AM69A: Question About PCIe Clock Source in AM69A EVM PROC154E3_RP Circuit

Gary Yu

Part Number: AM69A
Other Parts Discussed in Thread: TDA4VH, AM69

Tool/software:

Hi Sir,

I observed that all the PCIe clocks in the PROC154E3_RP circuit are sourced from a clock buffer rather than using the SoC’s PCIE_REFCLK_OUT.

Could you explain the reason for this design choice?

Additionally, is it possible to design the circuit using the SoC’s PCIE_REFCLK_OUT instead of an external clock buffer?

Are there any limitations or considerations we should be aware of when using the SoC’s clock output?

Thank you.

Best regards,

Gary Yu

7 months ago

0 Takuma Fujiwara 7 months ago

TI__Guru 51803 points

Hi Gary,

Yes, it is possible to design without using an external clock. PCIe1 on J784S4 EVM for PROC141E4_RP that can be downloaded from here under "Design files" is an example: https://www.ti.com/tool/J784S4XEVM

As in the TRM, AM69/J784S4/TDA4VH are hardware-wise mostly the same, so the design for J784S4 EVM can be used for the PCIe clock.

As for limitations, the software is a bit more complex to set up than using an external clock, and there is a potential to hit an errata. Specifically, errata i2242: https://www.ti.com/lit/er/sprz536b/sprz536b.pdf?ts=1739382083270&ref_url=https%253A%252F%252Fwww.google.com%252F

Regards,

Takuma

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AM69A: Question About PCIe Clock Source in AM69A EVM PROC154E3_RP Circuit