Rev. C 03/14

10

LinkSwitch-HP

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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.

Another consideration for ESD and line surge is the primary-

side termination of the Y capacitor. The Y capacitor C18 should

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.

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.

Figure 12. Layout for 30 W Adapter Using a eSIP-7C Package (View From Bottom Copper Layer).