SL876Q5-A
Product User Guide
1VV0301333 Rev. 2
Page 50 of 68
2017-06-27
PCB stack and Trace Impedance
It is important to maintain a 50
Ω
impedance on the RF path trace. Design software for
calculating trace impedance can be found from multiple sources on the internet. The best
method is to contact your PCB supplier and request a stackup for a 50
Ω
controlled impedance
board. They will give you a suggested trace width along with PCB stackup needed to create
the 50
Ω
impedance.
It is also important to consider the effects of component pads that are in the path of the 50
Ω
trace. If the traces are shorter than a 1/16th wavelength, transmission line effects will be
minimized, but stray capacitance from large component pads can induce additional RF
losses. It may be necessary to ask the PCB vendor to generate a new PCB stackup and
suggested trace width that is closer to the component pads, or modify the component pads
themselves
RF Trace Losses
RF Trace losses on a PCB are difficult to estimate without having appropriate tables or RF
simulation software. A good rule of thumb would be to keep the RF traces as short as possible,
make sure they are 50 ohm impedance, and don’t contain any sharp bends.
Figure 10-1 RF Trace Examples
.
Summary of Contents for SL876Q5-A
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