National Semiconductor LM3671 Technical data

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LM3671 2MHz , 600mA Step-Down DC-DC Converter in SOT23-5

General Description

The LM3671 step-down DC-DC converter is optimized for powering ultra-low voltage circuits from a single Li-Ion cell or 3 cell NiMH/NiCd batteries. It provides up to 600mA load current, over an input voltage range from 2.8V to 5.5V. There are several different fixed voltage output options available as well as an adjustable output voltage version.

The device offers superior features and performance for mobile phones and similar portable applications with complex power management systems. Automatic intelligent switching between PWM low-noise and PFM low-current mode offers improved system control. During full-power operation, a fixed-frequency 2 MHz (typ). PWM mode drives loads from ∼70 mA to 600 mA max. Hysteretic PFM mode extends the battery life through reduction of the quiescent current to 16 µA (typ) at light loads and system standby. Internal synchronous rectification provides high efficiency. In shutdown mode (Enable pin pulled low) the device turns off and reduces battery consumption to 0.01 µA (typ).

The LM3671 is available in a SOT23-5 package with Pb and No Pb (Lead free) versions. A high switching frequency - 2 MHz (typ) - allows use of tiny surface-mount components. Only three external surface-mount components, an inductor and two ceramic capacitors, are required.

n 2 MHz PWM fixed switching frequency (typ) n Automatic PFM/PWM mode switching n Available in fixed output voltages and adjustable version n SOT23-5 package n Internal synchronous rectification for high efficiency n Internal soft start n 0.01 µA typical shutdown current n Operates from a single Li-Ion cell or 3 cell NiMH/NiCd

batteries

n Only three tiny surface-mount external components

required (one inductor, two ceramic capacitors)

n Current overload and Thermal shutdown protection

Applications

n Mobile phones n PDAs n MP3 players n W-LAN n Portable instruments n Digital still cameras n Portable Hard disk drives

LM3671 2MHz , 600mA Step-Down DC-DC Converter in SOT23-5

November 2004

Features

n 16 µA typical quiescent current n 600 mA maximum load capability

Typical Application Circuits

FIGURE 1. Typical Application Circuit

20108401

Typical Application Circuits (Continued)

LM3671

FIGURE 2. Typical Application Circuit for ADJ version

Connection Diagram and Package Mark Information

SOT23-5 Package

NS Package Number MF05A

20108431

20108402

Note: The actual physical placement of the package marking will vary from part to part.

FIGURE 3. Top View

Pin Description

2 GND Ground pin.

3 EN Enable pin. The device is in shutdown mode when voltage to this pin is

4 FB Feedback analog input. Connect directly to the output filter capacitor for fixed voltage

5 SW Switching node connection to the internal PFET switch and NFET synchronous

Name Description

Power supply input. Connect to the input filter capacitor (Figure 1).

enabled when

versions. For adjustable version external resistor dividers are required. The internal resistor dividers are disabled for the adjustable version.

rectifier.

1.0V. Do not leave this pin floating.

0.4V and

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Ordering Information

Voltage Option Order Number Spec Package Marking Supplied As

ADJ* LM3671MF-ADJ NOPB

LM3671MFX-ADJ NOPB 3000 units, Tape-and-Reel

LM3671MF-ADJ 1000 units, Tape-and-Reel

LM3671MFX-ADJ 3000 units, Tape-and-Reel

1.2* LM3671MF-1.2 NOPB

LM3671MFX-1.2 NOPB 3000 units, Tape-and-Reel

LM3671MF-1.2 1000 units, Tape-and-Reel

LM3671MFX-1.2 3000 units, Tape-and-Reel

1.25* LM3671MF-1.25 NOPB

LM3671MFX-1.25 NOPB 3000 units, Tape-and-Reel

LM3671MF-1.25 1000 units, Tape-and-Reel

LM3671MFX-1.25 3000 units, Tape-and-Reel

1.375 LM3671MF-1.375 NOPB

LM3671MFX-1.375 NOPB 3000 units, Tape-and-Reel

LM3671MF-1.375 1000 units, Tape-and-Reel

LM3671MFX-1.375 3000 units, Tape-and-Reel

1.5 LM3671MF-1.5 NOPB

LM3671MFX-1.5 NOPB 3000 units, Tape-and-Reel

LM3671MF-1.5 1000 units, Tape-and-Reel

LM3671MFX-1.5 3000 units, Tape-and-Reel

1.6 LM3671MF-1.6 NOPB

LM3671MFX-1.6 NOPB 3000 units, Tape-and-Reel

LM3671MF-1.6 1000 units, Tape-and-Reel

LM3671MFX-1.6 3000 units, Tape-and-Reel

1.8 LM3671MF-1.8 NOPB

LM3671MFX-1.8 NOPB 3000 units, Tape-and-Reel

LM3671MF-1.8 1000 units, Tape-and-Reel

LM3671MFX-1.8 3000 units, Tape-and-Reel

1.875 LM3671MF-1.875 NOPB

LM3671MFX-1.875 NOPB 3000 units, Tape-and-Reel

LM3671MF-1.875 1000 units, Tape-and-Reel

LM3671MFX-1.875 3000 units, Tape-and-Reel

* ADJ, 1.2 and 1.25V to be released soon.Samples available now.

SBTB

SBPB

SDRB

SEDB

SBRB

SDUB

SBSB

SDVB

1000 units, Tape-and-Reel

LM3671

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Absolute Maximum Ratings (Note 1)

If Military/Aerospace specified devices are required,

LM3671

please contact the National Semiconductor Sales Office/ Distributors for availability and specifications.

Pin: Voltage to GND −0.2V to 6.0V

FB, SW, EN Pin: (GND−0.2V) to

Continuous Power Dissipation (Note 3)

Junction Temperature (T

) +125˚C

J-MAX

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

Maximum Lead Temperature

(Soldering, 10 sec.)

ESD Rating (Note 4)

Human Body Model:

,GND,SW,FB 2.0 kV

Internally Limited

+ 0.2V)

260˚C

Human Body Model: EN 500V

Machine Model: All Pins 200V

Operating Ratings (Notes 1, 2)

Input Voltage Range 2.8V to 5.5V

Recommended Load Current 0mA to 600 mA

Junction Temperature (T

Ambient Temperature (T

) Range −25˚C to +125˚C

) Range (Note 5) −25˚C to +85˚C

Thermal Properties

Junction-to-Ambient Thermal Resistance (θ (SOT23-5) (Note 6)

)

250˚C/W

Electrical Characteristics (Notes 2, 9, 10) Limits in standard typeface are for T

type apply over the full operating junction temperature range (−25˚C ≤ T apply to the LM3671 Typical Application Circuit (Figure. 1) with V

≤ +125˚C). Unless otherwise noted, specifications

= EN = 3.6V, V

OUT

= 1.5V

= 25˚C. Limits in boldface

Symbol Parameter Condition Min Typ Max Units

OUT

REF

SHDN

Q_PFM

Input Voltage Range (Note 11) 2.8 5.5 V

Output Voltage IO=0mA −2 +4 %

= 100 mA −4 +4 %

Line Regulation 2.8V ≤ V

=10mA

Load Regulation 100 mA ≤ I

= 3.6V

≤ 5.5V

≤ 300 mA

0.045 %/V

0.0031 %/mA

Internal Reference Voltage (Note 7) 0.5 V

Shutdown Supply Current EN = 0V 0.01 1 µA

DC Bias Current into V

No load, device is not switching (FB

16 35 µA

forced higher than programmed output voltage)

DSON (P)

DSON (N)

LIM

OSC

Note 1: Absolute Maximum Ratings indicate limits beyond which damage to the component may occur. Operating Ratings are conditions under which operation of the device is guaranteed. Operating Ratings do not imply guaranteed performance limits. For guaranteed performance limits and associated test conditions, see the Electrical Characteristics tables.

Note 2: All voltages are with respect to the potential at the GND pin.

Note 3: Internal thermal shutdown circuitry protects the device from permanent damage. Thermal shutdown engages at T

130˚C (typ.).

Note 4: The Human body model is a 100 pF capacitor discharged through a 1.5 kΩ resistor into each pin. The machine model is a 200 pF capacitor discharged directly into each pin. MIL-STD-883 3015.7

Note 5: In Applications where high power dissipation and/or poor package resistance is present, the maximum ambient temperature may have to be derated. Maximum ambient temperature (T the application (P (θ

JAxPD-MAX

Note 6: Junction to ambient thermal resistance is highly application and board layout dependent. In applications where high power dissipation exists, special care must be given to thermal dissipation issues in board design. Value specified here 250 ˚C/W is based on measurement results using a 2 layer, 4" x 3", 2 oz Cu board as per JEDEC standards. The (θ

Note 7: For the ADJ version the resistor dividers should be selected such that at the desired output voltage,the voltage at the FB pin is 0.5V.

Pin-Pin Resistance for PFET VIN=VGS= 3.6V 380 500 mΩ

Pin-Pin Resistance for NFET VIN=VGS= 3.6V 250 400 mΩ

Switch Peak Current Limit Open Loop (Note 8) 830 1020 1150 mA

Logic High Input 1.0 V

Logic Low Input 0.4 V

Enable (EN) Input Current 0.01 1 µA

Internal Oscillator Frequency PWM Mode 1.6 2 2.6 MHz

= 150˚C (typ.) and disengages at TJ=

) is dependent on the maximum operating junction temperature (T

) and the junction to ambient thermal resistance of the package (θJA) in the application, as given by the following equation:T

D-MAX

). Refer to Dissipation rating table for P

A-MAX

values at different ambient temperatures.

D-MAX

) can be as low as 140 ˚C/W if a 4 layer, 4" x 3", 2/1/1/2 oz. Cu board as per JEDEC standards is used.

), the maximum power dissipation of the device in

J-MAX

A-MAX=TJ-MAX

−

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LM3671

Electrical Characteristics (Notes 2, 9, 10) Limits in standard typeface are for T

type apply over the full operating junction temperature range (−25˚C ≤ T apply to the LM3671 Typical Application Circuit (Figure. 1) with V

Note 8: Refer to datasheet curves for closed loop data and its variation with regards to supply voltage and temperature. Electrical Characteristic table reflects open loop data (FB=0V and current drawn from SW pin ramped up until cycle by cycle current limit is activated). Closed loop current limit is the peak inductor current measured in the application circuit by increasing output current until output voltage drops by 10%.

Note 9: Min and Max limits are guaranteed by design, test or statistical analysis. Typical numbers are not guaranteed, but do represent the most likely norm.

Note 10: The parameters in the electrical characteristic table are tested at V

to datasheet curves.

Note 11: Input voltage range for all voltage options is 2.8V to 5.5V. The voltage range recommended (Fixed Voltage parts) for ideal applications performance with 500mA or higher output current is given below.

= 2.8V to 4.5V for V

= 3.0V to 4.5V for V

= 1.2V, 1.25V, 1.375V, 1.5V and 1.6V.

OUT

= 1.8V and 1.875V.

OUT

= 3.6V unless otherwise specified. For performance over the input voltage range refer

≤ +125˚C). Unless otherwise noted, specifications

= EN = 3.6V, V

= 1.5V (Continued)

OUT

= 25˚C. Limits in boldface

Dissipation Rating Table

TA≤ 25˚C

Power Rating

250˚C/W 400mW 260mW 160mW

TA= 60˚C

Power Rating

TA= 85˚C

Power Rating

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