ACT6305
APPLICATION INFORMATION
OUTPUT VOLTAGE SELECTION
The ACT6305 uses proprietary circuitry that
enables it to provide an one of three different
output voltage options; the ATC6305 provides
fixed output voltage options of 3.3V or 5V, or
may be adjusted over a 1.2V to 5V range by
connecting an external resistive voltage divider.
(as shown Figure 3).
FB = OUT
VOUT = 3.3V
FB = G
VOUT = 5V
FB connected to resistive
divider
VOUT = 1.18V (1+R1/R2)
Figure 3.
OUTPUT CAPACITOR SELECTION
A minimum value of capacitance is required
to maintain loop stability and normal operation of
the IC. The output capacitor value should be in
the range of 22µF to 100µF. To obtain small
output ripple, use a large capacitor with low
ESR; ceramic capacitors should be used for
highest performance. If a tantalum capacitor is
used, choose only low ESR types and a smaller
low-ESR capacitor of about 1µF can be
connected in parallel to filter high frequency
noise.
INDUCTOR SELECTION
For most applications, the inductor value
should be in the range of 10µH to 47µH. Smaller
inductors provide faster load transient response
and have a smaller physical size, but they also
result in higher ripple current and reduce the
maximum available output current. Choose
inductors with low series resistance to obtain the
highest efficiency.
BOARD LAYOUT
To reduce noise and increase efficiency, high
current traces should be wide and direct, and an
extended ground plane should be used.
Switching current paths should be laid out as
tightly as possible, with the inductor and input
and output capacitors located close to the IC, in
order to reduce electromagnetic radiation.
If the external resistor divider is used, place
the resistors very close to the FB and G pins,
and keep them away from the high switching
current paths.
Active-Semi, Inc.
- 5 -
www.active-semi.com
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