.75 mm max heightD0008A

SMALL OUTLINE INTEGRATED CIRCUIT

4214825/C 02/2019

NOTES:

1. Linear dimensions are in inches [millimeters]. Dimensions in parenthesis are for reference only. Controlling dimensions are in inches.

Dimensioning and tolerancing per ASME Y14.5M.

2. This drawing is subject to change without notice.

3. This dimension does not include mold flash, protrusions, or gate burrs. Mold flash, protrusions, or gate burrs shall not

exceed .006 [0.15] per side.

4. This dimension does not include interlead flash.

5. Reference JEDEC registration MS-012, variation AA.

.010 [0.25] C A B

PIN 1 ID AREA

SEATING PLANE

.004 [0.1] C

SEE DETAIL A

DETAIL A

TYPICAL

SCALE 2.800

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EXAMPLE BOARD LAYOUT

.0028 MAX

[0.07]

ALL AROUND

.0028 MIN

[0.07]

ALL AROUND

(.213)

[5.4]

6X (.050 )

[1.27]

8X (.061 )

[1.55]

8X (.024)

[0.6]

(R.002 ) TYP

[0.05]

SOIC - 1.75 mm max heightD0008A

SMALL OUTLINE INTEGRATED CIRCUIT

4214825/C 02/2019

NOTES: (continued)

6. Publication IPC-7351 may have alternate designs.

7. Solder mask tolerances between and around signal pads can vary based on board fabrication site.

METAL SOLDER MASK

OPENING

NON SOLDER MASK

DEFINED

SOLDER MASK DETAILS

EXPOSED

METAL

OPENING

SOLDER MASK METAL UNDER

SOLDER MASK

DEFINED

EXPOSED

METAL

LAND PATTERN EXAMPLE

EXPOSED METAL SHOWN

SCALE:8X

SYMM

SEE

DETAILS

SYMM

www.ti.com

EXAMPLE STENCIL DESIGN

8X (.061 )

[1.55]

8X (.024)

[0.6]

6X (.050 )

[1.27] (.213)

[5.4]

(R.002 ) TYP

[0.05]

SOIC - 1.75 mm max heightD0008A

SMALL OUTLINE INTEGRATED CIRCUIT

4214825/C 02/2019

NOTES: (continued)

8. Laser cutting apertures with trapezoidal walls and rounded corners may offer better paste release. IPC-7525 may have alternate

design recommendations.

9. Board assembly site may have different recommendations for stencil design.

SOLDER PASTE EXAMPLE

BASED ON .005 INCH [0.125 MM] THICK STENCIL

SCALE:8X

SYMM

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