LTC3405A_15 Datasheet, PDF (1/16 Pages) Linear Technology – 1.5MHz, 300mA Synchronous Step-Down Regulator in ThinSOT

FEATURES
■ _{High Efficiency: Up to 96%}
■ _{Very Low Quiescent Current: Only 20µA}
During Operation
■ _{300mA Output Current at VIN = 3V}
■ _{2.5V to 5.5V Input Voltage Range}
■ _{1.5MHz Constant Frequency Operation}
■ _{No Schottky Diode Required}
■ _{Low Dropout Operation: 100% Duty Cycle}
■ _{Stable with Ceramic Capacitors}
■ _{0.8V Reference Allows Low Output Voltages}
■ _{Shutdown Mode Draws < 1µA Supply Current}
■ _{±2% Output Voltage Accuracy}
■ _{Current Mode Operation for Excellent Line and}
Load Transient Response
■ _{Overtemperature Protected}
■ _{Low Profile (1mm) ThinSOT}^TM _Package
U
APPLICATIO S
■ _{Cellular Telephones}
■ _{Personal Information Appliances}
■ _{Wireless and DSL Modems}
■ _{Digital Still Cameras}
■ _{MP3 Players}
■ _{Portable Instruments}
LTC3405A
1.5MHz, 300mA
Synchronous Step-Down
Regulator in ThinSOT
DESCRIPTIO
The LTC^®3405A is a high efficiency monolithic synchro-
nous buck regulator using a constant frequency, current
mode architecture. Supply current during operation is
only 20µA and drops to <1µA in shutdown. The 2.5V to
5.5V input voltage range makes the LTC3405A ideally
suited for single Li-Ion battery-powered applications. 100%
duty cycle provides low dropout operation, extending
battery life in portable systems.
Switching frequency is internally set at 1.5MHz, allowing
the use of small surface mount inductors and capacitors.
The LTC3405A is specifically designed to work well with
ceramic output capacitors, achieving very low output
voltage ripple and a small PCB footprint.
The internal synchronous switch increases efficiency and
eliminates the need for an external Schottky diode. Low
output voltages are easily supported with the 0.8V feed-
back reference voltage. The LTC3405A is available in a low
profile (1mm) ThinSOT package.
For fixed 1.5V and 1.8V output versions, refer to the
LTC3405A-1.5/LTC3405A-1.8 data sheet.
, LTC and LT are registered trademarks of Linear Technology Corporation.
ThinSOT is a trademark of Linear Technology Corporation.
Protected by U.S. Patents, including 6580258, 5481178.
TYPICAL APPLICATIO
V_IN
2.7V
TO 5.5V
C_IN^†
2.2µF
CER
4
V_IN
3
SW
LTC3405A
1
RUN
6
5
MODE V_FB
GND
2
4.7µH**
22pF
887k
280k
3405A F01a
*V_OUT CONNECTED TO V_IN FOR 2.7V < V_IN < 3.3V
**MURATA LQH3C4R7M34
†_{TAIYO YUDEN LMK212BJ225MG}
††_{TAIYO YUDEN JMK212BJ475MG}
V_OUT*
3.3V
C_OUT^††
4.7µF
CER
Figure 1a. High Efficiency Step-Down Converter
100
95
V_IN = 3.6V
90
85
V_IN = 4.2V
80
75
V_IN = 5.5V
70
65
60
0.1
1
10
100
OUTPUT CURRENT (mA)
1000
3405A F01b
Figure 1b. Efficiency vs Load Current
3405afa
1