Cypress S6J3200 Series Manuallines - Página 4

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3.3

Physical Length / Delay Matching

The physical length of the traces that form each balanced transmission line, and how well they are matched,

determine much of the signal integrity and timing margin of the interface. Length matching must be managed both

between the true and complement traces that form each balanced transmission line (L

balanced transmission lines (L

signal into common-mode, and the differences in delay of each transmission line between the source and destination.

Figure 4

shows three differential pairs routed between the sending device (S6J3200) and a connector, and how

routing can introduce differences in physical length.

Of the three balanced transmission lines shown in

length within the balanced pair (L

should be acceptable.

TxDOUTx+ and TxDOUTx– signals, and this should be avoided.

When routed as a balanced microstrip on FR4, each millimeter of length equates to approximately 10 ps of delay

and every millimeter of length difference between traces equates to a time offset of 10 ps. When there is a difference

in length between the true and complement traces of a balanced transmission line, the electromagnetic field between

For microstrip transmission lines in FR-4 with a dielectric constant of 4.7

www.cypress.com

Figure 3. Balanced Transmission Lines Spacing

PCB

). The matching of physical length is used to limit the conversion of a differential

Figure 4. Physical Length

Connector

S6J3200

Figure

). The TxDOUTz± signal has some mismatch, but in most of the cases, this

The TxDOUTy± signal, however, has a large difference in trace length between the

Document No. 002-11139 Rev. *A

FPD-Link PCB Guidelines for the Traveo Family S6J3200 Series MCUs

< 5 mm

is the difference between the length

of differential

DIF+/DIF–

(TxDOUTy) and

other differential

DIF+/DIF–

< 5 mm

is the difference between the length

of the true and complement signals of

any differential signal (TxDOUTx).

4, the TxDOUTy± signal has the best matching of trace

) and between different

(TxDOUTz).

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