[802.3_ISAAC] Constraining the noise the PHY can output on the cable

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Subject: [802.3_ISAAC] Constraining the noise the PHY can output on the cable

From: Ragnar Jonsson <rjonsson@xxxxxxxxxxx>

Date: Thu, 31 Jul 2025 07:47:54 +0000

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Reply-to: Ragnar Jonsson <rjonsson@xxxxxxxxxxx>

Thread-index: AdwB7tWu9z4v2wDwQve/RbMRoDo5gg==

Thread-topic: Constraining the noise the PHY can output on the cable

All,

In the 802.3dm meeting yesterday Ahmad Chini presented

https://www.ieee802.org/3/dm/public/0725/Chini_3dm_01b_07272025.pdf

In the discussion of this presentation, it was pointed out that the 1uH inductor might not provide sufficient isolation from PMIC noise coupling into MDI (connector) and into the PHY.

The enclosed presentation shares a high-level analysis of the signal transfer functions on the PCB board when using single 1uH inductor.

Based on the enclosed analysis I think that the Task Force should consider constraining the noise the PHY can output on the cable.

Ragnar

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Attachment: On 1uH PoC Inductor - 20250731.pdf
Description: On 1uH PoC Inductor - 20250731.pdf