On May 13, 6:31*pm, Mike Harrison <m...@whitewing.co.uk> wrote:
> On Wed, 13 May 2009 12:36:26 -0700 (PDT), rickman <gnu...@gmail.com> wrote:
> >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 all the 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 (<$500) design software
>
> >> >> The Xilinx S3A/AN-50 is the cheapest I've found so far, but is a a bit over-specced.
> >> >> CPLDs seem to get expensive above 72 cells and don't tend to have RAM
>
> >> >the IC you need is always the one that doesnt exist
>
> >> >S3-50AN prices do go below 4$ 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.
>
> And nobody seems to do low pin-count FPGAs, and CPLDs seem to have a big price jump above 72
> macrocells which I've never quite understood - there appears to be a gaping hole between the $2 CPLD
> and the $8ish FPGA.

I used a 256 cell CPLD in a project once and yes, it was a bit
pricey. I think the routing of these parts goes up very quickly as
the size increases. They don't have the same routing structure as an
FPGA and that may be what drives up the cost and limits the size.


> > *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?
>
> Well the pricing of S3A+SPI flash compared to S3AN seems to support this....
> Single-chip and single-supply are nice, but not if the additional cost isseveral times that of
> external regulator/flash!

What pricing do you have for these parts? I'm not clear on which are
saying is the expensive option. Both of the Spartan devices use two
die, one for the FPGA and one for the flash. The S3AN parts just put
them both in the same package. That is how they did it when they came
out; I don't think they have changed this. According to Xlinx Flash
is just not compatible with their small geometry process.


> >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.
>
> Farnell also list several Lattice devices, so availability appears to at least be better than
> Xilinx.

Xilinx should be as available as the others, no?

Rick