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Message
From: "Martin.J Thompson" <Martin.J.Thompson@t...>
Date: Thu, 27 Nov 2003 08:28:40 +0000
Subject: Re: [oc] OT : FPGA price
>On Thu, 2003-11-27 at 02:10, Martin.J Thompson wrote:
>> >On Tue, Nov 25, 2003 at 10:54:27AM +0000, Martin.J Thompson wrote:
>> >> >-no 2A power up spike,
>> >>
>> >> None of that in V-II or Spartan-III
>> >
>> >the virtex's are specified to draw a big power-on surge actually.
>>
>> Correct Virtex, Virtex-E, Spartan-II and SpartanIIe, and probably Spartan-XL.. Not Virtex-II
>> Also, All the Altera FPGAs as far as I know exhibit this behavoiur, but its less well documented.
>>
>
>I was not aware (as I didn't look) the virtex II had eliminated surge.
>
>The VII-pro has it back again, specified only for a particular power
>sequencing, although with the statement that alternate power sequencing
>is not destructive. The smallest one (v2p4) was in the half amp range
>from memory.. Just vague enough I had to add supply sequencing to ensure
>supplies came up ordered.There was not a big margin there.
>
According to the answers database, "There is no power sequencing requirement for Virtex-II/ Virtex-II Pro", Record Number: 10989 Last Modified: 08/21/03... do you have more recent information from them?
>>
>> Tjmax is what matters to whether your design works or not. If you have a single FF toggling at 1Hz you can probably run in an ambient close to Tjmax. In a big
>design all clocking fast, your maximum allowable ambient temperature is lower for the same Tjmax. That's why there no point any vendor quoting me a Tambient
>max. They know nothing of my design.
>>
>
>This is true.
>device reliability (FIT) becomes a concern too.
Indeed, and Xilinx have lots of numbers for that as well.
>My response was only to emphasize although its tjmax that matters, for
>timing reasons, that the ambient enters into the calculation.
>Specifying max ambient would only make sense if the device power
>consumption is a constant. Hey - just like those early-eighties PLDs.
>
Sounds like we're agreed ont hat then - I had initially read your comment to imply that the other vendors devices were 'better specified' due to their specifying a Tamb(max) for the device - sorry abnout that!
Cheers,
Martin
--
Martin Thompson CEng MIEE
TRW Conekt
Stratford Road, Solihull, B90 4GW. UK
Tel: +44 (0)121-627-3569 - martin.j.thompson@t...
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