Datasheet

LTC3422
1
3422fa
■
Wireless Handsets
■
Handheld Computers
■
GPS Receivers
■
MP3 Players
■
700mA Continuous/1A Pulsed Output Current
for Li-Ion to 5V Applications
■
Synchronous Rectification: Up to 96% Efficiency
■
True Output Disconnect
■
Inrush Current Limiting
■
Adjustable Automatic Burst Mode
®
Operation
■
Low Noise, Fixed Frequency Operation from
100kHz to 3MHz
■
0.5V to 4.5V Input Range
■
2.25V to 5.25V Adjustable Output Voltage
■
Guaranteed 1V Start-Up
■
Programmable Soft-Start
■
Synchronizable Oscillator
■
Low Quiescent Current: 25µA
■
<1µA Shutdown Current
■
Anti-Ringing Control
■
Small (3mm × 3mm × 0.75mm) Thermally Enhanced
10-Pin DFN Package
1.5A, 3MHz Synchronous
Step-Up DC/DC Converter
with Output Disconnect
2.4V to 3.3V Efficiency and Power Loss
DESCRIPTIO
U
FEATURES
APPLICATIO S
U
TYPICAL APPLICATIO
U
The LTC
®
3422 is a high efficiency, current mode, fixed
frequency, step-up DC/DC converter with true output
disconnect and inrush current limiting. The part is guaran-
teed to start up from an input voltage of 1V. The device
includes a 0.20Ω N-channel MOSFET switch and a 0.24Ω
P-channel MOSFET synchronous rectifier. The output
voltage, switching frequency, soft-start time, Burst Mode
threshold and loop compensation are all simply pro-
grammed using tiny external passive components.
Quiescent current is only 25µA during Burst Mode opera-
tion, maximizing battery life in portable applications. The
oscillator frequency can be programmed up to 3MHz and
can be synchronized to an external clock applied to the
SYNC pin.
Other features include 1µA shutdown, short-circuit protec-
tion, anti-ringing control, thermal shutdown and current
limit. The LTC3422 is available in a (3mm × 3mm × 0.75mm)
10-pin DFN package.
, LT, LTC and LTM are registered trademarks of Linear Technology Corporation.
Burst Mode is a registered trademark of Linear Technology Corporation.
All other trademarks are the property of their respective owners.
0.1µF
1nF
OFF ON
15k
22µF
4.7µF
V
IN
1.8V TO 3.2V
2 CELLS
+
2.2nF
28k
931k
V
OUT
3.3V
600mA
549k
301k
3422 TA01a
SS
V
C
BURST
SHDN FB
SYNC V
OUT
R
T
GND
V
IN
LTC3422
4.7µH
SW
22pF
LOAD CURRENT (mA)
30
EFFICIENCY (%)
POWER LOSS (mW)
90
100
20
10
80
50
70
60
40
0.1 10 100 1000
3422 TA01b
0
1000
10000
100
10
1
0
1
BURST
EFFICIENCY
PWM
EFFICIENCY
BURST
POWER
LOSSES
f
OSC
= 1MHz
PWM
POWER
LOSSES