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Visitor
Posts: 3
Registered: ‎12-06-2017

Virtex 7 drop in for Virtex 5: 5% Voltage supply tolerance drop to 3%

Hello,

 

We are looking into replacing a Virtex 5 in a current design with a Virtex 7.  The main issue we are having is that the tolerance on the voltage supply has reduced from 5% to 3%.  Our point of load cannot meet 3%.  Is this a large concern and what should we expect to degrade?  If this is just a matter of applying derating, then we will likely move in this direction.  Are there and whitepapers that discuss this topic?

 

Thanks,

--Bobby

Xilinx Employee
Posts: 60
Registered: ‎08-25-2010

Re: Virtex 7 drop in for Virtex 5: 5% Voltage supply tolerance drop to 3%

Hi @robert.bowen,

 

p13-p14 discuss this topic in ug483:

https://www.xilinx.com/support/documentation/user_guides/ug483_7Series_PCB.pdf

 

 

Thanks

Simon

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Visitor
Posts: 3
Registered: ‎12-06-2017

Re: Virtex 7 drop in for Virtex 5: 5% Voltage supply tolerance drop to 3%

Hi Simon,

 

I just looked through the User Guide (UG483) and pages 13-14 discuss what capacitance is needed on each of the input voltages.  My question is more geared towards what will happen if I use a voltage supply of 1.0V plus or minus 5%.  The datasheet for Virtex 7 calls out a tolerance of 3%.  If I use 5%, what will be the consequences?  Can I apply derating to account for the additional 2% tolerance.

 

Thanks,

--Bobby

Voyager
Posts: 314
Registered: ‎01-08-2012

Re: Virtex 7 drop in for Virtex 5: 5% Voltage supply tolerance drop to 3%

[ Edited ]

robert.bowen wrote:
If I use 5%, what will be the consequences?  Can I apply derating to account for the additional 2% tolerance.

The datasheet says 3%.  Anything outside that is not guaranteed, although some aspects of the device might work just fine.  Think about words like "not guaranteed" and "might work" and match that against your customer's expectations.

 

But ... since you must be designing a new PCB (as I don't think there are any footprint compatible parts V5->V7), why not just design a PDN that can provide +/- 3% or better over your operating conditions?  DC/DC controllers as well as capacitors have improved greatly in the years between Virtex 5 and now.

 

Allan

Visitor
Posts: 3
Registered: ‎12-06-2017

Re: Virtex 7 drop in for Virtex 5: 5% Voltage supply tolerance drop to 3%

Thanks Allan!

 

One of the issues that I am having is that this is for a space application in the defense industry.  Finding a space grade solution to power the core 1.0V voltage may be tough.  Our point of loads are much closer to 5% where they worked along with the Virtex 5s.  I will start investigating solutions but am open to any suggestions.

Virtex 7 drop in for Virtex 5: 5% Voltage supply tolerance drop to 3%