DP83867CS datasheet(113/129 Pages) TI2

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When operating in three-supply mode, the 1.8V VDDA1P8 supply must be stable within 25ms of the 2.5V

VDDA2P5 supply ramping up. There is no sequencing requirement for other supplies when operating in three-

supply mode.

When powering down the DP83867, the 1.8V supply must be brought down before the 2.5V supply.

VDDA1P8

VDDA2P5

Figure 8-9. Three-Supply Mode Power Supply Sequence Diagram

Table 8-5. Three-Supply Mode Power Supply Sequence

PARAMETER

TEST CONDITIONS

MIN

NOM

MAX UNIT

Beginning of VDDA2P5 ramp up

to VDDA1P8 stable

Note

If the 2.5V power supply provides power to DP83867 devices only, the 1.8V supply can ramp up any

time before 2.5V.

There is no requirement for the sequence of the supplies when operating in two-supply mode.

8.4 Layout

8.4.1 Layout Guidelines

8.4.1.1 Signal Traces

PCB traces are lossy and long traces can degrade the signal quality. Traces must be kept short as possible.

Unless mentioned otherwise, all signal traces must be 50Ω, single-ended impedance. Differential traces must

be 50Ω single-ended and 100Ω differential. Take care that the impedance is constant throughout. Impedance

discontinuities cause reflections leading to EMI & signal integrity problems. Stubs must be avoided on all signal

traces, especially the differential signal pairs. See Figure 8-10

Within the differential pairs, the trace lengths must run parallel to each other and matched in length. Matched

lengths minimize delay differences, avoiding an increase in common-mode noise and increased EMI.

Length matching is also important on MAC interface. All Transmit signal trace lengths must match to each other

and all Receive signal trace lengths must match to each other.

There must be no crossover or via on the signal paths. Vias present impedance discontinuities and must be

minimized when possible. Route an entire trace pair on a single layer if possible.

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DP83867CS, DP83867IS, DP83867E

SNLS504F – OCTOBER 2015 – REVISED JANUARY 2025

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DP83867CS Datasheet(PDF) 113 Page - Texas Instruments