KB3408 Datasheet, PDF (1/6 Pages) Kingbor Technology Co – 1.5MHz,350mA Synchronous Step-Down Regulator in SOT23-5

Kingbor Technology Co.,Ltd
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KB3408
1.5MHz, 350mA
Synchronous Step-Down
Regulator in _SOT23-5
FEATURES
■ _{High Efficiency: Up to 96%}
■ _{Very Low Quiescent Current: Only 20µA}
During Operation
■ _{350mA Output Current}
■ _{2.5V to 7.4V Input Voltage Range}
■ _{1.5MHz Constant Frequency Operation}
■ _{No Schottky Diode Required}
■ _{Low Dropout Operation: 100% Duty Cycle}
■ _{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) SOT23-5 Package}
APPLICATIONS
■ _{Cellular Telephones}
■ _{Personal Information Appliances}
■ _{Wireless and DSL Modems}
■ _{Digital Still Cameras}
■ _{MP3 Players}
■ _{Portable Instruments}
DESCRIPTION
The KB3408 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 1.8V and 3.3V. Supply
current during operation is only 20µA and drops to )1µA
in shutdown. The 2.5V to 7.4V input voltage range makes
the KB3408 ideally suited for single Li-Ion battery-pow-
ered applications. 100% duty cycle provides low dropout
operation, extending battery life in portable systems.
Automatic Burst Mode operation increases efficiency at
light loads, further extending battery life.
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 KB3408 is available in a low
profile (1mm) SOT23-5 package.
TYPICAL APPLICATION
V_IN
2.7V
TO 7.4V
+ ^CIN
4.7µF
Tan
4
V_IN
4.7µH
3
SW
KB3408-1.8
1
5
RUN V_OUT
GND
2
C_OUT
10µF
CER
V_OUT
1.8V
350mA
Figure 1a. High Efficiency Step-Down Converter
95
V_IN = 2.7V
90
85
V_IN = 3.6V
80
V_IN = 4.2V
75
70
65
60
0.1
V_OUT = 1.8V
1
10
100
500
OUTPUT CURRENT (mA)
Figure 1b. Efficiency vs Load Current
March 2007
1
KB3408