What is the difference between ASIC and FPGA?.

Hello, I have two questions about Electronic circuit board design. These are the questions:

1st question: What is the main difference between FPGA and ASIC, recently I went to some exhibition, there I heard from somebody, he says "we are designing a prototype handset based on FPGA, which was used between DSP chip and main processor, later on we will go wityh ASIC", I didn't understand quite well, what was the main difference, also whereever FPGA was used, can that be replaced by ASIC?.

2nd question: What are the main stepps involved in circuit board design?. Suppose if I want some board to be designed, what are the steps I have to do (like a fabless design), how can I contact the fab to get my prottype board as well as production baord?.

Thanks in advance, appreciated.

Reply to
tvnaidu
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An FPGA is a Field Programmable Logic array. As the name implies, it can be programmed to be anything within its capability. ASIC stands for Application Specific IC. In his context, he means a custom IC. So, the FPGA is a prototype for the final version. You don't make one ASIC, you make tens/hundreds of thousands.

Tam

Reply to
Tam/WB2TT

Minor correction: An FPGA is a Field Programmable Gate Array. ^ ^^^^

Reply to
Guy Macon

Field Programable Gate Array: a bunch of logic cells that you can program to do lots of different things. One of these things would may be the thing you want done.

Application Specific Integrated Circuit: a chip designed to do a certain job or a small group of jobs. If you want to do something else get a different chip.

Basically it like this:

You can make the prototype with very costly general purpose FPGAs, some DSPs, and have a cable running off to a big battery. This version costs a billion dollars each. Our target cost is 3 dollars so we will have to spend 10 Million on making a custom chip and sell about 4 million units to make it pay.

1) Decide what the bourd should do. 2) Make a schematic that does that. 3) Decide the mounting issues. 4) Select the component packages. 5) Buy board layout software if you intend to do it yourself 6) Start placing the parts 7) Discover that they won't fit and loop back to 3 8) Finish placing 9) Start running the traces 10) Discover that you can't route as placed and loop back to 8 11) Finish routing 11) Check the proposed layout 12) Rip out large sections and loop back to 8 13) Check the improved version 14) Check it again 15) Make Gerber plots and an NC drill file 16) Check the Gerbers and drill file 17) Compose a README.TXT 18) Zip together the Gerber, NC drill and README.TXT 19) Get bids on making the board 20) Select a vendor and send off the files 21) Get a phone call from the vendor pointing out an error 22) Loop back to 11 and increase the ring on the vias etc 23) Get the boards from the FAB house. 24) Gather the parts needed 25) Discover that you can't get the MOSFET in a DPAK loop back to 4 26) Stuff the board 27) Apply power 28) Scrape the burning parts off your face 29) Replace the burned parts 30) Apply the right power the right way around this time 31) Begin debugging the board 32) Discover the errors that are not just part values 33) Loop back to 1 34) Prepair BOMs etc for the production build. 35) Fight off the accounting guy who wants to lower cost. 36) Make the pre-pre-production units 37) Correct the BOM and assembly drawings 38) Start testing the pre-pre-production units 39) Build the pre-production units 40) Do major testing 41) Discover that the specifications from marketing have changed 42) Loop back to 1
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kensmith@rahul.net   forging knowledge
Reply to
Ken Smith

Development / debugging: An FPGA can be re-programmed again and again, until you get it right. An ASIC is hard-wired with a mask - you can't change it once it's fabricated!

Power: An FPGA consumes more power than an ASIC.

Cost per unit: ASICs are only made in large quantities - the total investment is large - but the unit cost is small. FPGAs can be used for one-offs, but would not be competitive in large voilumes.

Reply to
Andrew Holme

This is good! We should put this in a F.A.Q. ;)

-- "Welcome to the new millennium, where ingenuity is dead and SpongeBob Squarepants rules the world..." MCJ 200406

Reply to
Mark Jones

[snip]

The first step should be a specification for the finished design. This might include mechanical specifications as well as functional and power consumption specifications. If UL and FCC (or similar) approvals are required, that should be part of the specification, too.

Then I guess schematic capture would be the next step. Schematic capture just means drawing the schematic with appropriate software. Around this time you want to start making sure that you can get all the parts you are using.

The next step would be layout. To do this, you have to decide how many layers the board will be, where the parts will go on the board, where you want to put fills and floods and so on. Any nets requiring special treatment might best be done first. At this stage you want to have samples of the parts on hand so you can compare the physical part with the layout you are doing.

When layout is finished, you need to prepare the fabrication files and send them off to the board house. They can then give you a quote for what the raw boards will cost. Around this time you want to have all your parts in stock in quantities sufficient for the number of boards you will build.

Once the boards come back, someone will need to solder all the parts to the board, and do any required mechanical assembly. Sometimes the raw boards are tested, either by the fabricator or by you.

If you have limited personnel, you can contract out some or even all of the design. Or you could write the specification, draw the schematic, and write layout guidelines, then contract out the rest of the design and fabrication. But layout can be absolutely critical for some designs, so be careful!

In general, if the design involves one or more of the following, layout might be critical: small analog (or RF) signals; fast digital signals; high voltage, power or current.

I should re-iterate that if the finished product requires agency approvals (FCC, UL, etc.) then you will need to take that into account from the beginning.

--Mac

Reply to
Mac

snipped-for-privacy@green.rahul.net (Ken Smith) wrote in news:cscid6$76e$ snipped-for-privacy@blue.rahul.net:

Here's a good tutorial about designing PCBs (minus all the real-world details given in the list above):

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Dave Van den Bout
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Reply to
Dave Vanden Bout

Great Idea!

Where's the FAQ?

Thanks, Rich

Reply to
Rich Grise

board design")

Done:

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=================== Philip Freidin snipped-for-privacy@fpga-faq.com Host for

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Reply to
Philip Freidin

The FPGA FAQ is at:

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=================== Philip Freidin snipped-for-privacy@fpga-faq.com Host for

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Reply to
Philip Freidin

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