Virtex 4 Power consumption

Can anyone give me an estimate of the max current a V4fx60 FPGA will
draw for VCCINT @ 1.2v, & VCCAUX and VCCO @ 2.5v?

I am designing a board with 9 of them and need a rough idea of power
required.

Any help would be appreciated.

Jason

Using the Xilinx XPower tool, you can get an estimate of the worst case
power consumption. If you just crank in 1.2v for VCCINT and 2.5v for
VCCO, then by a simple division, you could get the max current drawn by
a V4FX60 FPGA for a specific design. Different designs will draw
different amounts of current. 

Amr

XPower says I need a completely mapped NCD file to get started.  I dont
have anything from the FPGA designer that I can use yet.

Can I do anything without requiring the NCD file?

Jason

Jason,

Use the on line power estimator tool.

Less accurate, but it should allow you to get a good feeling for the 
power needed for you design.

Austin

jason.stubbs wrote:

> XPower says I need a completely mapped NCD file to get started.  I dont
> have anything from the FPGA designer that I can use yet.
> 
> Can I do anything without requiring the NCD file?
> 
> Jason
> 

Austin,

The online tool also requires details of the design that I dont have.
Can you guide me in what I have to enter to estimate the worse case?

Thanks

Jason

Jason,

The 'worst case'?  For a FPGA the 'worst case' is probably something you 
don't even want to consider.

For example, if you put in all 100% of the CLB FF's toggling at 300 MHz, 
you are likely to see that the power required is so large that you can 
not heatsink the device (would melt the solder and fall off the pcb).

The power estimators need your case, not the 'worst case'.

Austin

jason.stubbs wrote:

> Austin,
> 
> The online tool also requires details of the design that I dont have.
> Can you guide me in what I have to enter to estimate the worse case?
> 
> Thanks
> 
> Jason
> 

>> The online tool also requires details of the design that I dont have.
>> Can you guide me in what I have to enter to estimate the worse case?

Make some estimates or guesses.  That will at least give you a number.

Then go back and change the numbers you aren't sure about.  If the
answer doesn't change much then don't worry much.  If the answer
depends a lot on your wild guesses then you have learned
that you have to work on that part of the design so you will have
meaningful numbers to feed to the power-estimator.

-- 
The suespammers.org mail server is located in California.  So are all my
other mailboxes.  Please do not send unsolicited bulk e-mail or unsolicited
commercial e-mail to my suespammers.org address or any of my other addresses.
These are my opinions, not necessarily my employer's.  I hate spam.

Hi Jason,

"jason.stubbs" wrote:

> Austin,
>
> The online tool also requires details of the design that I dont have.
> Can you guide me in what I have to enter to estimate the worse case?

In terms of "PVT" - Process, Voltage & Temperature : In the WPT currently
you can, for V4 FX devices, vary Vccint and the ambient temperature.
That partially addresses the "V" & "T".

On the "P" or process side here are a few guidelines :
- if you are at worst case process and worst case voltage (1.3 V) you
should use a factor of 2.5.
- if you are at  worst case process but at nominal voltage you should use
a 2.0 factor.

Brendan


>
>
> Thanks
>
> Jason

Hi Brendan,

> In terms of "PVT" - Process, Voltage & Temperature : In the WPT currently
> you can, for V4 FX devices, vary Vccint and the ambient temperature.

When I enter 1.25V vs. 1.20V in WPT 4.1, I'm given 687 mW vs. 660 mW of 
VccInt static power for a LX80, in addition to the 234 mW of VccAux power.

Similarly, for some random amount of logic utlization, I get 2727 mW vs. 
2618 mW of dynamic power.

It seems to me that all the tool is doing is increasing the V in P = VI. 
However, increasing V should (a) increase dynamic current draw roughly 
linearly and (b) increase sub-threshold leakage by the square of 1.25/1.2. 
Neither of these effects appear to be modeled.

Regards,

Paul Leventis
Altera Corp.

Paul,

Since we power the pass gates from Vccaux through a band gap referenced 
supply for the entire interconnect, many simple minded formulas that you 
may come up with will not apply.

Austin

Paul Leventis (at home) wrote:

> Hi Brendan,
> 
> 
>>In terms of "PVT" - Process, Voltage & Temperature : In the WPT currently
>>you can, for V4 FX devices, vary Vccint and the ambient temperature.
> 
> 
> When I enter 1.25V vs. 1.20V in WPT 4.1, I'm given 687 mW vs. 660 mW of 
> VccInt static power for a LX80, in addition to the 234 mW of VccAux power.
> 
> Similarly, for some random amount of logic utlization, I get 2727 mW vs. 
> 2618 mW of dynamic power.
> 
> It seems to me that all the tool is doing is increasing the V in P = VI. 
> However, increasing V should (a) increase dynamic current draw roughly 
> linearly and (b) increase sub-threshold leakage by the square of 1.25/1.2. 
> Neither of these effects appear to be modeled.
> 
> Regards,
> 
> Paul Leventis
> Altera Corp.
> 
>