LTC3409A_15 Datasheet, PDF (1/16 Pages) Linear Technology – 600mA Low VIN Buck Regulator in 3mm 3mm DFN

LTC3409A
600mA Low V_IN Buck
Regulator in 3mm × 3mm DFN
FEATURES
n _{1.6V to 5.5V Input Voltage Range}
n _{0.62V to 5.5V Output Voltage Range}
n _{Internal Soft-Start}
n _{Selectable 1.7MHz or 2.6MHz Constant Frequency}
Operation
n _{Internal Oscillator Can Be Synchronized to an}
External Clock, 1MHz to 3MHz Range
n _{High Efficiency: Up to 95%}
n _{65μA Quiescent Current, Burst Mode}^® _Operation
n _{600mA Output Current (VIN = 1.8V, VOUT = 1.2V)}
n _{750mA Peak Inductor Current}
n _{No Schottky Diode Required}
n _{Low Dropout Operation: 100% Duty Cycle}
n _{0.612V Reference Voltage}
n _{Stable with Ceramic Capacitors}
n _{Shutdown Mode Draws <1μA Supply Current}
n _{Current Mode Operation for Excellent Line and Load}
Transient Response
n _{Overtemperature Protection}
n _{Available in a Low Profile (0.75mm)}
8-Lead (3mm × 3mm) DFN Package
APPLICATIONS
n _{Cellular Phones}
n _{Digital Cameras}
n _{MP3 Players}
DESCRIPTION
The LTC^®3409A is a high efficiency, monolithic synchronous
buck regulator using a constant frequency, current mode
architecture. The LTC3409A improves upon the LTC3409’s
light load regulation in Burst Mode operation. 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 LTC3409A 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.
L, LT, LTC, LTM, Linear Technology and the Linear logo 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
LTC3409A
V_IN
SW
RUN
MODE V_FB
SYNC GND
2.2μH*
10pF
267k
137k
*SUMIDA CDRH2D18/LD
V_OUT
1.8V
22μF
s2
3409A TA01
Burst Mode Efficiency, 1.8V_OUT
100
1
90 ^2.5VIN^{, BURST}
80
0.1
70
60
3.6V_IN, BURST
50
0.01
40
4.2V_IN, BURST
POWER LOST
30
3.6V_IN, BURST
0.001
20
10
0
0.0001
0
1
10
100
1000
LOAD CURRENT (mA)
3409A TA01b
3409af
1