LTC3563_15 Datasheet, PDF (1/16 Pages) Linear Technology – 500mA, Synchronous Step-Down DC/DC Converter with Selectable Output Voltage

LTC3563
500mA, Synchronous
Step-Down DC/DC Converter
with Selectable Output Voltage
FEATURES
DESCRIPTIO
■ _{High Efficiency: Up to 96%}
■ _{Pin Selectable Output Voltage: 1.28V/1.87V}
■ _{Low Ripple (<20mVP-P) Burst Mode}^® _Operation:
I_Q = 26µA
■ _{Very Low Quiescent Current: Only 26µA}
■ _{2.5V to 5.5V Input Voltage Range}
■ _{2.25MHz Constant Frequency Operation}
■ _{Low Dropout Operation: 100% Duty Cycle}
■ _{No Schottky Diode Required}
■ _{Internal Soft-Start Limits Inrush Current}
■ _{Shutdown Mode Draws <1µA Supply Current}
■ _{±2% Output Voltage Accuracy}
■ _{Current Mode Operation for Excellent Line and Load}
Transient Response
■ _{Overtemperature Protected}
■ _{Available in 2mm × 2mm 6-Lead DFN}
U
APPLICATIO S
■ _{Cellular Telephones}
■ _{Wireless and DSL Modems}
■ _{Digital Cameras}
■ _{MP3 Players}
■ _{PDAs and Other Handheld Devices}
The LTC^®3563 is a high efficiency monolithic synchro-
nous buck converter using a constant frequency, current
mode architecture. A voltage select input allows the user
to program the output voltage to 1.28V or 1.87V. Supply
current during operation is only 26µA, dropping to <1µA in
shutdown. The 2.5V to 5.5V input voltage range makes the
LTC3563 ideally suited for single Li-Ion battery-powered
applications. 100% duty cycle provides low dropout opera-
tion, extending battery life in portable systems. Internal
power switches are optimized to provide high efficiency
and eliminate the need for an external Schottky diode.
The switching frequency is internally set at 2.25MHz,
allowing the use of small surface mount inductors and
capacitors. The LTC3563 is specifically designed to work
well with ceramic output capacitors, achieving very low
output voltage ripple and a small PCB footprint.
The LTC3563 is configured for the power saving Burst
Mode Operation.
, LTC, LT, 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, 5994885.
TYPICAL APPLICATIO
V_IN
2.7V TO 5.5V
C_IN
10µF
CER
1.28V 1.87V
V_IN
SW
LTC3563
RUN V_OUT
V_SEL
GND
2.2µH
V_OUT
1.28V/1.87V
500mA
C_OUT
10µF
CER
3563 TA01a
Efficiency and Power Loss vs Output Current
100
90
80
70
60
50
40
30
20
10
0
0.1
1000
100
10
1
V_IN = 3.6V
V_OUT = 1.87V
0.1
1
10
100
1000
OUTPUT CURRENT (mA)
3563 TA01b
3563f
1