DS320PR810: Differential Impedance

Fabio Gou

Part Number: DS320PR810

The description in the Datasheet of our DS320PR810 is a single-ended 50 ohm termination, but the current PCIe impedance is differential 85 ohm. Please help customer to confirm what they should choose when doing circuit design.

over 2 years ago

0 Nasser Mohammadi over 2 years ago

TI__Guru* 93670 points

Hi Fabio,

Typically if it is a chip to chip design then 100-ohm interface is used. However, in Add-In-Cards when signals go through 85-ohm impedance, 85-ohm controlled impedance is used. Therefor this depends on the customer application.

Regards, Nasser

0 Fabio Gou over 2 years ago in reply to Nasser Mohammadi

TI__Expert 4385 points

Can the high-speed signal pins of DS320PR810 be swapped to use? Because the customer’s pin definitions is reversed compared to our chip.

Which means the actual "N" will be connected to our "P" pin. The actual "P“ will be connected to our "N".

0 Nasser Mohammadi over 2 years ago in reply to Fabio Gou

TI__Guru* 93670 points

Hi Fabio,

PCIe is polarity in sensitive - meaning you can connect P to N or N to P - this is done for ease of pcb layout.

Regards, Nasser

0 Fabio Gou over 2 years ago in reply to Nasser Mohammadi

TI__Expert 4385 points

Hi Nasser,

Thanks for your support.

The customer have another question.

Because our redriver will enlarge the useful signal, how about the noise in the input side?

Whether there is technology in our product which would depress the enlarge function to noise signal?

Could you pls share related material with me?

Thanks

0 Nasser Mohammadi over 2 years ago in reply to Fabio Gou

TI__Guru* 93670 points

Hi Fabio,

Our redriver does not distinguishes between noise and incoming signal. Therefor if there is noise within the signal bandwidth we will amplify as well. PCIe specifications limits the noise from the source signal. As long as source signal is within the PCIe limit, then noise addition by the redriver is within 100fs.

Regards,Nasser

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DS320PR810: Differential Impedance