LTC3444_15 Datasheet, PDF (1/20 Pages) Linear Technology – Micropower Synchronous Buck-Boost DC/DC Converter for WCDMA Applications

LTC3444
Micropower Synchronous
Buck-Boost DC/DC Converter
for WCDMA Applications
FEATURES
■ _{Optimized Features for WCDMA Handsets}
■ _{Regulated Output with Input Voltages}
Above, Below, or Equal to the Output
■ _{0.5V to 5V Output Range}
■ _{Up to 400mA Continuous Output Current From}
a Single Lithium-Ion Cell
■ _{Minimal External Components}
■ _{1.5MHz Fixed Frequency Operation}
■ _{Internal Loop Compensation for Fast Response}
<25μs Full Scale Output Slewing; C_OUT 4.7μF
■ _{Output Disconnect in Shutdown}
■ _{2.75V to 5.5V Input}
■ _{<1μA Shutdown Current}
■ _{Internal Soft-Start}
■ _{Output Overvoltage Protection}
■ _{Single Inductor, No Schottky Diodes Required}
■ _{Small, Thermally Enhanced 8-Lead (3mm × 3mm)}
DFN Package
U
APPLICATIO S
■ _{WCDMA Applications–3G Handsets with High Speed}
Data Rate Capability
■ _{MP3 Players}
■ _{Digital Cameras}
DESCRIPTIO
The LTC^®3444 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 multi-cell
applications where the output voltage can vary over a wide
range.
The LTC3444 has been optimized for use in 3G WCDMA
applications. A unique design yields high efficiency at
very low output voltages while also eliminating external
components. The high speed error amplifier provides the
fast transient response required to slew the RF power
amplifier from standby to transmit and transmit to stand
by power levels. Output overvoltage protection protects
the RF power amplifier.
Operating frequency is internally set to 1.5MHz to mini-
mize external component size while maximizing efficiency.
Other features include <1μA shutdown current, internal
soft-start, peak current limit and thermal shutdown. The
LTC3444 is available in a small, thermally enhanced
8-lead (3mm × 3mm) DFN package.
, LT, LTC and LTM are registered trademarks of Linear Technology Corporation.
All other trademarks are the property of their respective owners.
Protected by U.S. Patents including 6404251, 6166527.
TYPICAL APPLICATIO
2.2μH
3.1V TO 4.2V
4.7μF
+
Li-Ion
LTC3444
SW1
SW2
V_IN
SHDN
V_OUT
FB
GND
V_C
DAC
340k
V_OUT
0.8V TO 4.2V
4.7μF
205k
267k
V_CONTROL
3444 TA01
LTC3444 Dynamic Response
V_OUT
V_CONTROL
10μs/DIV
V_IN = 3.6V, V_OUT = 0.8V TO 4.2V
V_CONTROL = 2.36V TO 0.28V, I_LOAD = 100mA
3444 G16a
3444fb
1