On May 13, 1:45*pm, Mike Harrison <m...@whitewing.co.uk> wrote:
> On Wed, 13 May 2009 03:58:40 -0700 (PDT), "Antti.Luk...@googlemail.com"
>
>
>
> <Antti.Luk...@googlemail.com> wrote:
> >On May 13, 1:23*pm, Mike Harrison <m...@whitewing.co.uk> wrote:
> >> I'm looking at a possible application and trying to figure the relative costs of FPGA/CPLD versus
> >> MCU.
> >> I can do it with a microcontroller, but the only MCUs with the hardware I need (TFT LCD controller)
> >> tend to come with lots of other stuff (ethernet, large flash, USB etc.) which I don't need.
>
> >> As it can be hard to get 'real' prices of FPGAs without talking to allthe distis etc. I *wonder if
> >> anyone can suggest parts to look at .
>
> >> Rough reqiurement is :
>
> >> Cheapest in 100x qtys for total solution inc. config and power supply ( from 3.3v supply), below
> >> about GBP5(US$7.5)
> >> Not BGA
> >> Readly available : ex-stock or sensible leadtimes (2 weeks)
> >> A couple of RAM blocks, around 1K byte each
> >> about 60 IOs, all 3.3v
> >> 30MHz clock
> >> Logic equivalent to around 100 CPLD macrocells
> >> Free or low cost (<$500) design software
>
> >> The Xilinx S3A/AN-50 is the cheapest I've found so far, but is a a bitover-specced.
> >> CPLDs seem to get expensive above 72 cells and don't tend to have RAM
>
> >the IC you need is always the one that doesnt exist
>
> >S3-50AN prices do go below 4$ but not at 100x qty.
> >in 100x qty, it proabably more than your target price 7.5 (depend how
> >good you deal..)
>
> >Xilinx disties say: leadtime 12 weeks, call for order
> >Digikey has 4 pcs in stock
>
> >if you can deal with 2 KB RAM, then lattice EC1 is 6.1$ online price
> >available in stock, need spi flash, but it still cheap total price
>
> >but here XC3S50A would be better at about same price
>
> >Lattice XP3 is too expensive with online pricing.. $10, stock YES,
> >this is the IC that needs NO Externals, no flash, no LDO, just 3.3V !
>
> >Actel A3P060, is cheap, but again 2K RAM only
>
> >all the above have free tools
> >Altera doesnt seem to have devices that come to your desired price
> >range
>
> >hm.. call lattice disti, say you would like XP3-VQ100, but your BOM
> >limit is 7.5$ see what they say !!
>
> >if price doesnt come down, place xc3s50a-vq100 order on digikey, to
> >secure your devices before those are gone too (disties have no stock.
> >leadt=12w)
>
> >Antti
>
> Thanks for the suggestions - the Lattice EC1 looks a pretty good fit on all counts - RAM is 'only
> just' enough, but means I'm not paying for stuff I don't need.
>
> I even found a cheap eval board for it :http://www.msc-toolguide.com/lattice...ion-board.html

I had to do this same search last year and I found very little that
would suit my needs... in fact, I found exactly one part that really
was suited to the job. The problem you will find with most parts is
not actually the price of the part itself, but rather the price of the
package. The FPGA vendors will attest to the fact that the pricing of
these parts at the low end is mostly governed by testing which is in
tern dominated by the cost of testing the I/Os. So the lower the pin
count, the cheaper the part.

I also has space constraints which in the end led me to the Lattice XP
in the 100 pin QFP package. It is about $10 (or maybe a squeak less)
at qty 100 and was the only comparable part in this price range.
Remember that the XP has internal Flash and the ram parts do not. I
remember that some ram based FPGA vendors would jump up and down and
insist that ram was the only way to go when considering the advantages
of die size and how it would impact the cost. I guess that really is
not the whole picture is it?

I am using the LFXP3C-3TN100C which is 3.3 volt only power with 63 or
64 I/Os, IIRC, commercial temp and the slowest speed grade. If you
sweet talk you local disti or Lattice rep, I bet you can get them for
$9. I am actually using contract turnkey assembly, so I don't know
exactly what they are paying, but my local guy has quoted me $9.50 for
preprogrammed parts.

The only issue may be availability, but then I have never found *any*
FPGA that they maintain significant amounts of stock at all times.
Mouser sells Lattice, but the inventory is mostly at Lattice and is
drop shipped.

I did not find one other part that was better in any regard and I
don't recall finding any others that met all these constraints... but
then it was a year ago...

Rick