General
Review and verify the following for
the custom schematic design:
- Above sections, including
relevant application notes and FAQ links.
- Pin attributes and signal
description.
- Electrical characteristics,
timing parameters, and any additional available information.
- MAC interface configuration
and recommended connections including series resistors (on the TDn signals
near to processor MAC TDn output pins and optional 0Ω series resistor near
the attached device).
- IO level compatibility
between processor MAC and EPHY (attached device). The attached device IO
supply and the IO supply group (IO supply rail) VDDSHV2 referenced by the
interface signals are recommended to be connected to the same supply
source.
- Matching of processor and
EPHY clock specifications.
- Clocking of EPHY and
processor MAC including addition of buffers based on the EPHY configuration
and clock architecture (use of common Oscillator and Buffer or RMII
interface). When the clock output connects to more than one inputs, each of
the clock inputs must be buffered using individual buffers.
- Interface connections, IO
level compatibility, fail-safe operation (when MACs are powered by different
power sources) and matching of clock specifications when MAC-to-MAC
interface is used.
- MDIO interface connection
including pullup for MDIO data added near to the EPHY. MDIO connection to
multiple devices and the addition of pullup near each EPHY.
- When 2 EPHYs are used,
configuration of EPHY device address to read the internal registers through
the MDIO interface.
- Implementation of EPHY reset
logic. When 2 EPHYs are used, the recommendation is to provide provision to
reset the EPHYs individually when used for boot a 2-3 input ANDing logic can
be used.
- In case implementing an
Ethernet boot is required, verify the errata, supported EPHY interface
configurations, MAC interface port used versus recommended, and the
recommended clock and interface connection.
Schematic Review
Follow the below list for the custom
schematic design:
- Provision for series resistor
for the processor MAC transmit signals TDx near to the processor output
pins
- Verify the EPHY reset
implementation including ANDing logic, EPHY reset input pull and compare
with SK as required
- Verify EPHY device address
configuration when 2 EPHYs are used and MDIO interface is required
- Verify the IO level
compatibility - the attached device IO supply and the IO supply group (IO
supply rail) referenced by the processor interface signals are connected to
the same supply source
- Compare the bulk and
decoupling capacitors used for all the EPHY supply rails with SK schematics
when TI EPHY is used
- Pullup is populated for
processor GPIO input of the EPHY reset ANDing logic
- Pullup on the MDIO clock may
not be allowed (EPHY may have internal pulldown - verify in the data
sheet)
- Supply rails connected follow
the ROC
Additional
- Follow the below steps when using TI EPHY:
- Get the EPHY implementation reviewed by the
relevant BU/PL
- Verify the power sequence requirements for
two-supply configuration and three-supply
configuration
- Verify the RBIAS resistor tolerance as per the
EPHY data sheet
- Selection of the RJ45 connector with integrated
magnetics, follow SK
- Provision for external ESD protection for the MDI
signals
- Connection of RJ45 connector shield to circuit
ground
- The recommended bulk and decoupling capacitors
are provided (refer SK as required)
- Use a single output, individual
buffer device, or dual or multiple output buffer to connect the clock output of
the oscillator to the processor and EPHYs. For specific use case (requirement
for some of the industrial applications using a Time Sensitive Networking (TSN))
input and two or more output (based on number of EPHYs used) buffer is
recommended for the processor and the EPHYs.
- When EPHY is configured as RMII
slave (peripheral), two-output phase aligned buffer with a common input is
recommended.
- If space is not a constraint,
consider adding 0Ω series resistors on the RX signals near to the EPHY.
- ANDing logic additionally
performs level translation. Verify the reset IO level compatibility before
optimizing the reset ANDing logic. IO level mismatch can cause supply leakage
and affect processor operation.
- To simplify the ANDing logic, use
a 2-input AND gate with RESETSTATz and the processor IO as inputs.
- Verify design recommendations as
per the data sheet or EVM implementation are considered for the attached device,
including terminations and external ESD protection.