AT1361
1MHz,1A Synchronous Buck Converter
When choosing the input and output ceramic capacitors, choose the X5R or X7R dielectric
formulations. These dielectrics have the best temperature and voltage characteristics of all
the ceramics for a given value and size.
Inductor Selection
The inductor is chosen based on the desired ripple current. Large value inductors lower
ripple current and small value inductors result in higher ripple current. Always consider the
losses associated with the DCR and its effect on the total converter efficiency when
selecting an inductor. The inductor is selected to limit the ripple current to some
predetermined value, typically 20~40% of the full load current at the maximum input
voltage. The formula of inductance value is as below:
∆IL = 0.2 ~ 0.4× IOUT (MAX )
⎛
⎞
VOUT
VOUT
VIN
⎜
⎜
⎟
⎟
L =
1−
f × ∆IL
⎝
⎠
Adjustable Output Voltage
The AT1361 appears a 0.6V reference voltage at FB pin. The output voltage is set by a
resistive divider which is according to the following formula:
0.6V=VOUT=5.5V
R2
FB
R2
VOUT = 0.6V × (1+
)
R1
R1
GND
*R1=150KΩ for stability consideration.
7F, No.9, PARK AVENUE II, Science-Based Industrial Park, Hsinchu 300,Taiwan, R.O.C.
Tel: 886-3-563-0878
1/11/2008 REV:1.0
Fax: 886-3-563-0879
WWW: http://www.aimtron.com.tw
Email:service@aimtron.com.tw
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AIMTRON [ AIMTRON TECHNOLOGY ]
