LM3670MFX-ADJ National Semiconductor, LM3670MFX-ADJ Datasheet

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LM3670MFX-ADJ

Manufacturer Part Number
LM3670MFX-ADJ
Description
Miniature Step-Down DC-DC Converter for Ultra Low Voltage Circuits
Manufacturer
National Semiconductor
Datasheet

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© 2004 National Semiconductor Corporation
LM3670
Miniature Step-Down DC-DC Converter for Ultra Low
Voltage Circuits
General Description
The LM3670 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 350 mA load
current, over an input voltage range from 2.5V 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 com-
plex power management systems. Automatic intelligent
switching between PWM low-noise and PFM low-current
mode offers improved system control. During full-power op-
eration, a fixed-frequency 1 MHz (typ). PWM mode drives
loads from ∼70 mA to 350 mA max, with up to 95% efficiency.
Hysteretic PFM mode extends the battery life through reduc-
tion of the quiescent current to 15 µA (typ) during light
current loads and system standby. Internal synchronous rec-
tification provides high efficiency (90 to 95% typ. at loads
between 1 mA and 100 mA). In shutdown mode (Enable pin
pulled low) the device turns off and reduces battery con-
sumption to 0.1 µA (typ.).
The LM3670 is available in a SOT23-5 package. A high
switching frequency - 1 MHz (typ) - allows use of tiny
surface-mount components. Only three external surface-
mount components, an inductor and two ceramic capacitors,
are required.
Typical Application
FIGURE 1. 1.8V - Fixed Output Voltage - Typical Application Circuit
DS200758
Features
n V
n 2.5V ≤ V
n 15 µA typical quiescent current
n 350 mA maximum load capability
n 1 MHz PWM fixed switching frequency (typ.)
n Automatic PFM/PWM mode switching
n Available in fixed output voltages as well as an
n SOT23-5 package
n Low drop out operation - 100% duty cycle mode
n Internal synchronous rectification for high efficiency
n Internal soft start
n 0.1 µA typical shutdown current
n Operates from a single Li-Ion cell or 3 cell NiMH/NiCd
n Only three tiny surface-mount external components
n Current overload protection
Applications
n Mobile phones
n Hand-Held Radios
n Personal Digital Assistants
n Palm-top PCs
n Portable Instruments
n Battery Powered Devices
adjustable version
batteries
required (one inductor, two ceramic capacitors)
OUT
= adj (.7V min), 1.2, 1.5, 1.6, 1.8, 1.875, 2.5, 3.3V
IN
≤ 5.5V
20075801
December 2004
www.national.com

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LM3670MFX-ADJ Summary of contents

Page 1

... Only three external surface- mount components, an inductor and two ceramic capacitors, are required. Typical Application FIGURE 1. 1.8V - Fixed Output Voltage - Typical Application Circuit © 2004 National Semiconductor Corporation Features adj (.7V min), 1.2, 1.5, 1.6, 1.8, 1.875, 2.5, 3.3V OUT n 2.5V ≤ ...

Page 2

Typical Application (Continued) FIGURE 2. 1.2V - Adjustable Output Voltage - Typical Application Circuit 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 ...

Page 3

... LM3670MF-1.6 LM3670MFX-1.6 LM3670MF-1.6 LM3670MFX-1.6 1.5 LM3670MF-1.5 LM3670MFX-1.5 LM3670MF-1.5 LM3670MFX-1.5 1.2 LM3670MF-1.2 LM3670MFX-1.2 LM3670MF-1.2 LM3670MFX-1.2 Adjustable * LM3670MF-ADJ LM3670MFX-ADJ LM3670MF-ADJ LM3670MFX-ADJ *Released. Samples available. SPEC Package Marking NOPB SDEB NOPB NOPB SDDB NOPB NOPB SEFB NOPB NOPB SDCB NOPB NOPB SDBB NOPB ...

Page 4

... Absolute Maximum Ratings If Military/Aerospace specified devices are required, please contact the National Semiconductor Sales Office/ Distributors for availability and specifications. V Pin: Voltage to GND IN EN Pin: Voltage to GND FB, SW Pin: Junction Temperature (T ) J-MAX Storage Temperature Range Maximum Lead Temperature (Soldering, 10 sec.) Electrical Characteristics the full operating junction temperature range (− ...

Page 5

Electrical Characteristics the full operating junction temperature range (−40˚C ≤ =150mA, EN=V (Continued Symbol Parameter V Logic High Input IH V Logic Low Input IL I Enable (EN) Input Current EN F Internal Oscillator Frequency OSC ...

Page 6

FIGURE 4. Simplified Functional Diagram 6 20075832 ...

Page 7

Typical Performance Characteristics I vs (output pulled above regulation voltage) V vs. V OUT IN Efficiency vs. I OUT (unless otherwise stated 20075804 20075806 20075808 7 =3.6V, V =1.8V) IN OUT Shutdown vs. Temp ...

Page 8

Typical Performance Characteristics Frequency vs. Temperature Line Transient vs. Time IN OUT V = 2.6V to 3.6V IN Line Transient vs. Time IN OUT V = 3. 100 mA) ...

Page 9

Typical Performance Characteristics Load Transient vs. Time OUT LOAD I = 3mA to 280mA LOAD Load Transient vs. Time OUT LOAD I = 0mA to 280mA LOAD Load Transient vs. Time ...

Page 10

Typical Performance Characteristics PFM Mode OUT INDUCTOR Soft Start OUT INDUCTOR (I = 350mA) LOAD Operation Description DEVICE INFORMATION The LM3670, a high efficiency step down DC-DC switching ...

Page 11

Operation Description off, blocking current flow from the input, and then turns the NFET synchronous rectifier on. The inductor draws current from ground through the NFET to the output filter capacitor and load, which ramps the inductor current down with ...

Page 12

Operation Description FIGURE 5. Operation in PFM Mode and Transfer to PWM Mode Soft-Start The LM3670 will have a soft-start circuit that limits in-rush current during start-up. Typical currents and times are: Current (mA) Duration (µSec 140 280 ...

Page 13

Application Information OUTPUT VOLTAGE SELECTION FOR ADJUSTABLE LM3670 The output voltage of the adjustable parts can be pro- grammed through the resistor network connected from the to GND. V will be adjusted to make V FB OUT ...

Page 14

Application Information Model IDC2512NB100M DO1608C-103 ELL6RH100M CDRH5D18-100 OUTPUT CAPACITOR SELECTION The output filter capacitor smoothes out current flow from the inductor to the load, helps maintain a steady output voltage during transient load changes and reduces output voltage ripple. These ...

Page 15

Application Information BOARD LAYOUT CONSIDERATIONS PC board layout is an important part of DC-DC converter design. Poor board layout can disrupt the performance of a FIGURE 6. Board Layout Design Rules for the LM3670 Good layout for the LM3670 can ...

Page 16

Application Information In mobile phones, for example, a common practice is to place the DC-DC converter on one corner of the board, arrange the CMOS digital circuitry around it (since this also www.national.com generates noise), and then place sensitive preamplifiers ...

Page 17

... BANNED SUBSTANCE COMPLIANCE National Semiconductor certifies that the products and packing materials meet the provisions of the Customer Products Stewardship Specification (CSP-9-111C2) and the Banned Substances and Materials of Interest Specification (CSP-9-111S2) and contain no ‘‘Banned Substances’’ as defined in CSP-9-111S2. ...

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