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Do you need magnetics for Ethernet?
Magnetics are part of the Ethernet specification for xBASE-T networks, and as such, they are required for all Ethernet enabled equipment. The magnetics protect against faults and transients, including rejection of common mode signals between the transceiver IC and the cable.
How does Ethernet magnetics work?
The magnetics allow different nodes on the Ethernet network to connect over long distances. It removes any connection issues created by different ground offsets at different nodes. The turns ratio on the coils is typically 1:1. The RJ45 connector is a standard connector format for Ethernet link.
What is an Ethernet transformer?
What is the purpose of the transformer? The primary purpose is isolation. Typically they are also used as part of the signal conditioning, turning a pair of single ended drives into a differential signal on transmit and establishing the correct common mode voltage for the receiver on receive.
Why transformers on Ethernet?
Transformers also provide common mode rejection which is useful for noise attenuation between the PHY device (transceiver IC) and the physical medium (cable). The first is to add an Ethernet magnetics module to your design’s PCB, between the PHY chip and the connector jack.
Are Ethernet ports isolated?
Ethernet offers galvanic isolation by design. All connections are transformed coupled. However this does not guarantee that no noise at all might creep into a networked device.
Are Ethernet cables grounded?
The general advice of wire manufacturers, and the general configuration of pre-manufactured cables, is for both ends to be grounded. This is contrary to common knowledge in electrical engineering regarding ground loops and the potential for lightning-induced current.
What does a PHY chip do?
Its purpose is to provide analog signal physical access to the link. It is usually interfaced with a Media Independent Interface (MII) to a MAC chip in a microcontroller or another system that takes care of the higher layer functions.
Is the PHY chip compatible with the RJ-45?
Commercially available transceivers are available with edge connectors or other connectors. This allows these transmitter/receiver modules to be swappable, ideally without taking apart an entire unit (e.g., hot-swappable interfaces). The routing requirements between the PHY chip and RJ-45 connectors are much more strict.
What kind of termination circuit does PHY use?
There is also a specific termination circuit that must be placed between the PHY and the RJ-45 connector, commonly termed “magnetics” within the Ethernet layout routing standards. A magnetics termination circuit involves four transformers for a single RF-45 connector, two on each RX and TX differential pair.
Where is the pull up resistor on a PHY?
The differential pairs should be impedance matched throughout the termination circuits (called Bob Smith termination), and the common method is to include a Thevenin network or a pull up resistor near the PHY. In this case, a portion of the power plane will need to appear near the pull-up resistor.