LM3674MFX-1.2 National Semiconductor, LM3674MFX-1.2 Datasheet

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LM3674MFX-1.2

Manufacturer Part Number
LM3674MFX-1.2
Description
IC,SMPS CONTROLLER,VOLTAGE-MODE,TSOP,5PIN,PLASTIC
Manufacturer
National Semiconductor
Datasheet

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© 2006 National Semiconductor Corporation
LM3674
2MHz, 600mA Step-Down DC-DC Converter in SOT 23-5
General Description
The LM3674 step-down DC-DC converter is optimized for
powering low voltage circuits from a single Li-Ion cell battery
and input voltage rails from 2.7V to 5.5V. It provides up to
600mA load current, over the entire input voltage range.
There are several fixed output voltages and adjustable out-
put voltage versions.
The device offers superior features and performance for
mobile phones and similar portable systems. During PWM
mode, the device operates at a fixed-frequency of 2 MHz
(typ). Internal synchronous rectification provides high effi-
ciency during PWM mode operation. In shutdown mode, the
device turns off and reduces battery consumption to 0.01 µA
(typ).
The LM3674 is available in SOT23-5 in leaded (PB) and
lead-free (NO PB) versions. A high switching frequency of 2
MHz (typ) allows use of only three tiny external surface-
mount components, an inductor and two ceramic capacitors.
Typical Application
DS201672
FIGURE 1. Typical Application Circuit
Features
n 600mA max load current
n Input voltage range from 2.7V to 5.5V
n Available in fixed and adjustable output voltages ranging
n Operates from a single Li-Ion cell Battery
n Internal synchronous rectification for high efficiency
n Internal soft start
n 0.01 µA typical shutdown current
n 2 MHz PWM fixed switching frequency (typ)
n SOT23-5 package
n Current overload protection and Thermal shutdown
Applications
n Mobile phones
n PDAs
n MP3 players
n Portable instruments
n W-LAN
n Digital still cameras
n Portable Hard disk drives
from 1.0V to 3.3V
protection
20167201
September 2006
www.national.com

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LM3674MFX-1.2 Summary of contents

Page 1

... PB) versions. A high switching frequency of 2 MHz (typ) allows use of only three tiny external surface- mount components, an inductor and two ceramic capacitors. Typical Application © 2006 National Semiconductor Corporation Features n 600mA max load current n Input voltage range from 2.7V to 5.5V n Available in fixed and adjustable output voltages ranging from 1 ...

Page 2

Typical Application (Continued) Connection Diagram and Package Mark Information Note: The actual physical placement of the package marking will vary from part to part. Pin Descriptions Pin # Name GND ...

Page 3

... Ordering Information Voltage Option Order Number (V) (Level 95) 1.2 LM3674MF-1.2 LM3674MFX-1.2 LM3674MF-1.2 LM3674MFX-1.2 1.5 LM3674MF-1.5 LM3674MFX-1.5 LM3674MF-1.5 LM3674MFX-1.5 1.8 LM3674MF-1.8 LM3674MFX-1.8 LM3674MF-1.8 LM3674MFX-1.8 1.875 LM3674MF-1.875 LM3674MF-1.875 LM3674MF-1.875 LM3674MF-1.875 2.8 LM3674MF-2.8 LM3674MFX-2.8 LM3674MF-2.8 LM3674MFX-2.8 ADJ LM3674MF-ADJ LM3674MFX-ADJ LM3674MF-ADJ LM3674MFX-ADJ SPEC Package Marking NO PB ...

Page 4

... Note 3: 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). National Semiconductor recommends that all intergrated circuits be handled with appropriate precautions. Failure to observe proper ESD handling techniques can result in damage ...

Page 5

Electrical Characteristics type apply over the full operating junction temperature range (−30˚C ≤ T apply to the LM3674 with 3.6V (Continued) IN Note 11: Input voltage range recommended for ideal applications performance for the specified output ...

Page 6

Block Diagram www.national.com FIGURE 4. Simplified Functional Diagram 6 20167232 ...

Page 7

Typical Performance Characteristics Quiescent Current vs. Supply Voltage (FB = 0V, No Switching) Feedback Bias Current vs. Temp Output Voltage vs. Temperature (unless otherwise stated 20167244 Output Voltage vs. Supply Voltage 20167206 Output Voltage vs. Output Current ...

Page 8

Typical Performance Characteristics 25˚C) (Continued) R vs. Temperature DSON Efficiency vs. Output Current (V = 1.5V 2.2uH, DCR = 200mΩ) OUT Efficiency vs. Output Current (V = 3.3V 2.2uH, DCR = 200mΩ) OUT www.national.com (unless otherwise ...

Page 9

Typical Performance Characteristics 25˚C) (Continued) Open/Closed Loop Current Limit vs. Temperature Load Transient Start Up (Output Current = 10mA) (unless otherwise stated: V Line Transient Response 20167297 (Output Current = 300mA) 20167247 20167224 9 = 3.6V 1.5V, T ...

Page 10

Operation Description DEVICE INFORMATION The LM3674, a high efficiency step down DC-DC switching buck converter, delivers a constant voltage from a single Li-Ion battery and input voltage rails from 2.7V to 5.5V to portable devices such as cell phones and ...

Page 11

Operation Description will be controlled down to the lowest possible input voltage. When the device operates near 100% duty cycle, the output voltage supply ripple is slightly higher, approximately 25mV. The minimum input voltage needed to support the output voltage ...

Page 12

Application Information • average to peak inductor current Ripple • maximum load current (600mA) outmax • maximum input voltage in application IN • L: min inductor value including worst case tolerances (30% drop can ...

Page 13

Application Information OUTPUT CAPACITOR SELECTION A ceramic output capacitor of 10 µF, 6.3V is sufficient for most applications. Use X7R or X5R types; do not use Y5V. DC bias characteristics of ceramic capacitors must be con- sidered when selecting case ...

Page 14

Application Information FIGURE 5. Board Layout Design Rules for the LM3674 Good layout for the LM3674 can be implemented by follow- ing a few simple design rules, as illustrated Place the LM3674, inductor and filter capacitors close ...

Page 15

... BANNED SUBSTANCE COMPLIANCE National Semiconductor follows the provisions of the Product Stewardship Guide for Customers (CSP-9-111C2) and Banned Substances and Materials of Interest Specification (CSP-9-111S2) for regulatory environmental compliance. Details may be found at: www.national.com/quality/green. ...

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