LM3678 DC-DC Converter Datasheet

LM3678 Datasheet, PDF, Equivalent


Part Number

LM3678

Description

High-Performance Miniature 1.5-A Step-Down DC-DC Converter

Manufacture

etcTI

Total Page 19 Pages
Datasheet
Download LM3678 Datasheet


LM3678
LM3678
www.ti.com
SNVS464C – APRIL 2008 – REVISED MAY 2013
High-Performance Miniature 1.5-A Step-Down DC-DC Converter for Handheld Applications
Check for Samples: LM3678
FEATURES
1
2 VOUT = 0.8 V or 1.2 V
• VIN = 2.5 V to 5.5 V
• 1.5-A Maximum Load Capability
• 3.3-MHz (Typical) PWM Fixed Switching
Frequency Allows Use of 1-µH Inductor
• ±3% DC Output Voltage Precision
• 0.01-µA (Typical) Shutdown Current
• Internal Synchronous Rectification for High
Efficiency
• Internal Soft Start
• Current Overload and Thermal Shutdown
Protection
APPLICATIONS
• PDAs and Smart Phones
• Personal Media Players
• W-LAN
• USB Modem Applications
• Digital Still Cameras
• Portable Hard Disk Drives
DESCRIPTION
The LM3678 step-down DC-DC converter is
optimized for powering low-voltage circuits from a
single Li-Ion cell battery and input voltage rails from
2.5 V to 5.5 V. It provides up to 1.5-A load current,
over the entire input voltage range. LM3678 offers a
0.8V or 1.2V option. One of the pair of voltages is set
through the VSELECT pin.
LM3678 operates in PWM mode with a fixed
frequency of 3.3 MHz. Internal synchronous
rectification provides high efficiency during PWM
mode operation. In shutdown mode, the device turns
off and reduces battery consumption to 0.01 µA
(typical).
The LM3678 is available in a 3mm x 3mm DSC-10
package. A high switching frequency of 3.3 MHz
(typical) allows use of tiny surface-mount
components. Only three external surface-mount
components, an inductor and two ceramic capacitors,
are required (solution size less than 33 mm2). For
voltages other than the voltage shown, contact TI or
your distributor.
VIN = 2.5V to 5.5V
CIN 10 PF
Typical Application Circuit
VDD
VDD
1 PH
SW
FB COUT
EN
PWM
LM3678
0.8V/1.2V
VSELECT
GND
PGOOD
GND
VOUT
22 PF
NOTE: VSEL H = 1.2V, VSEL L = 0.8V
Efficiency vs. Output Current
( VOUT = 1.2V)
VIN = 2.5V, 2.7V
90
80
70
60 VIN = 3.6V
50
40
30
VIN = 4.5V
20
10
0 VIN = 5.5V
Figure 1.
0.010
0.100
1.000
LOAD (A)
Figure 2.
10.000
1
Please be aware that an important notice concerning availability, standard warranty, and use in critical applications of
Texas Instruments semiconductor products and disclaimers thereto appears at the end of this data sheet.
All trademarks are the property of their respective owners.
2
PRODUCTION DATA information is current as of publication date.
Products conform to specifications per the terms of the Texas
Instruments standard warranty. Production processing does not
necessarily include testing of all parameters.
Copyright © 2008–2013, Texas Instruments Incorporated

LM3678
LM3678
SNVS464C – APRIL 2008 – REVISED MAY 2013
Functional Block Diagram
EN
VIN
www.ti.com
SW
Undervoltage
Lockout
Ramp
Generator
Soft
Start
Thermal
Shutdown
Bandgap
2 MHz
Oscillator
Current Limit
Comparator
+
- Ref1
PFM Current
Comparator
+
- Ref2
Error
Amp
PWM Comparator
Control Logic
Driver
VREF +
0.5V -
VCOMP +
1.0V -
Frequency
Compensation
+
-
Zero Crossing
Comparator
Fixed Ver
FB VSELECT
PGOOD PWM
Figure 3. LM3678 Block Diagram
GND
2 Submit Documentation Feedback
Product Folder Links: LM3678
Copyright © 2008–2013, Texas Instruments Incorporated


Features LM3678 www.ti.com SNVS464C – APRIL 2 008 – REVISED MAY 2013 High-Performa nce Miniature 1.5-A Step-Down DC-DC Con verter for Handheld Applications Check for Samples: LM3678 FEATURES 1 •2 VO UT = 0.8 V or 1.2 V • VIN = 2.5 V to 5.5 V • 1.5-A Maximum Load Capability • 3.3-MHz (Typical) PWM Fixed Switch ing Frequency Allows Use of 1-µH Induc tor • ±3% DC Output Voltage Precisio n • 0.01-µA (Typical) Shutdown Curre nt • Internal Synchronous Rectificati on for High Efficiency • Internal Sof t Start • Current Overload and Therma l Shutdown Protection APPLICATIONS • PDAs and Smart Phones • Personal Medi a Players • W-LAN • USB Modem Appli cations • Digital Still Cameras • P ortable Hard Disk Drives DESCRIPTION T he LM3678 step-down DC-DC converter is optimized for powering low-voltage circ uits from a single Li-Ion cell battery and input voltage rails from 2.5 V to 5 .5 V. It provides up to 1.5-A load curr ent, over the entire input voltage range. LM3678 offers a 0.8V or 1.2V option. One of the pair of vo.
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