National Semiconductor LM2675 Technical data

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 ( per 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 output voltage within specified input voltages and output load conditions, and ternal 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.

10% on the oscillator frequency. Ex-

90%), the cop-

1.5% tolerance on

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

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

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

June 2005

Typical Application

01280301

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

Windows

is a registered trademark of Microsoft Corporation.

Connection Diagrams

LM2675

16-Lead LLP Surface Mount Package

Top View

8-Lead Package

Top View

SO-8/DIP Package

See NSC Package Drawing Number MO8A/N08E

01280338

LLP Package

See NSC Package Drawing Number LDA16A

01280302

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

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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.

LM2675

Supply Voltage 45V

ON/OFF Pin Voltage

−0.1V ≤ VSH≤ 6V

Switch Voltage to Ground −1V

Boost Pin Voltage V

Feedback Pin Voltage −0.3V ≤ V

+8V

≤ 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

Operating Temperature Range.

Symbol Parameter Conditions Typical Min Max Units

SYSTEM PARAMETERS Test Circuit Figure 2 (Note 3)

OUT

η Efficiency V

Output Voltage VIN= 8V to 40V, I

Output Voltage VIN= 6.5V to 40V, I

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

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

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

LOAD

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

LOAD

= 12V, I

=1A 86 %

LOAD

LM2675-5.0

Symbol Parameter Conditions Typical Min Max Units

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

SYSTEM PARAMETERS Test Circuit Figure 2 (Note 3)

OUT

η Efficiency V

Output Voltage VIN= 8V to 40V, I

Output Voltage VIN= 6.5V to 40V, I

= 12V, I

=1A 90 %

LOAD

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

LOAD

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

LOAD

LM2675-12

Symbol Parameter Conditions Typical Min Max Units

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

SYSTEM PARAMETERS Test Circuit Figure 2 (Note 3)

OUT

η Efficiency V

Output Voltage VIN= 15V to 40V, I

= 24V, I

LOAD

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

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)

Feedback Voltage

VIN= 8V to 40V, I

Programmed for 5V

OUT

LOAD

(see Circuit of Figure 3)

VIN= 6.5V to 40V, I

Programmed for 5V

OUT

LOAD

(see Circuit of Figure 3)

=20mAto1A

1.210 1.192/1.174 1.228/1.246 V

=20mAto500mA

1.210 1.192/1.174 1.228/1.246 V

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LM2675-ADJ (Continued)

LM2675

Symbol Parameter Conditions Typ Min Max Units

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

η Efficiency V

= 12V, I

=1A 90 %

LOAD

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

sion, and I

LOAD

= 100 mA.

Symbol Parameters Conditions Typ Min Max Units

DEVICE PARAMETERS

STBY

Quiescent Current V

Standby Quiescent Current

DS(ON)

Current Limit 1.55 1.25/1.2 2.1/2.2 A

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

Switch On-Resistance I

Oscillator Frequency Measured at Switch Pin 260 225 275 kHz

D Maximum Duty Cycle 95 %

Minimum Duty Cycle 0 %

BIAS

Feedback Bias Current

S/D

ON/OFF Pin Voltage Thesholds

S/D

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 thermal vias. For improved thermal resistance and power dissipation for the LLP package, refer to Application Note AN-1187.

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

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

for the LLP (LD) package is specifically dependent on PCB trace area, trace material, and the number of layers and

J−A

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

FEEDBACK

= 8V 2.5 3.6 mA

For 3.3V, 5.0V, and ADJ Versions

FEEDBACK

= 15V 2.5 mA

For 12V Versions

ON/OFF Pin = 0V

SWITCH

=0V

SWITCH

= −1V, ON/OFF Pin = 0V 615mA

SWITCH

= 1A 0.25 0.30/0.50 Ω

FEEDBACK

= 1.3V

ADJ Version Only

50 100/150 µA

125µA

85 nA

1.4 0.8 2.0 V

M Package, Junction to Ambient (Note 6) 105

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Typical Performance Characteristics

Normalized

Output Voltage Line Regulation

LM2675

Efficiency

Switch Current Limit

01280303

01280305

01280304

Drain-to-Source

Resistance

01280306

Operating

Quiescent Current

01280307

01280308

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Typical Performance Characteristics (Continued)

LM2675

Standby

Quiescent Current

01280309

ON/OFF Threshold

Voltage

ON/OFF Pin

Current (Sourcing) Switching Frequency

01280310

01280311 01280312

Feedback Pin

Bias Current Peak Switch Current

01280313

01280314

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Typical Performance Characteristics (Continued)

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

01280315 01280316

Block Diagram

LM2675

* Active Inductor Patent Number 5,514,947

†

Active Capacitor Patent Number 5,382,918

01280317

FIGURE 1.

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Typical Performance Characteristics (Circuit of Figure 2)

LM2675

Continuous Mode Switching Waveforms

= 20V, V

L = 47 µH, C

OUT

= 5V, I

OUT

= 68 µF, C

=1A

LOAD

ESR=50mΩ

OUT

Discontinuous Mode Switching Waveforms

= 20V, V

L = 15 µH, C

OUT

= 5V, I

OUT

LOAD

= 68 µF (2x), C

= 300 mA

ESR=25mΩ

OUT

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

= 20V, V

L = 47 µH, C

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

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

OUT

= 5V, I

OUT

= 68 µF, C

=1A

LOAD

ESR=50mΩ

OUT

Horizontal Time Base: 50 µs/div

01280318

01280320

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 Discontinuous Mode

= 20V, V

L = 47 µH, C

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

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

OUT

= 68 µF, C

OUT

= 5V,

OUT

ESR=50mΩ

Horizontal Time Base: 200 µs/div

01280319

01280321

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