LCS700-708 datasheet(7/26 Pages) POWERINT

7 / 26 page

Rev. B 062011

LCS700-708

www.powerint.com

Figure 5.

Placement of Bypass Capacitors on Signal Pins of IC.

Figure 6.

Alternate Layout for LCS Footprint using Round Pads with Jumper Connecting

Two Grounds Highlighted.

Figure 7 shows a an example of preferred routing for the

optocoupler and traces connected to the FEEDBACK pin. The

optocoupler is spaced away from the transformer, reducing

noise pickup. The optocoupler output trace (from pin 3) is also

routed to increase the distance between it and “active”

components and traces, such as T1 and the hot side of

capacitor C12. Resistor R20 is located close to U1 rather than

optocoupler U2, so that any noise picked up on the optocoupler

trace is filtered by the combination of R20 and C4 before it gets

to the FEEDBACK pin on U1. C4 is placed directly adjacent to

the FEEDBACK pin of U1 (pin 4).

VCCH is connected to the standby supply through a high-

voltage ultrafast diode and a 2.2 W resistor connected in series.

This diode resistor network charges the VCCH bypass/storage

capacitor whenever the internal LLC low-side MOSFET is on.

The resistor limits the peak instantaneous charging current.

See R6 and D1 in Figure 8.

G Pin

LCS700-708 Datenblatt(PDF) 7 Page - Power Integrations, Inc.