LTC3409 Datasheet, PDF (1/16 Pages) Linear Technology – 600mA Low Vin Buck Regulator in 3mm x 3mm DFN

LTC3409
600mA Low V_IN Buck
Regulator in 3mm × 3mm DFN
FEATURES
■ _{1.6V to 5.5V Input Voltage Range}
■ _{Internal Soft-Start}
■ _{Selectable 1.7MHz or 2.6MHz Constant Frequency}
Operation
■ _{Internal Oscillator can be Synchronizable to an}
External Clock, 1MHz to 3MHz Range
■ _{High Efficiency: Up to 95%}
■ _{Very Low Quiescent Current: Only 65µA During}
Burst Mode^® Operation
■ _{600mA Output Current (VIN = 1.8V, VOUT = 1.2V)}
■ _{750mA Peak Inductor Current}
■ _{No Schottky Diode Required}
■ _{Low Dropout Operation: 100% Duty Cycle}
■ _{0.613V Reference Voltage}
■ _{Stable with Ceramic Capacitors}
■ _{Shutdown Mode Draws <1µA Supply Current}
■ _{Current Mode Operation for Excellent Line and Load}
Transient Response
■ _{Overtemperature Protection}
■ _{Available in a Low Profile (0.75mm) 8-Lead}
(3mm × 3mm) DFN Package
U
APPLICATIO S
■ _{Cellular Phones}
■ _{Digital Cameras}
■ _{MP3 Players}
DESCRIPTIO
The LTC^®3409 is a high efficiency, monolithic synchro-
nous buck regulator using a constant frequency, current
mode architecture. The output voltage is adjusted via an
external resistor divider.
Fixed switching frequencies of 1.7MHz and 2.6MHz are
supported. Alternatively, an internal PLL will synchronize
to an external clock in the frequency range of 1MHz to
3MHz. This range of switching frequencies allows the use
of small surface mount inductors and capacitors, includ-
ing ceramics.
Supply current during Burst Mode operation is only 65µA
dropping to <1µA in shutdown. The 1.6V to 5.5V input
voltage range makes the LTC3409 ideally suited for single
cell Li-Ion, Li-Metal and 2-cell alkaline, NiCd or NiMH
battery-powered applications. 100% duty cycle capability
provides low dropout operation, extending battery life in
portable systems. Burst Mode operation can be user-
enabled, increasing efficiency at light loads, further ex-
tending battery life.
The internal synchronous switch increases efficiency and
eliminates the need for an external Schottky diode. Inter-
nal soft-start offers controlled output voltage rise time at
start-up without the need for external components.
, LTC and LT 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.
Protected by U.S. Patents, including 5481178, 6580258, 6304066, 6127815,
6498466, 6611131.
TYPICAL APPLICATIO
High Efficiency Step-Down Converter
V_IN
1.8V TO 5.5V
4.7µF
CER
LTC3409
V_IN
SW
RUN
MODE V_FB
SYNC GND
2.2µH*
10pF
133k ^255k
*SUMIDA CDRH2D18/LD
3409 TA01
V_OUT
1.8V
10µF
CER
Burst Mode Efficiency, 1.8V_OUT
100
1.0
90 ^2.5VIN^{, BURST}
80
70
4.2V_IN, BURST
0.1
60
3.6V_IN, BURST
50
0
40
30
POWER LOST
3.6V_IN, BURST
20
10
0
0.1
1
10
100
1000
LOAD CURRENT (mA)
3409 TA01b
3409f
1