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JeffL

Zedboard 3.3V Aux

Question

I'm planning to attach a mezzanine card to the Zedboard via the board's ASP-134603-01 FMC connector.  I'm noting all of the 3.3V pins (VCC3V3) to provide power to the mezzanine card, and I noticed pin D32 of the FMC connector signal name is 3V3AUX.  I looked all over the datasheet and schematic, but I don't know what 3V3AUX is supposed to do.  Is pin D32 an additional pin that can provide 3.3V of power or is it an input pin that accepts 3.3V and it powers other circuitry on the development board?  Any help would be greatly appreciated.  Thanks.

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@JeffL

I have the older RevC version of the board so I can't address what you are looking at directly. I can say that you need to read the schematic for the board version that you have and figure out what the power supply pins on the FMC connector a connected to. On my board D32 is VCC3V3. Pins G39 and H39 are VADJ. The Vadj power supply is supposed to power the IO banks that are connected to the GPIO signals on the FMC connector. It should be adjustable to suit a particular IOSTANDARD that you want to use for these pins. There are a number of things to consider when connecting a board to your FMC connector before applying power.

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Hi @JeffL,

For the Rev D version of the board, this pin (D32 on the FMC) will also be a VCC 3.3V supply, much like it is for @zygot's Rev C. From the specification for VITA 57.1, this pin is "a 3.3V auxiliary power supple available for IO Mezzanine module use and is not intended to provide primary power to the module but rather to accommodate system management functionality which might need to operate even if the onboard power conversion circuitry fails." Based on rule 5.101 though, we (Digilent) have chosen to service this pin by using the main 3.3V line.

So, the short answer to your question is that the pin specifically on the Zedboard is a 3.3V source, though from my understanding this auxiliary supply should not be connected with any 3.3V primary paths on the mezzanine side.

Thank you,
JColvin

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