How the differential impedance calculated with out reference plane ?
kabaleeswaran , 03-14-2024, 04:19 PM
As i already discussed regarding differential pair impedance fedevel forum, Differential impedance to be maintained with the help of ground plane .but still i need to confirm few point in Magnetic Ethernet differential pair routing,How differential impedance calculated with out ground plane in Magnetic ethernet section. please check the below link. https://ww1.microchip.com/downloads/aemDocuments/documents/OTH/ProductDocuments/SupportingCollateral/LAN8742_QFN_Rev_A_Routing_Checklist.pdf
QDrives , 03-14-2024, 04:53 PM
I found this comment interesting:You can use a trace impedance calculator for stripline and just make the H (height above the ground plane) very large. But make sure you get the spacing between the diff pairs and their thickness (copper weight) correct.But it's going to high, probably over 100 ohms. Note that starts to look like a twisted pair configuration, that has a Zo of approximately 120 ohms.As to adding a ground plane, it should be connected to signal/power return. A picture of your connector and pin assignments would help.As was found here: https://electronics.stackexchange.com/questions/670006/differential-pairs-without-ground-plane
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