LNK562-564
TOP VIEW
LinkSwitch-LP
D
Y1-
Capacitor
FB
BP
S
S
C
BP
Input Filter
Capacitor
S
S
Tr a n s f o r m e r
-
+
DC
OUT
HV DC
+
INPUT
-
Output Filter
Capacitor
Maximize hatched copper
areas (
) for optimum
heatsinking
PI-4157-101305
Figure 6. Recommended Circuit Board Layout for LinkSwitch-LP using P Package (Assumes a HVDC Input Stage).
LinkSwitch-LP
Layout Considerations
Layout
See Figure 6 for a recommended circuit board layout for
LinkSwitch-LP
(P & G package).
Single Point Grounding
Use a single point ground connection from the input
fi
lter
capacitor to the area of copper connected to the SOURCE pins.
Bypass Capacitor (C
BP
)
The BYPASS pin capacitor should be located as near as possible
to the BYPASS and SOURCE pins.
Primary Loop Area
The area of the primary loop that connects the input
fi
lter
capacitor, transformer primary and
LinkSwitch-LP
together
should be kept as small as possible.
Primary Clamp Circuit
An external clamp may be used to limit peak voltage on the
DRAIN pin at turn off. This can be achieved by using an RCD
clamp or a Zener (~200 V) and diode clamp across the primary
winding. In all cases, to minimize EMI, care should be taken
to minimize the circuit path from the clamp components to the
transformer and
LinkSwitch-LP.
Thermal Considerations
The copper area underneath the
LinkSwitch-LP
acts not only as
a single point ground, but also as a heatsink. As it is connected
to the quiet source node, this area should be maximized for
good heat sinking of
LinkSwitch-LP.
The same applies to the
cathode of the output diode.
Y-Capacitor
The placement of the Y-type cap should be directly from the
primary input
fi
lter capacitor positive terminal to the common/
return terminal of the transformer secondary. Such a placement
will route high magnitude common-mode surge currents away
from the
LinkSwitch-LP
device. Note: If an input pi (C, L, C)
EMI
fi
lter is used, then the inductor in the
fi
lter should be placed
between the negative terminals on the input
fi
lter capacitors.
6
Rev. H 11/08
POWERINT [ POWER INTEGRATIONS, INC. ]
