LTC3440 Datasheet, PDF (1/20 Pages) Linear Technology – Micropower Synchronous Buck-Boost DC/DC Converter

FEATURES
■ _{Single Inductor}
■ _{Fixed Frequency Operation with Battery Voltages}
Above, Below or Equal to the Output
■ _{Synchronous Rectification: Up to 96% Efficiency}
■ _{25μA Quiescent Current in Burst Mode}^® _Operation
■ _{Up to 600mA Continuous Output Current}
■ _{No Schottky Diodes Required (VOUT < 4.3V)}
■ _{VOUT Disconnected from VIN During Shutdown}
■ _{2.5V to 5.5V Input and Output Range}
■ _{Programmable Oscillator Frequency}
from 300kHz to 2MHz
■ _{Synchronizable Oscillator}
■ _{Burst Mode Enable Control}
■ _{<1μA Shutdown Current}
■ _{Small Thermally Enhanced 10-Pin MSOP and}
(3mm
×
3mm)
DFN
U
Packages
APPLICATIO S
■ _{Palmtop Computers}
■ _{Handheld Instruments}
■ _{MP3 Players}
■ _{Digital Cameras}
LTC3440
Micropower Synchronous
Buck-Boost DC/DC Converter
DESCRIPTIO
The LTC^®3440 is a high efficiency, fixed frequency, Buck-
Boost DC/DC converter that operates from input voltages
above, below or 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 single lithium-ion, multicell alkaline or NiMH
applications where the output voltage is within the battery
voltage range.
The device includes two 0.19Ω N-channel MOSFET
switches and two 0.22Ω P-channel switches. Switching
frequencies up to 2MHz are programmed with an external
resistor and the oscillator can be synchronized to an
external clock. Quiescent current is only 25μA in Burst
Mode operation, maximizing battery life in portable appli-
cations. Burst Mode operation is user controlled and can
be enabled by driving the MODE/SYNC pin high. If the
MODE/SYNC pin has either a clock or is driven low, then
fixed frequency switching is enabled.
Other features include a 1μA shutdown, soft-start con-
trol, thermal shutdown and current limit. The LTC3440 is
available in the 10-pin thermally enhanced MSOP and
(3mm × 3mm) DFN packages.
, LT, LTC and LTM are registered trademarks of Linear Technology Corporation.
Burst Mode is a registered trademark of Linear Technology Corporation.
Protected by U.S. Patents including 6404251, 6166527.
TYPICAL APPLICATIO
Li-Ion to 3.3V at 600mA Buck-Boost Converter
L1
10μH
3
SW1
4
SW2
V_IN = 2.7V TO 4.2V
7
LTC3440
6
V_IN
V_OUT
R1
340k
+
Li-Ion
8
SHDN/SS
9
FB
C5 1.5nF
C1 *
10μF
2
10
MODE/SYNC V_C
1
R_T
5
GND
R3
15k _R2
R_T
200k
60.4k
V_OUT
3.3V
600mA
C2
22μF
*1 = Burst Mode OPERATION
0 = FIXED FREQUENCY
C1: TAIYO YUDEN JMK212BJ106MG
C2: TAIYO YUDEN JMK325BJ226MM
L1: SUMIDA CDRH6D38-100
3440 TA01
Efficiency vs V_IN
100
V_OUT = 3.3V
98 _{IOUT = 100mA}
96 ^{fOSC = 1MHz}
94
92
90
88
86
84
82
80
2.5 3.0 3.5 4.0 4.5
V_IN (V)
5.0 5.5
3440 TA02
3440fb
1