DS80PCI102: redriver placement question

Terry Wu2

Expert 2110 points

Part Number: DS80PCI102

Hello Sirs,

We have a application for a PCIe GEN1 x1 from CPU to BMC .

Total 20 inch exceed CPU spec (16") . If we plan to put redriver DS80PCI102.

Do you have placement suggestion ? EX:

CPU 10" => PCI102 => BMC or others you prefer ?

Refer to datasheet table 2 EQ setting, ds80pci102 support up to 35" 4 mil trace width .(LEVEL 10)

Refer to table 3 . Output support 20" 4 mil trace width (LEVEL 12)

www.ti.com/.../ds80pci102.pdf

How to consider path from BMC to CPU ?

TKS your help in advance!

over 6 years ago

0 Lee Sledjeski over 6 years ago

TI__Mastermind 43795 points

Hi Terry,

I agree with your placement plan to put the DS80PCI102 in the middle of the 20" channel.

I would recommend to set the input and output equalization at a lower level than the datasheet tables since PCIe gen1 usually uses ~ -3.5dB of de-emphasis on the system Tx pairs.

DS80PCI102 settings.

Input (Rx)

EQ = Level 1 (3.4 dB of gain)

Output

VOD/DEM = Level 3 (- 3.5dB)

Regards,

Lee

0 Terry Wu2 over 6 years ago in reply to Lee Sledjeski

Expert 2110 points

Hello Lee,

Many thanks your suggestion !

Is there guideline to determine DE / VOD for Tx output trace length ?

TKS ~

0 Lee Sledjeski over 6 years ago in reply to Terry Wu2

TI__Mastermind 43795 points

PCIe gen1 usually uses 1.0 VOD and -3.5 dB DEM. This is a good place to start.
Regards,
Lee

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DS80PCI102: redriver placement question