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TDA4VH-Q1: SGMII AC capacitor placement

SH
Intellectual 400 points
Part Number: TDA4VH-Q1

Tool/software:

What is TI's recommendation on placing the AC coupling capacitors on the SGMII Rx- and Tx-lines with TDA4VH-Q1?

In similar topics for some other parts the recommendation seems to be placing the AC capacitors near the Tx.

DS90UB983-Q1: The reason why AC capacitor should place very close to transmitter pin - Interface forum - Interface - TI E2E support forums

DP83TC811S-Q1: SGMII AC capacitor placement - Interface forum - Interface - TI E2E support forums

But in EVM design (PROC141E5) the capacitors on Tx-lines, for example R653 and C647, are close to connector on the board and not close to the SoC (Tx) pins.

  • 0
    TI__Guru 62160 points

    SH,

    I think it makes sense to have the capacitor near the TX pins to negate the effects of transients. The placement of the caps should not be on the far-end.

  • 0 in reply to ShreyasRao
    TI__Guru 52265 points

    Functionally - it doesn't matter.  The incoming signal must be AC-Coupled to the receiver (removes any incoming DC voltage offset).  This can be done anywhere in the connection.  The linked E2E comments  suggest placing near transmitter for some SI (signal integrity) benefit.   It is possible placing near source could help minimize SI impact of capacitors, but also could be system/PCB dependent.