AOZ1380DI datasheet(21/24 Pages) AOSMD

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Rev. 1.3 December 2020

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AOZ1380DI

ALPHA & OMEGA

SEMIC ONDUCT OR

drop. It is also to prevent high-frequency noise on the power

line from passing through to the output. The V5V capacitor

should be located as close to the pin as possible. A 20μF

ceramic capacitor is recommended. However, higher

capacitor values further reduce the transient voltage drop

at the input.

VCHG Capacitor Selection

The VCHG capacitor for sinking path has to supply enough

current for a large load that it may encounter during system

transient. This bulk capacitor must be large enough to

supply fast transient load in order to prevent the output from

dropping.

If VCHG capacitor is too large and the output voltage is lower

than approximately 300mV of the input voltage at the end

of soft-start-time, short-circuit protection will be triggered to

turn-off the power switch.

Layout Guidelines

AOZ1380DI is a protection switch designed deliver high

current. Layout is critical to remove the heat generated by

this current. For the most efficient heat sinking, connect as

much copper as possible to the exposed pad. The exposed

pad is the common drain of the power switch which must be

electrically isolated.

On the top layer expand the exposed pad island as much as

possible for optimal thermal performance. The exposed pad

copper plane must be electrically isolated. See example in

Figure 28.

Figure 28. Top layer layout. Maximum number of VIAs

from top layer exposed pad to inner layer.

There are two ways to create thermal islands on the inner

layers. If the layer is flooded with a plane an isolated pad

may be etched out as showed in Figure 29. If there are

no flooded planes then an isolated island may be created

as showed in Figure 29. The more layers that have these

electrically isolated thermal heat sink islands the better the

thermal performance will be. Connect all isolated thermal

island (top, inner layers and bottom) together with as many

VIAs as possible.

Figure 29. Inner layer layout. Create electrically isolated

thermal island with flooded plane.

Figure 30. Inner layer layout. Create an isolated

island with no flooded plane.

On the bottom layer, similar to the inner layers, create

an isolated thermal island. Typically, there is more area

available on the bottom area for a larger thermal pad. The

top and bottom layers have better thermal performance

than the inner layers because they are exposed to the

atmosphere. See example in Figure 31.

Figure 31. Bottom layer layout. Create a large

electrically isolated thermal pad.

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