TEXAS INSTRUMENTS LM 2671 M5,0 Instructions

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SNVS008L –SEPTEMBER 1998–REVISED JUNE 2016

LM2671 SIMPLE SWITCHER®Power Converter High Efficiency 500-mA

Step-Down Voltage Regulator With Features

LM2671

1 Features

• Efficiency up to 96%

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

• Simple and Easy to Design With

• Requires Only 5 External Components

• Uses Readily Available Standard Inductors

• 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 500-mA Output Load Current

• 0.25-Ω DMOS Output Switch

• Wide Input Voltage Range: 8 V to 40 V

• 260-kHz Fixed Frequency Internal Oscillator

• TTL Shutdown Capability, Low Power Standby Mode

• Soft-Start and Frequency Synchronization

• Thermal Shutdown and Current-Limit Protection

2 Applications

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

• Efficient Preregulator for Linear Regulators

3 Description

The LM2671 series of regulators are monolithic integrated circuits built with a LMDMOS process. These regulators provide all the active functions for a step-down (buck) switching regulator, capable of driving a 500-mA 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, fixed frequency oscillator, external shutdown, soft start, and frequency synchronization.

The LM2671 series operates at a switching frequency of 260 kHz, thus allowing smaller sized filter components than what is required 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 required.

A family of standard inductors for use with the LM2671 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.

Device Information

PART NUMBER PACKAGE BODY SIZE (NOM)

SOIC (8) 4.90 mm × 3.91 mm

LM2674

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

the end of the data sheet.

PDIP (8) 9.81 mm × 6.35 mm WSON (16) 5.00 mm × 5.00 mm

(1)

Typical Application

For fixed output voltage versions

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

LM2671

SNVS008L –SEPTEMBER 1998–REVISED JUNE 2016

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

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

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

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

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

6 Pin Configuration and Functions......................... 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........................................ 11

9 Application and Implementation ........................ 13

9.1 Application Information............................................ 13

9.2 Typical Applications ................................................ 14

10 Power Supply Recommendations ..................... 26

11 Layout................................................................... 27

11.1 Layout Guidelines ................................................. 27

11.2 Layout Examples................................................... 27

12 Device and Documentation Support ................. 28

12.1 Documentation Support ........................................ 28

12.2 Receiving Notification of Documentation Updates 28

12.3 Community Resources.......................................... 28

12.4 Trademarks........................................................... 28

12.5 Electrostatic Discharge Caution............................ 28

12.6 Glossary................................................................ 28

13 Mechanical, Packaging, and Orderable

Information........................................................... 28

13.1 DAP (WSON Package)......................................... 28

4 Revision History

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

Changes from Revision K (April 2013) to Revision L 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 Computer Design Software LM267X Made Simple (Version 6.0).............................................. 1

Changes from Revision J (April 2013) to Revision K Page

• Changed layout of National Data Sheet to TI format ........................................................................................................... 27

Product Folder Links: LM2671

Not to scale

DAP

VSW

VIN

GND

SYNC

GND

ON/OFF

16 15 14 13 12 11 10

Not to scale

1CB 8 VSW

2SS 7 VIN

3SYNC 6 GND

4FB 5 ON/OFF

LM2671

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SNVS008L –SEPTEMBER 1998–REVISED JUNE 2016

5 Description (continued)

Other features include a ensured ±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 standby 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

NAME SOIC, PDIP WSON

I/O DESCRIPTION

CB 1 1 I

SS 2 4 I

SYNC 3 6 I

FB 4 8 I

ON/OFF 5 9 I

VSW 8 15, 16 O

GND 6 11, 12 —

VIN 7 14 I

NC —

2, 3, 5, 7,

10, 13

Pin Functions

Bootstrap capacitor connection for high-side driver. Connect a high-quality, 100-nF capacitor from CB to VSW Pin.

Soft-start Pin. Connect a capacitor from this pin to GND to control the output voltage ramp. If the feature not desired, the pin can be left floating.

This input allows control of the switching clock frequency. If left open-circuited the regulator is switched at the internal oscillator frequency, typically 260 kHz.

Feedback sense input pin. Connect to the midpoint of feedback divider to set VOUT for ADJ version or connect this pin directly to the output capacitor for a fixed output version.

Enable input to the voltage regulator. High = ON and low = OFF. Pull this pin high or float to enable the regulator

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.

Power ground pins. Connect to system ground. Ground pins of CINand C Path to CINmust be as short as possible.

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 C and GND must be as short as possible.

— No connect pins

NHN Package 16-Pin WSON

Top View

Connect DAP to pin 11 and 12

OUT

Product Folder Links: LM2671

LM2671

SNVS008L –SEPTEMBER 1998–REVISED JUNE 2016

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7 Specifications

7.1 Absolute Maximum Ratings

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

Supply voltage 45 V ON/OFF pin voltage, V Switch voltage to ground –1 V Boost pin voltage VSW+ 8 V Feedback pin voltage, V Power dissipation Internally Limited

Lead temperature

Maximum junction temperature 150 °C Storage temperature, T

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

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

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

specifications.

D package

Vapor phase (60 s) 215

Infrared (15 s) 220 P package (soldering, 10 s) 260 WSON package See AN-1187

stg

(1)(2)

MIN MAX UNIT

−0.1 6 V

−0.3 14 V

°C

−65 150 °C

7.2 ESD Ratings

VALUE UNIT

(ESD)

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

(1)(2)

±2000 V

(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-kΩ resistor into each pin.

7.3 Recommended Operating Conditions

MIN MAX UNIT

Supply voltage 6.5 40 V Junction temperature, T

–40 125 °C

7.4 Thermal Information

LM2674

THERMAL METRIC

θJA

Junction-to-ambient thermal resistance

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

report.

(2) 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. The value R area, trace material, and the number of layers and thermal vias. For improved thermal resistance and power dissipation for the WSON package, see AN-1187 Leadless Leadframe Package (LLP).

(1)

UNITD (SOIC) P (PDIP) NHN (WSON)

8 PINS 8 PINS 16 PINS

(2)

for the WSON (NHN) package is specifically dependent on PCB trace

θJA

105 95 — °C/W

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LM2671

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SNVS008L –SEPTEMBER 1998–REVISED JUNE 2016

7.5 Electrical Characteristics – 3.3 V

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

PARAMETER TEST CONDITIONS MIN

SYSTEM PARAMETERS

Output voltage

OUT

η Efficiency VIN= 12 V, I

(3)

VIN= 8 V to 40 V, I

= 20 mA to 500 mA

LOAD

VIN= 6.5 V to 40 V, I

= 20 mA to 250 mA

LOAD

TJ= 25°C 3.251 3.3 3.35 Over full operating temperature

range TJ= 25°C 3.251 3.3 3.35 Over full operating temperature

range

= 500 mA 86%

(1)

3.201 3.399

(1) All room temperature limits are 100% production tested. All limits at temperature extremes are ensured 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. (3) External components such as the catch diode, inductor, input and output capacitors, and voltage programming resistors can affect

switching regulator performance. When the LM2671 is used as shown in Figure 15 and Figure 21 test circuits, system performance is as

specified by the system parameters section of the Electrical Characteristics.

TYP

(2)

MAX

(1)

7.6 Electrical Characteristics – 5 V

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

PARAMETER TEST CONDITIONS MIN

SYSTEM PARAMETERS

Output voltage

OUT

η Efficiency VIN= 12 V, I

(3)

VIN= 8 V to 40 V, I

= 20 mA to 500 mA

LOAD

VIN= 6.5 V to 40 V, I

= 20 mA to 250 mA

LOAD

TJ= 25°C 4.925 5 5.075 Over full operating temperature

range TJ= 25°C 4.925 5 5.075 Over full operating temperature

range

= 500 mA 90%

(1)

4.85 5.15

(1) All room temperature limits are 100% production tested. All limits at temperature extremes are ensured through correlation using

switching regulator performance. When the LM2671 is used as shown in Figure 15 and Figure 21 test circuits, system performance is as

specified by the system parameters section of the Electrical Characteristics.

TYP

(2)

MAX

(1)

UNIT

7.7 Electrical Characteristics – 12 V

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

PARAMETER TEST CONDITIONS MIN

SYSTEM PARAMETERS

Output voltage

OUT

η Efficiency VIN= 24 V, I

(3)

VIN= 15 V to 40 V, I

= 20 mA to 500 mA

LOAD

TJ= 25°C 11.82 12 12.18 Over full operating

temperature range

= 500 mA 94%

(1)

11.64 12.36

(1) All room temperature limits are 100% production tested. All limits at temperature extremes are ensured through correlation using

switching regulator performance. When the LM2671 is used as shown in Figure 15 and Figure 21 test circuits, system performance is as

specified by the system parameters section of the Electrical Characteristics.

Product Folder Links: LM2671

TYP

(2)

MAX

(1)

UNIT

LM2671

SNVS008L –SEPTEMBER 1998–REVISED JUNE 2016

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7.8 Electrical Characteristics – Adjustable

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

PARAMETER TEST CONDITIONS MIN

SYSTEM PARAMETERS

Feedback

voltage

η Efficiency VIN= 12 V, I

(3)

VIN= 8 V to 40 V, I

= 20 mA to 500 mA

LOAD

programmed for 5 V

OUT

VIN= 6.5 V to 40 V, I

= 20 mA to 250 mA

LOAD

programmed for 5 V

OUT

LOAD

TJ= 25°C 1.192 1.21 1.228 Over full operating

temperature range TJ= 25°C 1.192 1.21 1.228 Over full operating

temperature range

= 500 mA 90%

(1)

1.174 1.246

(1) All room temperature limits are 100% production tested. All limits at temperature extremes are ensured through correlation using

switching regulator performance. When the LM2671 is used as shown in Figure 15 and Figure 21 test circuits, system performance is as

specified by the system parameters section of the Electrical Characteristics.

TYP

(2)

MAX

(1)

UNIT

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 versions and VIN= 24 V for the 12-V version, and I

DEVICE PARAMETERS

STBY

DS(ON)

BIAS

S/D

SYNC

= 100 mA (unless otherwise noted).

LOAD

PARAMETERS TEST CONDITIONS MIN TYP MAX UNIT

Quiescent current

Standby quiescent current ON/OFF pin = 0 V

Current limit

Output leakage current

Switch ON-resistance I

Oscillator frequency Measured at switch pin

Maximum duty cycle 95% Minimum duty cycle 0% Feedback bias current V

ON/OFF pin voltage thresholds

ON/OFF pin current ON/OFF pin = 0 V

Synchronization frequency V Synchronization threshold voltage 1.4 V

Soft-start voltage

Soft-start current

for 3.3-V, 5-V, and adjustable versions V

for 12-V versions

TJ= 25°C 0.62 0.8 1.2 Over full operating temperature range 0.575 1.25 VIN= 40 V, ON/OFF pin = 0 V

V V

SWITCH

TJ= 25°C 1.4 Over full operating temperature range 0.8 2

TJ= 25°C 0.63 Over full operating temperature range 0.53 0.73 TJ= 25°C 4.5 Over full operating temperature range 1.5 6.9

= 8 V

FEEDBACK

= 15 V

FEEDBACK

TJ= 25°C 50 100 Over full operating temperature

range

= 0 V

SWITCH

= −1 V, ON/OFF pin = 0 V 6 15 mA

SWITCH

TJ= 25°C 0.25 0.4

= 500 mA

= 1.3 V (adjustable version only) 85 nA

FEEDBACK

= 3.5 V, 50% duty cycle 400 kHz

SYNC

Over full operating temperature range

TJ= 25°C 260 Over full operating temperature

range

TJ= 25°C 20 Over full operating temperature

range

225 275

2.5 3.6

2.5

1 25 μA

7 37

150

0.6

μA

kHz

μA

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7.10 Typical Characteristics

LM2671

SNVS008L –SEPTEMBER 1998–REVISED JUNE 2016

Figure 1. Normalized Output Voltage

Figure 3. Efficiency

Figure 2. Line Regulation

Figure 4. Drain-to-Source Resistance

Figure 5. Switch Current Limit

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Figure 6. Operating Quiescent Current

LM2671

SNVS008L –SEPTEMBER 1998–REVISED JUNE 2016

Typical Characteristics (continued)

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Figure 7. Standby Quiescent Current

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

Figure 8. ON/OFF Threshold Voltage

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

LM2671

SNVS008L –SEPTEMBER 1998–REVISED JUNE 2016

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SNVS008L –SEPTEMBER 1998–REVISED JUNE 2016

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8 Detailed Description

8.1 Overview

The LM2671 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

0.5 A, and highly efficient operation. The LM2671 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. Also, see LM2670 SIMPLE SWITCHER®High Efficiency 3A Step-Down Voltage Regulator with Sync for additional applications information.

8.2 Functional Block Diagram

8.3 Feature Description

8.3.1 Switch Output

This is the output of a power MOSFET switch connected directly to the input voltage. The switch provides energy to an inductor, an output capacitor and the load circuitry under control of an internal pulse-width-modulator (PWM). The PWM controller is internally clocked by a fixed 260-kHz oscillator. In a standard step-down application the duty cycle (Time ON/Time OFF) of the power switch is proportional to the ratio of the power supply output voltage to the input voltage. The voltage on the VSWpin cycles between VIN(switch ON) and below ground by the voltage drop of the external Schottky diode (switch OFF).

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SNVS008L –SEPTEMBER 1998–REVISED JUNE 2016

Feature Description (continued)

8.3.2 Input

The input voltage for the power supply is connected to the VINpin. In addition to providing energy to the load the input voltage also provides bias for the internal circuitry of the LM2671. For ensured performance the input voltage must be in the range of 6.5 V to 40 V. For best performance of the power supply the VINpin must always be bypassed with an input capacitor placed close to this pin and GND.

8.3.3 C Boost

A capacitor must be connected from the CBpin to the VSWpin. This capacitor boosts the gate drive to the internal MOSFET above VINto fully turn it ON. This minimizes conduction losses in the power switch to maintain high efficiency. The recommended value for C Boost is 0.01 μF.

8.3.4 Ground

This is the ground reference connection for all components in the power supply. In fast-switching, high-current applications such as those implemented with the LM2671, TI recommends that a broad ground plane be used to minimize signal coupling throughout the circuit.

8.3.5 Sync

This input allows control of the switching clock frequency. If left open-circuited the regulator is switched at the internal oscillator frequency, typically 260 kHz. An external clock can be used to force the switching frequency and thereby control the output ripple frequency of the regulator. This capability provides for consistent filtering of the output ripple from system to system as well as precise frequency spectrum positioning of the ripple frequency which is often desired in communications and radio applications. This external frequency must be greater than the LM2671 internal oscillator frequency, which could be as high as 275 kHz, to prevent an erroneous reset of the internal ramp oscillator and PWM control of the power switch. The ramp oscillator is reset on the positive going edge of the sync input signal. TI recommends that the external TTL or CMOS compatible clock (between 0 V and a level greater than 3 V) be ac coupled to the SYNC pin through a 100-pF capacitor and a 1-kΩ resistor to ground.

When the SYNC function is used, current limit frequency foldback is not active. Therefore, the device may not be fully protected against extreme output short-circuit conditions.

8.3.6 Feedback

This is the input to a two-stage high gain amplifier, which drives the PWM controller. Connect the FB pin directly to the output for proper regulation. For the fixed output devices (3.3-V, 5-V and 12-V outputs), a direct wire connection to the output is all that is required as internal gain setting resistors are provided inside the LM2671. For the adjustable output version two external resistors are required to set the DC output voltage. For stable operation of the power supply it is important to prevent coupling of any inductor flux to the feedback input.

8.3.7 ON/OFF

This input provides an electrical ON/OFF control of the power supply. Connecting this pin to ground or to any voltage less than 0.8 V is completely turn OFF the regulator. The current drain from the input supply when OFF is only 50 μA. The ON/OFF input has an internal pullup current source of approximately 20 μA and a protection clamp Zener diode of 7 V to ground. When electrically driving the ON/OFF pin the high voltage level for the ON condition must not exceed the 6 V absolute maximum limit. When ON/OFF control is not required this pin must be left open.

8.4 Device Functional Modes

8.4.1 Shutdown Mode

The ON/OFF pin provides electrical ON and OFF control for the LM2671. When the voltage of this pin is lower than 1.4 V, the device enters shutdown mode. The typical standby current in this mode is 50 μA.

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Device Functional Modes (continued)

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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+ 26 hidden pages

TEXAS INSTRUMENTS LM 2671 M5,0 Instructions

Specifications and Main Features

Frequently Asked Questions

User Manual

1 Features

2 Applications

3 Description

Table of Contents

4 Revision History

5 Description (continued)

6 Pin Configuration and Functions

7 Specifications

7.1 Absolute Maximum Ratings

7.2 ESD Ratings

7.3 Recommended Operating Conditions

7.4 Thermal Information

7.5 Electrical Characteristics – 3.3 V

7.6 Electrical Characteristics – 5 V

7.7 Electrical Characteristics – 12 V

7.8 Electrical Characteristics – Adjustable

7.9 Electrical Characteristics – All Output Voltage Versions

7.10 Typical Characteristics

8 Detailed Description

8.1 Overview

8.2 Functional Block Diagram

8.3 Feature Description

8.3.1 Switch Output

8.3.2 Input

8.3.3 C Boost

8.3.4 Ground

8.3.5 Sync

8.3.6 Feedback

8.3.7 ON/OFF

8.4 Device Functional Modes

8.4.1 Shutdown Mode

8.4.2 Active Mode