When creating a new system design with an Ethernet PHY, follow this schematic capture procedure:
- Select desired PHY hardware configurations in Table 7-17.
- Use the Section 6.5 table and Table 7-16 to select the correct external bootstrap resistors.
- If using LEDs, make sure the correct external
circuit is applied as shown in Figure 7-15.
- Select an appropriate clock source that adheres
to either the CMOS-level oscillator or crystal resonator requirements within the
Section 6.5
table.
- Select a CMC, a list of recommended CMCs are located in Table 8-2.
- Add common-mode termination, DC-blocking capacitors, an MDI-coupling capacitor, and an ESD shunt found in Table 8-1.
- Make sure that there is sufficient supply
decoupling on VDDIO and VDDA supply pins.
- Add an external pullup resistor (tie to VDDIO) on MDIO line.
- If operating with
SGMII, place 0.1μF, DC-blocking capacitors between the MAC
and PHY SGMII pins.
- If sleep modes are not desired, WAKE and EN pins
must be tied to VDDIO directly or through an external pullup
resistor.
The following layout procedure needs to be
followed:
- Locate the PHY near the edge of the board so that short MDI traces can be routed to the desired connector.
- Place the MDI external components: CMC, DC-blocking capacitors, CM termination, MDI-coupling capacitor, and ESD shunt.
- Create a top-layer metal pour keepout under the CMC.
- Make sure that the MDI TRD_M and TRD_P traces are
routed so that they are 100Ω differential.
- Place the clock source near the XI and XO pins.
- Make sure that when configured for MII, RMII, or
RGMII operation, the xMII pins are routed 50Ω and are
single-ended with reference to ground.
- Make sure that transmit path xMII pins are routed
such that setup and hold timing does not violate the PHY
requirements.
- Make sure that receive path xMII pins are routed
such that setup and hold timing does not violate the MAC
requirements.
- Make sure that
when configured for SGMII operation, the xMII RX_P, RX_M,
TX_P, and TX_M pins are routed 100Ω differential.
- Place the MDIO pullup close to the PHY.