VSC8201DL

Rev. 1.6.3 - 9/29/04

VITESSE - CONFIDENTIAL & PROPRIETARY - DO NOT COPY WITHOUT PERMISSION

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= Ambient temperature,

= Power dissipation.

For the 128 pin LQFP vias which connect the nearby high frequency decoupling capacitors to the ground and power planes are sufficient

for the required heat dissipation rate. See “Local High-Frequency decoupling Capacitor Layout - LQFP package” on page 2.

For proper cooling of the 100 ball LBGA, a PCB via must be placed between the thermal BGA ball pads in a checkerboard pattern (see

Figure 13: ”Thermal Via Layout”, below). Each of these “thermal vias” should then be routed to the BGA ball pads near it with a wide

trace or solid copper fill to increase the conductive area on the surface of the PCB. In order to dissipate heat below the BGA package, the

PCB thermal vias must connect to a solid ground plane within the board. It is recommended that the ground plane have a minimum thick-

ness of one ounce (see Figure 14: ”Thermal Ground Plane Connections”, below).

BGA Ball Pad

PCB Thermal Via

PCB Traces

Figure 13: Thermal Via Layout

VSC8201 BGA Package

BGA Balls

1-ounce Ground Plane

Thermal via

Figure 14: Thermal Ground Plane Connections