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Re: [802.3_B10GAUTO] AC coupling capacitors information

Chris – First, remember that link segment does not equal cable.  A link segment is the transmission path between the two MDIs, which may contain connectors, filters, and other passive devices.

While it might be tempting to add a qualitative statement as below, adding such a paragraph is technically meaningless. It provides nothing that can be evaluated. For example – is that only specifying a zero-frequency null? To what depth?  After what frequency should the exponential be held?  Under a constraint like that, you could have a band-stop filter starting at 10 MHz (say, if you wanted a mid-span Power injector). That is why the lower frequency bound is important – it provides technical clarity on the performance that a PHY implementer can expect of the link segment.  I think that German’s point is quite valid, and have seen examples where assuming that the link segment would be well behaved (rather than specifying it) causes problems for PHYs, such as those German describes.

-george

From: Christopher T. Diminico <00000025925d7602-dmarc-request@xxxxxxxxxxxxxxxxx>
Sent: Monday, January 17, 2022 9:15 PM
To: STDS-802-3-B10GAUTO@xxxxxxxxxxxxxxxxx
Subject: Re: [802.3_B10GAUTO] AC coupling capacitors information

 

Haysam et al,  

 

The link segment is not AC-coupled. We can explicitly preclude AC-coupling in the link segment by adding a sentence for those concerned of 

the possibility. 

 

165.7 Link segment characteristics - 

Add sentence end of paragraph

AC-coupling shall not be implemented within 

the link segment (between TP1 and TP4).


The link segment IL limit should not be changed from 10MHz to 2MHz on the basis of baseline wander attributed to HPF corner frequency in https://www.ieee802.org/3/cy/public/nov21/feyh_3cy_01b_01_11_09_21.pdf.

 


Regards, Chris



-----Original Message-----
From: Haysam Kadry <hkadry@xxxxxxxx>
To: STDS-802-3-B10GAUTO@xxxxxxxxxxxxxxxxx
Sent: Tue, Jan 11, 2022 9:50 pm
Subject: [802.3_B10GAUTO] AC coupling capacitors information

Hello, 

 

The discussion in moving the IL limit from 10MHz to 2MHz in accordance to https://www.ieee802.org/3/cy/public/nov21/feyh_3cy_01b_01_11_09_21.pdf.  I am looking for some information 

 

1. AC couple capacitor value range and ESR characteristics.

2. PHY termination circuit values 

 

This will help put together a simulation profile for the front end circuit.  

 

Best regards, 

 

Haysam M. Kadry

Ford Motor Company

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