On Wed, 13 May 2009 12:36:26 -0700 (PDT), rickman <[email protected]> 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 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 is several times that of
external regulator/flash!


>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.