Table of Contents
Advertisement
2.1.1
Implementation Notes
Examine the specific interface loss budget definition. Calculate or simulate the end-to-end loss
and take into account:
•
Insertion loss of board traces.
•
Insertion loss of any component the signal travels through, including connectors, AC coupling
capacitors, and cables.
Properly select trace geometrical dimensions and choose the suitable material to assure
achieving a predefined amount of end-to-end loss.
Wider traces are characterized by lower skin effect. Final manufactured trace width may be
narrower than the planned and may influence skin effect. Monitor the actual manufactured trace
width. Recalculate the loss using the actual manufactured width and verify that it meets the
insertion-loss budget at the predefined frequencies.
The µ-strip (outer layer) is characterized by lower dielectric loss compared to the strip line (inner
layer) and usually requires fewer vias. However, the µ-strip is usually characterized by higher
copper surface roughness and high-impedance fluctuations. Consider using core material for
µ-strips.
Monitor the material loss coefficient and the dielectric constant parameter during manufacturing.
Verify that there are a consistent loss coefficient and dielectric constant over material batches.
Verify that the insertion-loss curve shape is smooth.
•
Avoid stubs on high-speed serial interface traces and limit the maximal via stub length.
•
Minimize the number of vias along a high-speed serial link differential pair.
•
Minimize discontinuities caused by trace impedance and parasitic capacitance.
Note
Copyright © 2017 Marvell
August 30, 2017
For Electromagnetic interference (EMI) issues related to using µ-strip routing, see
AN-216, EMI Guidelines.
Document Classification: Public
Generic Guidelines for SERDES Interfaces
Insertion Loss and Loss Budget
Doc. No. MV-S302310-U0 Rev. A
Page 11
Advertisement
Table of Contents
