AN82 Datasheet, PDF (2/4 Pages) Silicon Laboratories – HIGH-DENSITY MULTI CHANNEL OC-48 LAYOUT GUIDELINES FOR THE Si5100 AND Si5110

AN82
Distance
Distance is fundamentally important when observing
coupling. Adjacent Si5110s should be physically
separated by no less than 300 mil (7.6 mm). Adjacent
channels can be further separated if alternating
transceiver devices are located on opposite sides of a
PCB (see Figure 3) or if alternating devices have
shorter and longer traces to/from the associated SFP
module (see Figure 4).
Common
Metal
Heat-sink
Metal
Pedestal
125 mil
(min)
OC-48 ^SFP OC-48 ^SFP OC-48 ^SFP OC-48 ^SFP OC-48 ^SFP OC-48 ^SFP
Si5110
Si5110
Si5110
Si5110
Si5110
Si5110
Channels 1, 3, 5 topside
Channels 2, 4, 6 bottom side
Figure 3. Staggered Device Placement
(Opposite Side)
OC-48 ^SFP OC-48 ^SFP OC-48 ^SFP OC-48 ^SFP OC-48 ^SFP OC-48 ^SFP
Si5110
Si5110
Si5110
Si5110
Si5110
Si5110
Figure 4. Si5110 Staggered Device Placement
(Same Side)
Si5110
PCB
Figure 5. Common Heat-Sink Height Separation
Requirement
Summary
The Si5110 and Si5100 devices are a perfect match for
OC-48 SFP modules in both size and feature set.
However, care must be taken to minimize interference
between adjacent channels on a multi-channel card.
Considering the physical channel spacing, power supply
filtering, and heat-sinking early in the design will help
reduce costly PCB redesigns. For further technical
questions regarding the Si5110, and Si5100, please
contact a Silicon Laboratories application engineer.
Heat-Sinks
The Si5110 and Si5100 do not normally require a heat-
sink and can operate with ambient temperatures at
85 °C during their lifetime. However, if metal heat
sinking is required, the minimum spacing between
devices will need to be increased because a metal heat
sink increases the device-to-device coupling.
If metal heat sinks are attached to a common metal
shell, it is necessary to separate the heat-sinks above
the top-side of the Si5110 or Si5100 by greater than
125 mil. The 125 mil minimum-height gap can be filled
by non-metallic heat transfer materials. See Figure 5.
2
Rev. 0.1