Powering unused MGTs in XC4VFX20CES2

Hi!

I just read the Virtex 4 documentation and the errata sheet for the XC4VFX20CES2 device and I'm thinking about one aspect I found while designing a PCB.

My design will not use any one of the included MGTs. I found in the Xilinx answer database that even unused MGTs need to be powered. Here, the AVCCAUXTRX/RX voltage in the errata sheet is 1.1V while it is -0.5

- 1.32 in the V4 datasheet.

Since I have a supply for VCCINT with 1.2V on my board, I'm wondering if 1.1V are only neccessary to power used MGTs, while 1.2V can be used to power unused MGTs in the CES2 device ??

Thanks, Peter

Btw.: Do I need any filtering?

Reply to
Peter Rauschert
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Sorry, I forgot to ask another question. Since I'm using the ES2, the transceiver pins for MGT_110 are not available.

Do I also need to power this MGT_110 with the suggested voltage?

Thanks, Peter

Reply to
Peter Rauschert

Peter,

The requirement to power unused MGTs is to meet ESD performance. If the power and ground pins are left unconnected (to the MGT), it is unknown what the ESD protection performance will be (basically, it is not tested that way).

The voltage can be 1.2V (no issue with 1.1V, as you are not using the MGTs).

Also, filtering is not required (as they will not actually be enabled).

If one MGT is left unpowered, be sure the ground supply pin is connected to ground, at a minimum.

Aust> Hi!

Reply to
Austin Lesea

The powering requirements for unused MGTs are to make sure that everything on the part is in a known state. This means that you can cut some corners for these MGTs. You can safely power the AVCCAUXTX and AVCCAUXRX from your VCCINT 1.2V supply and not the 1.1V and you don't need any power filtering on these pins.

You comment regarding 1.1V in the current errata vs -0.5 to 1.32V in the V4 datasheet is a mistake. The former is for AVCCAUXTX/RX and the later is only for the VTRX supply.

Ed

Reply to
Ed McGettigan

Yes you need to power this transceiver as well.

Ed

Reply to
Ed McGettigan

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