aoz1341 Alpha & Omega Semiconductor, aoz1341 Datasheet - Page 10

• Manufacturer Part Number: aoz1341
• Description: Dual Channel Usb Switch
• Manufacturer: Alpha & Omega Semiconductor

Applications Information
Input Capacitor Selection
The input capacitor prevents large voltage transients
from appearing at the input, and provides the
instantaneous current needed each time the switch turns
on and also to limit input voltage drop. The input
capacitor t also prevents high-frequency noise on the
power line from passing through the output of the power
side. The choice of the input capacitor is based on its
ripple current and voltage ratings rather than its capacitor
value. The input capacitor should be located as close to
the VIN pin as possible. A 0.1 μF ceramic cap is
recommended but higher capacitor values will further
reduce the voltage drop at the input.
Output Capacitor Selection
The output capacitor acts in a similar way. A small 0.1 μF
capacitor prevents high-frequency noise from going into
the system. Also, the output capacitor has to supply
enough current for a large load that it may encounter
during system transients. This bulk capacitor must be
large enough to supply fast transient load in order to
prevent the output voltage from dropping.
Rev. 1.0 April 2011
www.aosmd.com
Power Dissipation Calculation
Calculate the power dissipation for normal load condition
using the following equation:
P
The worst case power dissipation occurs when the load
current hits the current limit due to over-current or short
circuit faults. The power dissipation under these
conditions can be calculated using the following
equation:
P
Layout Guidelines
Proper PCB layout is important for improving the thermal
and overall performance of the AOZ1341. To optimize the
switch response time to output short-circuit conditions
keep all traces as short as possible to reduce the effect of
unwanted parasitic inductance.
Place the input and output bypass capacitors as close as
possible to the IN and OUT pins. The input and output
PCB traces should be as wide as possible for the given
PCB space.
Use a ground plane to enhance the power dissipation
capability of the device.
D
D
= R
= (V
ON
IN
– V
x (I
OUT
OUT
)
) x I
2
LIMIT
AOZ1341
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