FEATURES
■ High Efficiency: Up to 96%
■ 600mA 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
■ Low Quiescent Current: 300µA
■ 0.6V Reference Allows Low Output Voltages
■ Shutdown Mode Draws < 1µA Supply Current
■ Current Mode Operation for Excellent Line and
Load Transient Response
■ Overtemperature Protected
■ Low Profile (1mm) ThinSOTTM Package
U
APPLICATIO S
■ Cellular Telephones
■ Personal Information Appliances
■ Wireless and DSL Modems
■ Digital Still Cameras
■ MP3 Players
■ Portable Instruments
LTC3406B
1.5MHz, 600mA
Synchronous Step-Down
Regulator in ThinSOT
DESCRIPTIO
The LTC®3406B is a high efficiency monolithic synchro-
nous buck regulator using a constant frequency, current
mode architecture. The device is available in an adjustable
version and fixed output voltages of 1.5V and 1.8V. Supply
current with no load is 300µA and drops to <1µA in
shutdown. The 2.5V to 5.5V input voltage range makes the
LTC3406B ideally suited for single Li-Ion battery-powered
applications. 100% duty cycle provides low dropout op-
eration, extending battery life in portable systems. PWM
pulse skipping mode operation provides very low output
ripple voltage for noise sensitive applications.
Switching frequency is internally set at 1.5MHz, allowing
the use of small surface mount inductors and capacitors.
The internal synchronous switch increases efficiency and
eliminates the need for an external Schottky diode. Low
output voltages are easily supported with the 0.6V feed-
back reference voltage. The LTC3406B is available in a low
profile (1mm) ThinSOT package. Refer to LTC3406 for
applications that require Burst Mode® operation.
, LTC and LT are registered trademarks of Linear Technology Corporation.
Burst Mode is a registered trademark of Linear Technology Corporation.
ThinSOT is a trademark of Linear Technology Corporation.
Protected by U.S. Patents, including 6580258, 5481178.
TYPICAL APPLICATIO
VIN
2.7V
TO 5.5V
CIN**
4.7µF
CER
4
VIN
3 2.2µH*
SW
LTC3406B-1.8
1
5
RUN VOUT
GND
2
COUT†
10µF
CER
VOUT
1.8V
600mA
3406B F01a
*MURATA LQH32CN2R2M33
**TAIYO YUDEN JMK212BJ475MG
†TAIYO YUDEN JMK316BJ106ML
Figure 1a. High Efficiency Step-Down Converter
100
VOUT = 1.8V
90
80
70
VIN = 3.6V
60
50
VIN = 2.7V
40
30
20
VIN = 4.2V
10
0.1
1
10
100
OUTPUT CURRENT (mA)
1000
3406B F01b
Figure 1b. Efficiency vs Load Current
3406bfa
1