LTC3440_15 Datasheet, PDF (1/20 Pages) Linear Technology – Micropower Synchronous Buck-Boost DC/DC Converter

LTC3440
Micropower Synchronous
Buck-Boost DC/DC Converter
Features
n _{Single Inductor}
n _{Fixed Frequency Operation with Battery Voltages}
Above, Below or Equal to the Output
n _{Synchronous Rectification: Up to 96% Efficiency}
n _{25µA Quiescent Current in Burst Mode}^® _Operation
n _{Up to 600mA Continuous Output Current}
n _{No Schottky Diodes Required (VOUT < 4.3V)}
n _{VOUT Disconnected from VIN During Shutdown}
n _{2.5V to 5.5V Input and Output Range}
n _{Programmable Oscillator Frequency}
from 300kHz to 2MHz
n _{Synchronizable Oscillator}
n _{Burst Mode Enable Control}
n _{<1µA Shutdown Current}
n _{Small Thermally Enhanced 10-Pin MSOP and}
(3mm × 3mm) DFN Packages
Applications
n _{Palmtop Computers}
n _{Handheld Instruments}
n _{MP3 Players}
n _{Digital Cameras}
Description
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 prod-
uct 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. Switch-
ing 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
applications. 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.
L, LT, LTC, LTM, Linear Technology, Burst Mode and the Linear logo are registered
trademarks and ThinSOT is a trademark of Linear Technology Corporation. All other
trademarks are the property of their respective owners.
TYPICAL Application
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
2
10
C1 *
MODE/SYNC V_C
10µF ₁
R_T
5
GND
R_T
R3
15k _R2
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
98
V_OUT = 3.3V
I_OUT = 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
For more information www.linear.com/LTC3440
3440fc
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