NSC LM2675-5.0MWC, LM2675-5.0MDC, LM2675-5.0EVAL Datasheet

LM2675
SIMPLE SWITCHER

®

Power Converter High Efficiency

1A Step-Down Voltage Regulator

General Description

The LM2675 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 1A load current with
excellent line and load regulation. These devices are avail­able in fixed output voltages of 3.3V, 5.0V, 12V, and an
adjustable output version.

Requiring a minimum number of external components, these
regulators are simple to use and include patented internal
frequency compensation (Patent Nos. 5,382,918 and
5,514,947) 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.

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

Other features include a guaranteed

±

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.

To simplify the LM2675 buck regulator design procedure,
there exists computer design software, LM267X Made
Simple version 6.0.

Features

n Efficiency up to 96%
n Available in SO-8, 8-pin DIP and LLP packages
n Computer Design Software LM267X Made Simple

(version 6.0)

n Simple and easy to design with
n Requires only 5 external components
n Uses readily available standard inductors
n 3.3V, 5.0V, 12V, and adjustable output versions
n Adjustable version output voltage range: 1.21V to 37V

n

±

1.5% max output voltage tolerance over line and load

conditions

n Guaranteed 1A output load current
n 0.25Ω DMOS Output Switch
n Wide input voltage range: 8V to 40V
n 260 kHz fixed frequency internal oscillator
n TTL shutdown capability, low power standby mode
n Thermal shutdown and current limit protection

Typical Applications

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

Regulator

n Efficient Pre-Regulator for Linear Regulators
n Positive-to-Negative Converter

Typical Application

01280301

SIMPLE SWITCHER®is a registered trademark of National Semiconductor Corporation.
Windows

®

is a registered trademark of Microsoft Corporation.

April 2003

LM2675 SIMPLE SWITCHER Power Converter High Efficiency 1A Step-Down Voltage Regulator

© 2003 National Semiconductor Corporation DS012803 www.national.com

Connection Diagrams

16-Lead LLP Surface Mount Package

Top View

8-Lead Package

Top View

01280338

LLP Package

See NSC Package Drawing Number LDA16A

01280302

SO-8/DIP Package

See NSC Package Drawing Number MO8A/N08E

Package Marking and Ordering Information

TABLE 1.

Output Voltage Order Information Package Marking Supplied as:

16 Lead LLP

12 LM2675LD-12 S000DB 1000 Units on Tape and Reel

12 LM2675LDX-12 S000DB 4500 Units on Tape and Reel

3.3 LM2675LD-3.3 S000EB 1000 Units on Tape and Reel

3.3 LM2675LDX-3.3 S000EB 4500 Units on Tape and Reel

5.0 LM2675LD-5.0 S000FB 1000 Units on Tape and Reel

5.0 LM2675LDX-5.0 S000FB 4500 Units on Tape and Reel

ADJ LM2675LD-ADJ S000GB 1000 Units on Tape and Reel

ADJ LM2675LDX-ADJ S000GB 4500 Units on Tape and Reel

SO-8

12 LM2675M-12 2675M-12 Shipped in Anti-Static Rails

12 LM2675MX-12 2675M-12 2500 Units on Tape and Reel

3.3 LM2675M-3.3 2675M-3.3 Shipped in Anti-Static Rails

3.3 LM2675MX-3.3 2675M-3.3 2500 Units on Tape and Reel

5.0 LM2675M-5.0 2675M-5.0 Shipped in Anti-Static Rails

5.0 LM2675MX-5.0 2675M-5.0 2500 Units on Tape and Reel

ADJ LM2675M-ADJ 2675M-ADJ Shipped in Anti-Static Rails

ADJ LM2675MX-ADJ 2675M-ADJ 2500 Units on Tape and Reel

DIP

12 LM2675N-12 LM2675N-12 Shipped in Anti-Static Rails

3.3 LM2675N-3.3 LM2675N-3.3 Shipped in Anti-Static Rails

5.0 LM2675N-5.0 LM2675N-5.0 Shipped in Anti-Static Rails

ADJ LM2675N-ADJ LM2675N-ADJ Shipped in Anti-Static Rails

LM2675

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Absolute Maximum Ratings (Note 1)

If Military/Aerospace specified devices are required, please contact the National Semiconductor Sales Office/
Distributors for availability and specifications.

Supply Voltage 45V

ON/OFF Pin Voltage

−0.1V ≤ VSH≤ 6V

Switch Voltage to Ground −1V

Boost Pin Voltage V

SW

+8V

Feedback Pin Voltage −0.3V ≤ V

FB

≤ 14V

ESD Susceptibility

Human Body Model (Note 2) 2 kV

Power Dissipation Internally Limited

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

Lead Temperature

M Package

Vapor Phase (60s) +215˚C

Infrared (15s) +220˚C

N Package (Soldering, 10s) +260˚C

LLP Package (See AN-1187)

Maximum Junction Temperature +150˚C

Operating Ratings

Supply Voltage 6.5V to 40V Junction Temperature Range −40˚C ≤ TJ≤ +125˚C

Electrical Characteristics
LM2675-3.3

Specifications with standard type face are for TJ= 25˚C, and those with bold type face apply over full

Operating Temperature Range.

Symbol Parameter Conditions Typical Min Max Units

(Note 4) (Note 5) (Note 5)

SYSTEM PARAMETERS Test Circuit Figure 2 (Note 3)

V

OUT

Output Voltage VIN= 8V to 40V, I

LOAD

= 20 mA to 1A 3.3 3.251/3.201 3.350/3.399 V

V

OUT

Output Voltage VIN= 6.5V to 40V, I

LOAD

= 20 mA to 500 mA 3.3 3.251/3.201 3.350/3.399 V

η Efficiency V

IN

= 12V, I

LOAD

=1A 86 %

LM2675-5.0

Symbol Parameter Conditions Typical Min Max Units

(Note 4) (Note 5) (Note 5)

SYSTEM PARAMETERS Test Circuit Figure 2 (Note 3)

V

OUT

Output Voltage VIN= 8V to 40V, I

LOAD

= 20 mA to 1A 5.0 4.925/4.850 5.075/5.150 V

V

OUT

Output Voltage VIN= 6.5V to 40V, I

LOAD

= 20 mA to 500 mA 5.0 4.925/4.850 5.075/5.150 V

η Efficiency V

IN

= 12V, I

LOAD

=1A 90 %

LM2675-12

Symbol Parameter Conditions Typical Min Max Units

(Note 4) (Note 5) (Note 5)

SYSTEM PARAMETERS Test Circuit Figure 2 (Note 3)

V

OUT

Output Voltage VIN= 15V to 40V, I

LOAD

= 20 mA to 1A 12 11.82/11.64 12.18/12.36 V

η Efficiency V

IN

= 24V, I

LOAD

=1A 94 %

LM2675-ADJ

Symbol Parameter Conditions Typ Min Max Units

(Note 4) (Note 5) (Note 5)

SYSTEM PARAMETERS Test Circuit Figure 3 (Note 3)

V

FB

Feedback
Voltage

VIN= 8V to 40V, I

LOAD

=20mAto1A

V

OUT

Programmed for 5V

(see Circuit of Figure 3)

1.210 1.192/1.174 1.228/1.246 V

V

FB

Feedback
Voltage

VIN= 6.5V to 40V, I

LOAD

=20mAto500mA

V

OUT

Programmed for 5V

(see Circuit of Figure 3)

1.210 1.192/1.174 1.228/1.246 V

LM2675

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LM2675-ADJ (Continued)

Symbol Parameter Conditions Typ Min Max Units

(Note 4) (Note 5) (Note 5)

η Efficiency V

IN

= 12V, I

LOAD

=1A 90 %

All Output Voltage Versions

Specifications with standard type face are for TJ= 25˚C, and those with bold type face apply over full Operating Tempera­ture Range. Unless otherwise specified, V

IN

= 12V for the 3.3V, 5V, and Adjustable versions and VIN= 24V for the 12V ver-

sion, and I

LOAD

= 100 mA.

Symbol Parameters Conditions Typ Min Max Units

DEVICE PARAMETERS

I

Q

Quiescent Current V

FEEDBACK

= 8V 2.5 3.6 mA

For 3.3V, 5.0V, and ADJ Versions

V

FEEDBACK

= 15V 2.5 mA

For 12V Versions

I

STBY

Standby Quiescent
Current

ON/OFF Pin = 0V

50 100/150 µA

I

CL

Current Limit 1.55 1.25/1.2 2.1/2.2 A

I

L

Output Leakage Current VIN= 40V, ON/OFF Pin = 0V

V

SWITCH

=0V

125µA

V

SWITCH

= −1V, ON/OFF Pin = 0V 615mA

R

DS(ON)

Switch On-Resistance I

SWITCH

= 1A 0.25 0.30/0.50 Ω

f

O

Oscillator Frequency Measured at Switch Pin 260 225 275 kHz

D Maximum Duty Cycle 95 %

Minimum Duty Cycle 0 %

I

BIAS

Feedback Bias
Current

V

FEEDBACK

= 1.3V

ADJ Version Only

85 nA

V

S/D

ON/OFF Pin
Voltage Thesholds

1.4 0.8 2.0 V

I

S/D

ON/OFF Pin Current ON/OFF Pin = 0V 20 737µA

θ

JA

Thermal Resistance N Package, Junction to Ambient (Note 6) 95 ˚C/W

M Package, Junction to Ambient (Note 6) 105

Note 1: Absolute Maximum Ratings indicate limits beyond which damage to the device may occur. Operating Ratings indicate conditions for which the device is
intended to be functional, but device parameter specifications may not be guaranteed under these conditions. For guaranteed specifications and test conditions, see
the Electrical Characteristics.

Note 2: The human body model is a 100 pF capacitor discharged through a 1.5 kΩ resistor into each pin.

Note 3: 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 Figures 2, 3 test circuits, system performance will be as specified by the system parameters section of the
Electrical Characteristics.

Note 4: Typical numbers are at 25˚C and represent the most likely norm.

Note 5: All limits guaranteed at room temperature (standard type face) and at temperature extremes (bold type face). All room temperature limits are 100%

production tested. All limits at temperature extremes are guaranteed via correlation using standard Statistical Quality Control (SQC) methods. All limits are used
to calculate Average Outgoing Quality Level (AOQL).

Note 6: Junction to ambient thermal resistance with approximately 1 square inch of printed circuit board copper surrounding the leads. Additional copper area will
lower thermal resistance further. See Application Information section in the application note accompanying this datasheet and the thermal model in LM267X Made
Simple software (version 6.0). The value θ

J−A

for the LLP (LD) 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 LLP package, refer to Application Note AN-1187.

LM2675

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Typical Performance Characteristics

Normalized

Output Voltage Line Regulation

01280303

01280304

Efficiency

Drain-to-Source

Resistance

01280305

01280306

Switch Current Limit

Operating

Quiescent Current

01280307

01280308

LM2675

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Typical Performance Characteristics (Continued)

Standby

Quiescent Current

ON/OFF Threshold

Voltage

01280309

01280310

ON/OFF Pin

Current (Sourcing) Switching Frequency

01280311 01280312

Feedback Pin

Bias Current Peak Switch Current

01280313

01280314

LM2675

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Typical Performance Characteristics (Continued)

Dropout Voltage —3.3V Option Dropout Voltage — 5.0V Option

01280315 01280316

Block Diagram

01280317

* Active Inductor Patent Number 5,514,947

†

Active Capacitor Patent Number 5,382,918

FIGURE 1.

LM2675

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Typical Performance Characteristics (Circuit of Figure 2)

Continuous Mode Switching Waveforms

V

IN

= 20V, V

OUT

= 5V, I

LOAD

=1A

L = 47 µH, C

OUT

= 68 µF, C

OUT

ESR=50mΩ

Discontinuous Mode Switching Waveforms

V

IN

= 20V, V

OUT

= 5V, I

LOAD

= 300 mA

L = 15 µH, C

OUT

= 68 µF (2x), C

OUT

ESR=25mΩ

01280318

A: VSWPin Voltage, 10 V/div.

B: Inductor Current, 0.5 A/div

C: Output Ripple Voltage, 20 mV/div AC-Coupled

Horizontal Time Base: 1 µs/div

01280319

A: VSWPin Voltage, 10 V/div.

B: Inductor Current, 0.5 A/div

C: Output Ripple Voltage, 20 mV/div AC-Coupled

Horizontal Time Base: 1 µs/div

Load Transient Response for Continuous Mode

V

IN

= 20V, V

OUT

= 5V, I

LOAD

=1A

L = 47 µH, C

OUT

= 68 µF, C

OUT

ESR=50mΩ

Load Transient Response for Discontinuous Mode

V

IN

= 20V, V

OUT

= 5V,

L = 47 µH, C

OUT

= 68 µF, C

OUT

ESR=50mΩ

01280320

A: Output Voltage, 100 mV/div, AC-Coupled.

B: Load Current: 200 mA to 1A Load Pulse

Horizontal Time Base: 50 µs/div

01280321

A: Output Voltage, 100 mV/div, AC-Coupled.

B: Load Current: 100 mA to 400 mA Load Pulse

Horizontal Time Base: 200 µs/div

LM2675

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