LinkSwitch-HP
be tied to the positive terminal of the bulk capacitor C2 in order
to route the potential of high currents away from the more
sensitive primary return traces.
Layout Considerations for eSIP-7C Package
Figure 12 is the layout for a 30 W adapter shown in the schematic
Figure 11. An eSIP-7C package is used as indicated by the
suffix in LNK6766E which allows the use of a stand-up heat
sink. The mounting pin for the heat sink should be electrically
isolated. It can be seen that the primary return trace wraps
around the LinkSwitch-HP device which acts as a shield around
the critical external control related components of LinkSwitch-HP.
These components include R7, R8, R19, R20 and C5, C8, C20.
Of particular importance is placing the bypass capacitor C5 and
COMPENSATION pin noise filter capacitor C8 as close as possible
to SOURCE pin with very short trace lengths to COMPENSATION
and BYPASS pins as shown. If an electrolytic capacitor is
selected as the bypass capacitor (C5) then an additional 100 nF
(C5) ceramic must also be fitted. The ground trace wrap, tight
layout and single point grounding to SOURCE pin of these
components avoids having noise related issues during peak
loads or during line transient such as surge or ESD events.
Because of the tight layout common to adapter applications,
this design uses triple insulated wire and flying leads for output
winding termination to avoid secondary arcing to core during
ESD events.
The trace connecting the drain to transformer should be very
short and the primary clamp circuitry should be grouped
together and away from the more sensitive components. The
bias winding return and return of bias capacitor C6 should be
routed separately to the negative terminal of the input capacitor
C2 away from SOURCE pin.
The secondary rectifying loop that includes the secondary
winding, the output diode D8, and the first output capacitor C13
should be as tight as possible to minimize adding series
inductance which can reduce high load efficiency and degrade
the quality of regulation.
Another consideration for ESD and line surge is the primary-
side termination of the Y capacitor. The Y capacitor C18 should
Figure 12. Layout for 30 W Adapter Using a eSIP-7C Package (View From Bottom Copper Layer).
10
Rev. C 03/14
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