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Can anyone explain why these connections (highlighted in pink) are done like this and how it works on the Olimex EVB ESP32 with Ethernet?

I want to design a custom ESP32 with Ethernet board but I am absolutely new to Ethernet. I have already started looking for reference designs and started to understand them but this part is confusing.

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  • \$\begingroup\$ The pink line controls power and clock to Ethernet. So it does not really relate to Ethernet itself, but board power management, managing the Ethernet power. What specifically you want to know about it? \$\endgroup\$
    – Justme
    Dec 2, 2022 at 10:01
  • \$\begingroup\$ Why we are controlling the power can't we just power both IC at once?also why we are giving crystal to ESP as well?@Justme \$\endgroup\$
    – navi
    Dec 3, 2022 at 13:30
  • \$\begingroup\$ That is a good guestion. We can only guess as we are not the designers of the circuit. You can keep the whole circuit powered up all the time. But if you put the MCU into sleep mode to save power, where it can't communicate with Ethernet anyway, it might be a good idea to save power by turning the whole Ethernet side off if you don't need it. \$\endgroup\$
    – Justme
    Dec 3, 2022 at 13:39

1 Answer 1

Reset to default
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The OSC_DIS controls the NRST line, the phy must be kept in reset for 25ms after power comes up:

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Source: https://www.mouser.in/datasheet/2/268/00002164B-977414.pdf

It's also unclear why they tie the RST line to the clock, because the datasheet says they need to keep the clock running while the reset is low.

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  • \$\begingroup\$ Yeah also why they are giving external crystal to ESP? \$\endgroup\$
    – navi
    Dec 3, 2022 at 13:32
  • \$\begingroup\$ Because then you only need one Crystal and not two or three that saves money and space \$\endgroup\$
    – Voltage Spike ♦
    Dec 3, 2022 at 15:27
  • \$\begingroup\$ Can you explain if possible how NCP303LSN27T1G and VDA2710NTA is working here? \$\endgroup\$
    – navi
    Dec 4, 2022 at 15:35
  • \$\begingroup\$ It looks like they could use that for a reset also, I'll bet only either the NCP303 or the VDA2710 is loaded and not both as they do the same function \$\endgroup\$
    – Voltage Spike ♦
    Dec 4, 2022 at 17:43
  • \$\begingroup\$ But according to circuit both are working together but i don't understand the necessity for both. \$\endgroup\$
    – navi
    Dec 5, 2022 at 4:39

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