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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.

LM2675

SNVS129F –MAY 2004–REVISED JUNE 2016

LM2675 SIMPLE SWITCHER

Power Converter High Efficiency

1-A Step-Down Voltage Regulator

1 Features

1• Efficiency up to 96%

• Available in 8-Pin SOIC, PDIP, and 16-Pin WSON

Package

• Requires only 5 External Components

• 3.3-V, 5-V, 12-V, and Adjustable Output Versions

• Adjustable Version Output Voltage Range: 1.21 V

to 37 V

• ±1.5% Maximum Output Voltage Tolerance Over

Line and Load Conditions

• Ensured 1-A Output Load Current

• Wide Input Voltage Range: 8 V to 40 V

• 260-kHz Fixed Frequency Internal Oscillator

• TTL Shutdown Capability, Low-Power Standby

Mode

• Thermal Shutdown and Current Limit Protection

2 Applications

• Simple High Efficiency (>90%) Step-Down (Buck)

Regulator

• Efficient Preregulator for Linear Regulators

• Positive-to-Negative Converter

3 Description

The LM2675 series of regulators are monolithic

integrated DC-DC converter circuits built with a

LMDMOS process. These regulators provide all the

active functions for a step-down (buck) switching

regulator, capable of driving a 1-A 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.

Requiring a minimum number of external

components, these regulators are simple to use and

include patented internal frequency compensation

and a fixed frequency oscillator.

The LM2675 series operates at a switching frequency

of 260 kHz, thus allowing smaller-sized filter

components than what would be needed with lower

frequency switching regulators. Because of its very

high efficiency (>90%), the copper traces on the

printed-circuit board are the only heat sinking needed.

Device Information(1)

PART NUMBER PACKAGE BODY SIZE (NOM)

LM2675 SOIC (8) 5.00 mm × 6.20 mm

PDIP (8) 10.16 mm × 6.60 mm

WSON (16) 5.00 mm × 5.00 mm

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

the end of the data sheet.

Typical Application

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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

7.11 Typical Characteristics – Fixed Output Voltage

Versions..................................................................... 9

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

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

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

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

8.4 Device Functional Modes........................................ 11

9 Application and Implementation ........................ 12

9.1 Application Information............................................ 12

9.2 Typical Application.................................................. 13

10 Power Supply Recommendations ..................... 24

11 Layout................................................................... 25

11.1 Layout Guidelines ................................................. 25

11.2 Layout Examples................................................... 25

12 Device and Documentation Support................. 27

12.1 Documentation Support ........................................ 27

12.2 Receiving Notification of Documentation Updates 27

12.3 Community Resources.......................................... 27

12.4 Trademarks........................................................... 27

12.5 Electrostatic Discharge Caution............................ 27

12.6 Glossary................................................................ 27

13 Mechanical, Packaging, and Orderable

Information........................................................... 27

4 Revision History

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

Changes from Revision E (June 2005) to Revision F 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

• Deleted all instances of the computer design software LM267X Made Simple (version 6.0)................................................ 1

Not to scale

DAP

1CB 16 VSW

2NC 15 VSW

3NC 14 VIN

4NC 13 NC

5NC 12 GND

6NC 11 GND

7NC 10 NC

8FB 9 ON/OFF

Not to scale

1CB 8 VSW

2NC 7 VIN

3NC 6 GND

4FB 5 ON/OFF

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5 Description (continued)

A family of standard inductors for use with the LM2675 are available from several different manufacturers. This

feature greatly simplifies the design of switch-mode power supplies using these advanced ICs. Also included in

the data sheet are selector guides for diodes and capacitors designed to work in switch-mode power supplies.

Other features include ±1.5%-tolerance on output voltage within specified input voltages and output load

conditions, and ±10% on the oscillator frequency. External shutdown is included, featuring typically 50-μA stand-

by current. The output switch includes current limiting, as well as thermal shutdown for full protection under fault

conditions.

6 Pin Configuration and Functions

D or P Package

8-Pin SOIC or PDIP

Top View NHN Package

16-Pin WSON

Top View

Pin Functions

PIN I/O DESCRIPTION

NAME D, P NHN

CB1 1 I Boot-strap capacitor connection for high-side driver. Connect a high quality

470-nF capacitor from CBto VSW pin.

FB 4 8 I Feedback sense input pin. Connect to the midpoint of feedback divider to set

VOUT for adjustable version or connect this pin directly to the output capacitor

for a fixed output version.

GND 6 11, 12 — Power ground pins. Connect to system ground. Ground pins of CIN and COUT.

Path to CIN must be as short as possible.

NC 2, 3 2, 3, 4, 5,

6, 7, 10, 13 — No connect pins.

ON/OFF 5 9 I Enable input to the voltage regulator. High = ON and low = OFF. Pull this pin

high or float to enable the regulator.

VIN 7 14 I Supply input pin to collector pin of high side FET. Connect to power supply and

input bypass capacitors CIN. Path from VIN pin to high frequency bypass CIN

and GND must be as short as possible.

VSW 8 15, 16 O Source pin of the internal High Side FET. This is a switching node. Attached this

pin to an inductor and the cathode of the external diode.

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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, contact the Texas Instruments Sales Office/ Distributors for availability and

specifications.

7 Specifications

7.1 Absolute Maximum Ratings

over recommended operating junction temperature range of –40°C to 125°C (unless otherwise noted)(1)(2)

MIN MAX UNIT

Supply voltage 45 V

ON/OFF pin voltage, VSH –0.1 6 V

Switch voltage to ground –1 V

Boost pin voltage VSW + 8 V

Feedback pin voltage, VFB –0.3 14 V

Power dissipation Internally limited

Lead temperature D package Vapor phase (60 s) 215

°C

Infrared (15 s) 220

P package (soldering, 10 s) 260

NHN package See AN-1187

Maximum junction temperature, TJ150 °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 1.5-kΩresistor 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

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

Supply voltage 6.5 40 V

TJTemperature –40 125 °C

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

report.

(2) Thermal resistances were simulated on 4-layer JEDEC board.

(3) Junction-to-ambient thermal resistance with approximately 1 square inch of printed-circuit board copper surrounding the leads.

Additional copper area lowers thermal resistance further. See Application Information in the application note accompanying this data

sheet. The value RθJA for the WSON (NHN) package is specifically dependent on PCB trace area, trace material, and the number of

layers and thermal vias. For improved thermal resistance and power dissipation for the WSON package, refer to AN-1187 Leadless

Leadframe Package (LLP).

7.4 Thermal Information

THERMAL METRIC(1)(2) LM2675

UNITSOIC (D) PDIP (P) NHN (WSON)

8 PINS 8 PINS 16 PINS

RθJA Junction-to-ambient thermal resistance(3) 105 95 — °C/W

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

RθJB Junction-to-board thermal resistance — — — °C/W

ψJT Junction-to-top characterization parameter — — — °C/W

ψJB Junction-to-board characterization parameter — — — °C/W

RθJC(bot) Junction-to-case (bottom) thermal resistance — — — °C/W

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

switching regulator performance. When the LM2675 is used as shown in Figure 19 test circuits, system performance is as specified by

the system parameters section of Electrical Characteristics.

(2) All limits specified at room temperature and at temperature extremes. All room temperature limits are 100% production tested. All limits

at temperature extremes are specified through correlation using standard Statistical Quality Control (SQC) methods. All limits are used

to calculate Average Outgoing Quality Level (AOQL).

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

7.5 Electrical Characteristics – 3.3 V

TJ= 25°C (unless otherwise noted; see Figure 19)(1)

PARAMETER TEST CONDITIONS MIN(2) TYP(3) MAX(2) UNIT

VOUT Output voltage VIN = 8 V to 40 V, ILOAD = 20 mA to 1 A TJ= 25°C 3.251 3.3 3.35

TJ= –40°C to 125°C 3.201 3.399

VIN = 6.5 V to 40 V,

ILOAD = 20 mA to 500 mA TJ= 25°C 3.251 3.3 3.35

TJ= –40°C to 125°C 3.201 3.399

ηEfficiency VIN = 12 V, ILOAD = 1 A 86%

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

switching regulator performance. When the LM2675 is used as shown in Figure 19 test circuits, system performance is as specified by

the system parameters section of Electrical Characteristics.

(2) All limits specified at room temperature and at temperature extremes. All room temperature limits are 100% production tested. All limits

at temperature extremes are specified through correlation using standard Statistical Quality Control (SQC) methods. All limits are used

to calculate Average Outgoing Quality Level (AOQL).

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

7.6 Electrical Characteristics – 5 V

TJ= 25°C (unless otherwise noted; see Figure 19)(1)

PARAMETER TEST CONDITIONS MIN(2) TYP(3) MAX(2) UNIT

VOUT Output voltage VIN = 8 V to 40 V, ILOAD = 20 mA to 1 A TJ= 25°C 4.925 5 5.075

TJ= –40°C to 125°C 4.85 5.15

VIN = 6.5 V to 40 V,

ILOAD = 20 mA to 500 mA TJ= 25°C 4.925 5 5.075

TJ= –40°C to 125°C 4.85 5.15

ηEfficiency VIN = 12 V, ILOAD = 1 A 90%

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

switching regulator performance. When the LM2675 is used as shown in Figure 19 test circuits, system performance is as specified by

the system parameters section of Electrical Characteristics.

(2) All limits specified at room temperature and at temperature extremes. All room temperature limits are 100% production tested. All limits

at temperature extremes are specified through correlation using standard Statistical Quality Control (SQC) methods. All limits are used

to calculate Average Outgoing Quality Level (AOQL).

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

7.7 Electrical Characteristics – 12 V

TJ= 25°C (unless otherwise noted; see Figure 19)(1)

PARAMETER TEST CONDITIONS MIN(2) TYP(3) MAX(2) UNIT

VOUT Output voltage VIN = 15 V to 40 V, ILOAD = 20 mA to 1 A TJ= 25°C 11.82 12 12.18 V

TJ= –40°C to 125°C 11.64 12.36

ηEfficiency VIN = 24 V, ILOAD = 1 A 94%

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

switching regulator performance. When the LM2675 is used as shown in Figure 19 test circuits, system performance is as specified by

the system parameters section of Electrical Characteristics.

(2) All limits specified at room temperature and at temperature extremes. All room temperature limits are 100% production tested. All limits

at temperature extremes are specified through correlation using standard Statistical Quality Control (SQC) methods. All limits are used

to calculate Average Outgoing Quality Level (AOQL).

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

7.8 Electrical Characteristics – Adjustable

TJ= 25°C (unless otherwise noted; see Figure 19)(1)

PARAMETER TEST CONDITIONS MIN(2) TYP(3) MAX(2) UNIT

VFB Feedback

voltage

VIN = 8 V to 40 V, ILOAD = 20 mA to 1 A,

VOUT programmed for 5 V (see Figure 19)TJ= 25°C 1.192 1.21 1.228

TJ= –40°C to 125°C 1.174 1.246

VIN = 6.5 V to 40 V, ILOAD = 20 mA to 500

mA, VOUT programmed for 5 V (see

Figure 19)

TJ= 25°C 1.192 1.21 1.228

TJ= –40°C to 125°C 1.174 1.246

ηEfficiency VIN = 12 V, ILOAD = 1 A 90%

(1) All limits specified at room temperature and at temperature extremes. All room temperature limits are 100% production tested. All limits

at temperature extremes are specified through 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.

7.9 Electrical Characteristics – All Output Voltage Versions

TJ= 25°C, VIN = 12 V for the 3.3 V, 5 V, and adjustable versions, and VIN = 24 V for the 12 V version, and ILOAD = 100 mA

(unless otherwise noted)

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

IQQuiescent current VFEEDBACK = 8 V for 3.3 V, 5 V, and adjustable versions 2.5 3.6 mA

VFEEDBACK = 15 V for 12 V versions 2.5 mA

ISTBY Standby quiescent current ON/OFF Pin = 0 V TJ= 25°C 50 100 μA

TJ= –40°C to 125°C 150

ICL Current limit TJ= 25°C 1.25 1.55 2.1 A

TJ= –40°C to 125°C 1.2 2.2

ILOutput leakage current VSWITCH = 0 V, ON/OFF Pin = 0 V, VIN = 40 V 1 25 μA

VSWITCH =−1 V, ON/OFF Pin = 0 V 6 15 mA

RDS(ON) Switch on-resistance ISWITCH = 1 A TJ= 25°C 0.25 0.3 Ω

TJ= –40°C to 125°C 0.5

fOOscillator frequency Measured at switch pin TJ= 25°C 260 kHz

TJ= –40°C to 125°C 225 275

D Minimum duty cycle TJ= 25°C 95%

TJ= –40°C to 125°C 0%

IBIAS Feedback bias current VFEEDBACK = 1.3 V, adjustable version only 85 nA

VS/D ON/OFF pin voltage TJ= 25°C 1.4 V

TJ= –40°C to 125°C 0.8 2

IS/D ON/OFF pin current ON/OFF Pin = 0 V TJ= 25°C 20 μA

TJ= –40°C to 125°C 7 37

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7.10 Typical Characteristics

Figure 1. Normalized Output Voltage Figure 2. Line Regulation

Figure 3. Efficiency Figure 4. Drain-to-Source Resistance

Figure 5. Switch Current Limit Figure 6. Operating Quiescent Current

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Typical Characteristics (continued)

Figure 7. Standby Quiescent Current Figure 8. ON/OFF Threshold Voltage

Figure 9. ON/OFF Pin Current (Sourcing) Figure 10. Switching Frequency

Figure 11. Feedback Pin Bias Current Figure 12. Peak Switch Current

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Typical Characteristics (continued)

Figure 13. Dropout Voltage, 3.3-V Option Figure 14. Dropout Voltage, 5-V Option

7.11 Typical Characteristics – Fixed Output Voltage Versions

see Figure 19

VSW pin voltage, 10 V/div VIN = 20 V, VOUT = 5 V,

Inductor current, 0.5 A/div ILOAD = 1 A, L = 47 μH,

Output ripple voltage,

20 mV/div AC-coupled COUT = 68 μF,

COUTESR = 50 mΩ

Figure 15. Continuous Mode Switching Waveforms,

Horizontal Time Base: 1 μs/div

VSW pin voltage, 10 V/div VIN = 20 V, VOUT = 5 V,

Inductor current, 0.5 A/div ILOAD = 300 mA, L = 15 μH,

Output ripple voltage,

20 mV/div AC-coupled COUT = 68 μF (2×),

COUTESR = 25 mΩ

Figure 16. Discontinuous Mode Switching Waveforms,

Horizontal Time Base: 1 μs/div

Output voltage, 100 mV/div, VIN = 20 V, VOUT = 5 V,

AC-coupled ILOAD = 1 A, L = 47 μH,

Load current: 200-mA

to 1-A load pulse COUT = 68 μF,

COUTESR = 50 mΩ

Figure 17. Load Transient Response for Continuous Mode,

Horizontal Time Base: 50 μs/div

Output voltage, 100 mV/div, VIN = 20 V, VOUT = 5 V,

AC-coupled L = 47 μH,

Load current: 100-mA

to 400-mA load pulse COUT = 68 μF (2×),

COUTESR = 50 mΩ

Figure 18. Load Transient Response for Discontinuous

Mode, Horizontal Time Base: 200 μs/div

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8 Detailed Description

8.1 Overview

The LM2675 provides all of the active functions required for a step-down (buck) switching regulator. The internal

power switch is a DMOS power MOSFET to provide power supply designs with high current capability, up to 1 A,

and highly efficient operation. The LM2675 is part of the SIMPLE SWITCHER®family of power converters. A

complete design uses a minimum number of external components, which have been predetermined from a

variety of manufacturers. Using either this data sheet or TI's WEBENCH® design tool, a complete switching

power supply can be designed quickly. See LM2670 SIMPLE SWITCHER®High Efficiency 3A Step-Down

Voltage Regulator with Sync for additional application information.

8.2 Functional Block Diagram

8.3 Feature Description

8.3.1 Adjustable Output Voltage

The voltage regulation loop in the LM2675 regulates output voltage by maintaining the voltage on FB pin (VFB) to

be the same as the internal REF voltage (VREF). A resistor divider pair is needed to program the ratio from output

voltage VOUT to VFB. The resistor is connected from the VOUT of the LM2674 to ground with the mid-point

connecting to the FB pin. The voltage reference system produces a precise voltage reference over temperature.

The internal REF voltage is typically 1.21 V. To program the output voltage of the LM2675 to be a certain value

VOUT, R1 can be calculated with a selected R2. See Programming Output Voltage for adjustable output voltage

typical application. The recommended range for R2 in most application is from 10 kΩto 100 kΩ. If the resistor

divider is not connected properly, output voltage cannot be regulated because the feedback loop is broken. If the

FB pin is shorted to ground, the output voltage is driven close to VIN, because the regulator sees very low

voltage on the FB pin and tries to regulate it. The load connected to the output could be damaged under such a

condition. Do not short FB pin to ground when the LM2675 is enabled. It is important to route the feedback trace

away from the noisy area of the PCB. For more layout recommendations, see Layout.

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8.4 Device Functional Modes

8.4.1 Shutdown Mode

The ON/OFF pin provides electrical ON and OFF control for the LM2674. When the voltage of this pin is lower

than 1.4 V, the device is in shutdown mode. The typical standby current in this mode is 20 μA.

8.4.2 Active Mode

When the voltage of the ON/OFF pin is higher than 1.4 V, the device starts switching and the output voltage rises

until it reaches a normal regulation voltage.

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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

The LM2675 is a step-down DC-DC regulator. The device is typically used to convert a higher DC voltage to a

lower DC voltage with a maximum output current of 1 A. The following design procedure can be used to select

components for the LM2675.

When the output voltage is greater than approximately 6 V, and the duty cycle at minimum input voltage is

greater than approximately 50%, the designer should exercise caution in selection of the output filter

components. When an application designed to these specific operating conditions is subjected to a current limit

fault condition, it may be possible to observe a large hysteresis in the current limit. This can affect the output

voltage of the device until the load current is reduced sufficiently to allow the current limit protection circuit to

reset itself.

Under current limiting conditions, the LM2675 is designed to respond in the following manner:

1. At the moment when the inductor current reaches the current limit threshold, the ON-pulse is immediately

terminated. This happens for any application condition.

2. However, the current limit block is also designed to momentarily reduce the duty cycle to below 50% to avoid

subharmonic oscillations, which could cause the inductor to saturate.

3. Thereafter, once the inductor current falls below the current limit threshold, there is a small relaxation time

during which the duty cycle progressively rises back above 50% to the value required to achieve regulation.

If the output capacitance is sufficiently large, it may be possible that as the output tries to recover, the output

capacitor charging current is large enough to repeatedly re-trigger the current limit circuit before the output has

fully settled. This condition is exacerbated with higher output voltage settings because the energy requirement of

the output capacitor varies as the square of the output voltage (½ CV2), thus requiring an increased charging

current. A simple test to determine if this condition might exist for a suspect application is to apply a short circuit

across the output of the converter, and then remove the shorted output condition. In an application with properly

selected external components, the output recovers smoothly. Practical values of external components that have

been experimentally found to work well under these specific operating conditions are COUT = 47 µF,

L = 22 µH. It should be noted that even with these components, for a device’s current limit of ICLIM, the maximum

load current under which the possibility of the large current limit hysteresis can be minimized is ICLIM/2. For

example, if the input is 24 V and the set output voltage is 18 V, then for a desired maximum current of 1.5 A, the

current limit of the chosen switcher must be confirmed to be at least 3 A. Under extreme overcurrent or short-

circuit conditions, the LM2675 employs frequency foldback in addition to the current limit. If the cycle-by-cycle

inductor current increases above the current limit threshold (due to short circuit or inductor saturation for

example) the switching frequency is automatically reduced to protect the IC. Frequency below 100 kHz is typical

for an extreme short-circuit condition.

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9.2 Typical Application

9.2.1 Fixed Output Voltage Application

CIN = 22-μF, 50-V Tantalum, Sprague 199D Series

COUT = 47-μF, 25-V Tantalum, Sprague 595D Series

D1 = 3.3-A, 50-V Schottky Rectifier, IR 30WQ05F

L1 = 68-μH Sumida #RCR110D-680L

CB= 0.01-μF, 50-V Ceramic

Figure 19. Fixed Output Voltage Schematic

9.2.1.1 Design Requirements

Table 1 lists the design requirements for the fixed output voltage application.

Table 1. Design Parameters

PARAMETER VALUE

Regulated output voltage, VOUT 5 V

Maximum input voltage, VIN(max) 12 V

Maximum load current, ILOAD(max) 1 A

9.2.1.2 Detailed Design Procedure

9.2.1.2.1 Inductor Selection (L1)

Select the correct inductor value selection guide from Figure 21,Figure 22,orFigure 23 (output voltages of

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

selection guide for the 5-V version shown in Figure 22.

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 22, the inductance region intersected by the 12-V

horizontal line and the 1-A vertical line is 33 μH, and the inductor code is L23.

Select an appropriate inductor from the four manufacturer's part numbers listed in Table 2. Each manufacturer

makes a different style of inductor to allow flexibility in meeting various design requirements. The inductance

value required is 33 μH. From the table in Table 2, go to the L23 line and choose an inductor part number from

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

available.

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Table 2. Inductor Manufacturers' Part Numbers

IND.

REF.

DESG.

INDUCTANCE

(μH) CURRENT

(A)

SCHOTT RENCO PULSE ENGINEERING COILCRAFT

THROUGH

HOLE SURFACE

MOUNT THROUGH

HOLE SURFACE

MOUNT THROUGH

HOLE SURFACE

MOUNT SURFACE

MOUNT

L4 68 0.32 67143940 67144310 RL-1284-68-43 RL1500-68 PE-53804 PE-53804-S DO1608-683

L5 47 0.37 67148310 67148420 RL-1284-47-43 RL1500-47 PE-53805 PE-53805-S DO1608-473

L6 33 0.44 67148320 67148430 RL-1284-33-43 RL1500-33 PE-53806 PE-53806-S DO1608-333

L7 22 0.52 67148330 67148440 RL-1284-22-43 RL1500-22 PE-53807 PE-53807-S DO1608-223

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 DO3308-683

L13 47 0.7 67144000 67144380 RL-5470-7 RL1500-47 PE-53813 PE-53813-S DO3308-473

L14 33 0.83 67148340 67148450 RL-1284-33-43 RL1500-33 PE-53814 PE-53814-S DO3308-333

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

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 DO3316-683

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

L23 33 1.4 67144090 67144470 RL-5471-7 — PE-53823 PE-53823-S DO3316-333

L24 22 1.7 67148370 67148480 RL-1283-22-43 — PE-53824 PE-53824-S DO3316-223

L27 220 1 67144110 67144490 RL-5471-2 — PE-53827 PE-53827-S DO5022P-224

L28 150 1.2 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

9.2.1.2.2 Output Capacitor Selection (COUT)

Select an output capacitor from Table 3. Using the output voltage and the inductance value found in the inductor

selection guide, step 1, locate the appropriate capacitor value and voltage rating. The capacitor list contains

through-hole electrolytic capacitors from four different capacitor manufacturers and surface mount tantalum

capacitors from two different capacitor manufacturers. TI recommends using both the manufacturers and the

manufacturer's series that are listed in the table.

Use the 5-V section in Table 3. Choose a capacitor value and voltage rating from the line that contains the

inductance value of 33 μH. The capacitance and voltage rating values corresponding to the 33-μH inductor are

the surface mount and through hole.

Surface mount:

• 68-μF, 10-V Sprague 594D series

• 100-μF, 10-V AVX TPS series

Through hole:

• 68-μF, 10-V Sanyo OS-CON SA series

• 220-μF, 35-V Sanyo MV-GX series

• 220-μF, 35-V Nichicon PL series

• 220-μF, 35-V Panasonic HFQ series

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Table 3. Output Capacitor Table

OUTPUT

VOLTAGE

(V)

INDUCTANCE

(μH)

OUTPUT CAPACITOR

SURFACE MOUNT THROUGH HOLE

SPRAGUE

594D SERIES

(μF/V)

AVX TPS

SERIES

(μF/V)

SANYO OS-CON

SA SERIES

(μF/V)

SANYO MV-GX

SERIES

(μF/V)

NICHICON

PL SERIES

(μF/V)

PANASONIC

HFQ SERIES

(μF/V)

3.3

22 120/6.3 100/10 100/10 330/35 330/35 330/35

33 120/6.3 100/10 68/10 220/35 220/35 220/35

47 68/10 100/10 68/10 150/35 150/35 150/35

68 120/6.3 100/10 100/10 120/35 120/35 120/35

100 120/6.3 100/10 100/10 120/35 120/35 120/35

150 120/6.3 100/10 100/10 120/35 120/35 120/35

22 100/16 100/10 100/10 330/35 330/35 330/35

33 68/10 10010 68/10 220/35 220/35 220/35

47 68/10 100/10 68/10 150/35 150/35 150/35

68 100/16 100/10 100/10 120/35 120/35 120/35

100 100/16 100/10 100/10 120/35 120/35 120/35

150 100/16 100/10 100/10 120/35 120/35 120/35

22 120/20 (2×) 68/20 68/20 330/35 330/35 330/35

33 68/25 68/20 68/20 220/35 220/35 220/35

47 47/20 68/20 47/20 150/35 150/35 150/35

68 47/20 68/20 47/20 120/35 120/35 120/35

100 47/20 68/20 47/20 120/35 120/35 120/35

150 47/20 68/20 47/20 120/35 120/35 120/35

220 47/20 68/20 47/20 120/35 120/35 120/35

9.2.1.2.3 Catch Diode Selection (D1)

In normal operation, the average current of the catch diode is the load current times the catch diode duty cycle,

1-D (D is the switch duty cycle, which is approximately the output voltage divided by the input voltage). The

largest value of the catch diode average current occurs at the maximum load current and maximum input voltage

(minimum D). For normal operation, the catch diode current rating must be at least 1.3 times greater than its

maximum average current. However, 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 LM2675. The most stressful condition

for this diode is a shorted output condition (see Table 4). In this example, a 1-A, 20-V Schottky diode provides

the best performance. If the circuit must withstand a continuous shorted output, TI recommends a Schottky diode

of higher current.

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

fast switching speed and low forward voltage drop, Schottky diodes provide the best performance and efficiency.

This Schottky diode must be located close to the LM2675 using short leads and short printed circuit traces.

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Table 4. Schottky Diode Selection Table

VR1-A DIODES 3-A DIODES

SURFACE MOUNT THROUGH HOLE SURFACE MOUNT THROUGH HOLE

20 V SK12 1N5817 SK32 1N5820

B120 SR102 — SR302

30 V SK13 1N5818 SK33 1N5821

B130 11DQ03 30WQ03F 31DQ03

MBRS130 SR103 — —

40 V

SK14 1N5819 SK34 1N5822

B140 11DQ04 30BQ040 MBR340

MBRS140 SR104 30WQ04F 31DQ04

10BQ040 — MBRS340 SR304

10MQ040 — MBRD340 —

15MQ040 — — —

50 V SK15 MBR150 SK35 MBR350

B150 11DQ05 30WQ05F 31DQ05

10BQ050 SR105 — SR305

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. This capacitor must be located close to the IC using short leads.

In addition, the RMS current rating of the input capacitor must be selected to be at least ½ the DC load current.

The capacitor manufacturer data sheet must be checked to assure that this current rating is not exceeded.

Figure 20 shows typical RMS current ratings for several different aluminum electrolytic capacitor values. A

parallel connection of two or more capacitors may be required to increase the total minimum RMS current rating

to suit the application requirements.

Figure 20. RMS Current Ratings for Low ESR Electrolytic Capacitors (Typical)

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For an aluminum electrolytic capacitor, the voltage rating must be at least 1.25 times the maximum input voltage.

Caution must be exercised if solid tantalum capacitors are used. The tantalum capacitor voltage rating must be

twice the maximum input voltage. Table 3 shows the recommended application voltage for AVX TPS and

Sprague 594D tantalum capacitors. TI also recommends that they be surge current tested by the manufacturer.

The TPS series available from AVX, and the 593D and 594D series from Sprague are all surge current tested.

Another approach to minimize the surge current stresses on the input capacitor is to add a small inductor in

series with the input supply line.

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

maximum input voltage of 12 V, an aluminum electrolytic capacitor with a voltage rating greater than 15 V

(1.25 × VIN) would be needed. The next higher capacitor voltage rating is 16 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 1-A load, a capacitor with a RMS current rating of at least 500 mA is needed. The

curves shown in Figure 20 can be used to select an appropriate input capacitor. From the curves, locate the 16-V

line and note which capacitor values have RMS current ratings greater than 500 mA.

For a through hole design, a 330-μF, 16-V electrolytic capacitor (Panasonic HFQ series, Nichicon PL, Sanyo MV-

GX series or equivalent) would be adequate. Other types or other manufacturers' capacitors can be used

provided the RMS ripple current ratings are adequate. Additionally, for a complete surface mount design,

electrolytic capacitors such as the Sanyo CV-C or CV-BS and the Nichicon WF or UR and the NIC Components

NACZ series could be considered.

For surface-mount designs, solid tantalum capacitors can be used, but caution must be exercised with regard to

the capacitor surge current rating and voltage rating. In this example, checking Table 5, and the Sprague 594D

series data sheet, a Sprague 594D 15-μF, 25-V capacitor is adequate.

Table 5. Sprague 594D

RECOMMENDED APPLICATION VOLTAGE VOLTAGE RATING

85°C RATING

2.5 4

3.3 6.3

5 10

8 16

12 20

18 25

24 35

29 50