AM5728: PCIe layout question

matusan

Guru 10235 points

Part Number: AM5728

Hello, TI Experts,

Our customer sent us a question about AC-Coupling Placement for PCI Express Layout.

Question

Is there any restriction or recommendation for AC-Coupling Capacitor placement of PCI Express?

(Is there any recommended distance from the PCI express pins of AM5728?)

We found the related description from "Figure 19. AC-Coupling Placement" of the document as below.

http://www.ti.com/lit/an/spraar7f/spraar7f.pdf

But we cannot find specific value of the distance for AC-Coupling Capacitor placement.

We would appreciate if you tell us the recommended distance from the PCI express pins of AM5728.

Best regards,

over 7 years ago

0 Biser Gatchev-XID over 7 years ago

TI__Guru**** 393215 points

Hi,

There is no specific requirement for this. On the AM572x GP EVM the decoupling capacitors are placed close to the TX pins.

0 -DK- over 7 years ago

TI__Mastermind 27860 points

From the PCI-Express Base Specification:

Capacitors must be placed on the Transmitter side of an interface that permits adapters to be plugged and unplugged. In a topology where everything is
located on a single substrate, the capacitors may be located anywhere along the channel.

0 matusan over 7 years ago in reply to -DK-

Guru 10235 points

Hi,

Thank you very much for your kindness.
I really appreciate your help.

Best regards,

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AM5728: PCIe layout question