LTC3442
1
3442f
, LTC and LT are registered trademarks of Linear Technology Corporation. All other
trademarks are the property of their respective owners. Burst Mode is a registered
trademark of Linear Technology Corporation. Protected by U.S. Patents including 6404251,
6166527.
SW1
V
IN
SHDN/SS
R
LIM
R
T
SGND
SW2
V
OUT
FB
V
C
BURST
PGND
LTC3442
10µF
0.01µF
V
IN
2.5V TO
4.2V
Li-Ion
340k 2.2k
22µF
220pF
V
OUT
3.3V
1.2A
200k
0.01µF
15k
470pF
3442 TA01a
4.7µH
1M
71.5k 200k
TYPICAL APPLICATIO
U
APPLICATIO S
U
FEATURES
DESCRIPTIO
U
Micropower Synchronous
Buck-Boost DC/DC Converter with
Automatic Burst Mode Operation
The LTC
®
3442 is a highly efficient, fixed frequency, Buck-
Boost DC/DC converter, which operates from input volt-
ages above, below, and equal to the output voltage. The
topology incorporated in the IC provides a continuous
transfer function through all operating modes, making the
product ideal for a single Lithium-Ion or multicell alkaline
applications where the output voltage is within the battery
voltage range.
The device includes two 0.10Ω N-channel MOSFET
switches and two 0.10Ω P-channel switches. Operating
frequency and average input current limit can each be
programmed with an external resistor. Quiescent current
is only 35µA in Burst Mode operation, maximizing battery
life in portable applications. Automatic Burst Mode opera-
tion allows the user to program the load current for Burst
Mode operation, or to control it manually.
Other features include 1µA shutdown current, program-
mable soft-start, peak current limit and thermal shutdown.
The LTC3442 is available in a low profile, thermally en-
hanced 12-lead (4mm × 3mm × 0.75mm) DFN package.
■
PDA/‘SMART’ Phones
■
Handheld Computers
■
MP3 Players
■
Handheld Instruments
■
Digital Cameras
■
Wireless Handsets
■
USB Peripherals
Efficiency vs V
IN
V
IN
(V)
2.5
EFFICIENCY (%)
100
90
80
70
60
50
3.0 3.5 4.0 4.5
3442 • TA01b
5.0 5.5
1A LOAD
300mA LOAD
V
OUT
= 3.3V
L = 4.7µH
F = 600kHz
■
Regulated Output with Input Voltages Above,
Below, or Equal to the Output
■
Single Inductor, No Schottky Diodes Required
■
Manual or Programmable Automatic Burst Mode
®
Operation
■
Programmable Average Input Current Limit
■
Up to 1.2A Continuous Output Current from a Single
Lithium-Ion Cell
■
High Efficiency: Up to 95%
■
Output Disconnect in Shutdown
■
2.4V to 5.5V Input Range
■
2.4V to 5.25V Output Range
■
35µA Quiescent Current in Burst Mode Operation
■
Programmable Frequency from 300kHz to 2MHz
■
<1µA Shutdown Current
■
Small, Thermally Enhanced 12-Lead (4mm × 3mm)
DFN Package