VDDIOT voltage

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Dmil
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VDDIOT voltage

Postby Dmil » Fri May 12, 2017 12:09 pm

XE216-512-TQ128 Datasheet
P.21
If the PHY supports a 3.3V IO voltage, then a 3.3V supply can be used for VDDIOT.
P.23
The signal description (Section 4) specifies which I/O is powered from
which power-supply VDDIOT powers the RGMII IO pins, and must be provided
with 2.5V.
P.29
Both VDDIOT 3v3 and VDDIOT 2v5 characteristics.
P.77
VDDIOT has a 2.5V supply.

Is it possible using 3.3 V supply?
Must VDDIOT be powered even if RGMII interface is not used or it can be left unconnected ?
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Bianco
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Postby Bianco » Fri May 12, 2017 1:21 pm

You can power VDDIOT with 3V3.
I would not leave it unpowered, most likely you will use some pins powered by VDDIOT anyway.
Dmil
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Postby Dmil » Fri May 12, 2017 1:25 pm

We don't need VDDIOT. Is it good for CPU if VDDIOT will be left unpowered?
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Bianco
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Postby Bianco » Fri May 12, 2017 2:35 pm

Not connecting power rails in the general case is always a bad idea and can lead to undefined behaviour unless explicitly stated by the manufacturer that you can leave it unconnected. So I would just connect them, its only two pins only and they are adjacent to each other too.

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