AT1366B
Preliminary Product Information
1MHz,800mA Synchronous Buck Converter
VOUT × (VIN −VOUT
L× f ×VIN
)
1
IRMS
=
2 3
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 AT1366B 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:
R2
VOUT = 0.6V × (1+
)
R1
*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
1/18/2006 REV:1.2
Fax: 886-3-563-0879
WWW: http://www.aimtron.com.tw
Email:service@aimtron.com.tw
10
AIMTRON [ AIMTRON TECHNOLOGY ]
