EEVblog Electronics Community Forum
General => General Technical Chat => Topic started by: ticktock3t on February 22, 2013, 09:02:58 am
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I always thought FPGAs were for prototyping purposes only. In some of Dave's Rigol teardowns he always points out at least one FPGA. Is this done to keep costs down?
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ASIC masks are way expensive and changes require new masks = more cost. FPGAs make changes easy peasy and are available off the shelf at the cost of performance and higher per-unit costs but no huge up-front costs.
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No, FPGAs is not only for prototyping. I bet there is an FPGA on every device like laptops, TVs, printers etc.
Alexander.
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No, FPGAs is not only for prototyping. I bet there is an FPGA on every device like laptops, TVs, printers etc.
Alexander.
Highly unlikely.
FPGAs are only economical for products made in volumes too low to justify the 1-off costs of an ASIC, or which need the flexibility to customise or update the functionality. They will always have less efficient usage of silicon than an ASIC.
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midrange to highend LCD/DLP data projectors often have a FPGA because of the huge amount of data at 1080P which needs to be processed and adjusted in realtime (keystone, dynamic gamma etc).
It's far safer for them to use a FPGA as bugs can be fixed without hardware changes and projectors are expensive devices anyway so a FPGA doesn't do much to the unit cost.
According to the service manual my Panasonic AE900 has a FPGA for "Dynamic Gamma, Iris control and lamp control"
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They use FPGA's for possibly two reasons:
1) because it's maybe the only way to get the high performance for the overall system cost they are targeting.
Even the fastest processors are no good for modern real-time DSO sampling architectures, so that only leaves an FPGA, or to spin your own ASIC.
Yes, FPGA'S are expensive devices, but the NRE cost is zero.
Ballpark calcs:
I don't know how many units they be targeting, but lets say it's 100K units.
An ASIC might cost you say $1M. So that's $10 per unit just for the NRE alone, not including the actual chip.
The Xilinx XC6SLX25 used in the DS2000 for example is $55 one-off. Not sure what it is for 100K units, but lets say $10. So similar price to the ASIC when you include the chip cost, testing, etc. Then you can't use the same part again in the design for something else (The DS2000 has 3 FPGA's)
And then there is the benefit of being able to update the thing in-system, if you find a bug, or some competitor comes out with a new feature that you want to match. That alone is enough reason to pay more for an FPGA (if it is actually more expensive).
Dave.
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FPGA's are sometimes used in products because they allow reconfig on-the-fly, I know of one USB scope company that do this (or certainly used to).
For example, you could do SPI serial decoder triggering in part of the FPGA, then change to I2C triggering by reloading the FPGA. If you have lots of different trigger-modes, then you reuse the silicon. You could have a custom ASIC that does it all, but perhaps the skill-sets, lead-times, NRE's, volumes are against you.