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Observer
Observer
3,752 Views
Registered: ‎04-29-2008

On -1L / -2L devices, can the voltage be adjusted "on the fly" to choose performance vs. power?

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Hello all,

 

On the -1L and -2L devices, which are designed to run at 0.9v, the user has the option of choosing the performance by selecting the voltage applied to the rails.  However, is it allowed to adjust the voltage of the rails during run-time, thus enabling the user to boost the voltage to get extra performance when needed?

 

Obviously the design would have to meet timing for the higher speedgrade, but the convenience of being able to put the whole device into a lower power state when maximum performance is not required is still sought by the customer.

 

Any experience here please?  All wisdom is welcomed.

 

Thanks,

Rich

 

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austin
Scholar
Scholar
4,708 Views
Registered: ‎02-27-2008

Rich,


In a word:  yes.


As long as the voltage is between 0.0v and 1.0v, you may move it around all you like.  Yes, obviously you need to be able to meet timing at 0.9v for the design when it is running at that voltage.  Similar for timing at 1.0v.

 

I would caution that usage of the DCM (PLL) may require resets to those blocks after an adjustment (they may lose lock).

 

I have perfomed many tests where I continuously adjusted the Vccint from 1.1v down to where the device hit the power on reset threshold (usually somewhere around 0.5-0.7v).  The trick to not upsetting the DCM is to do so slowly (I changed the voltage over periods lasting perhaps a few seconds, allowing it to track and not lose lock).

Austin Lesea
Principal Engineer
Xilinx San Jose

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austin
Scholar
Scholar
4,709 Views
Registered: ‎02-27-2008

Rich,


In a word:  yes.


As long as the voltage is between 0.0v and 1.0v, you may move it around all you like.  Yes, obviously you need to be able to meet timing at 0.9v for the design when it is running at that voltage.  Similar for timing at 1.0v.

 

I would caution that usage of the DCM (PLL) may require resets to those blocks after an adjustment (they may lose lock).

 

I have perfomed many tests where I continuously adjusted the Vccint from 1.1v down to where the device hit the power on reset threshold (usually somewhere around 0.5-0.7v).  The trick to not upsetting the DCM is to do so slowly (I changed the voltage over periods lasting perhaps a few seconds, allowing it to track and not lose lock).

Austin Lesea
Principal Engineer
Xilinx San Jose

View solution in original post

q
Observer
Observer
3,722 Views
Registered: ‎04-29-2008
Great, thanks Austin.

Kind regards,
Rich
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