LTC3409_15 Datasheet, PDF (1/16 Pages) Linear Technology – 600mA Low VIN Buck Regulator in 3mm 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
APPLICATIONS
■ _{Cellular Phones}
■ _{Digital Cameras}
■ _{MP3 Players}
DESCRIPTION
The LTC^®3409 is a high efficiency, monolithic synchronous
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,
including 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 bat-
tery life in portable systems. Burst Mode operation can be
user-enabled, increasing efficiency at light loads, further
extending battery life.
The internal synchronous switch increases efficiency and
eliminates the need for an external Schottky diode. Internal
soft-start offers controlled output voltage rise time at start-
up without the need for external components.
, LT, LTC, LTM and Burst Mode are registered trademarks 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 APPLICATION
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
0.01
40
30
POWER LOST
3.6V_IN, BURST
0.001
20
10
0
0.0001
0.1
1
10
100
1000
LOAD CURRENT (mA)
3409 TA01b
3409fc
1