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?.
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.
>An FPGA is a Field Programmable Logic array.
Minor correction: An FPGA is a Field Programmable Gate Array.
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
>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?.
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.
>What are the main stepps involved in circuit board design?.
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
kens...@rahul.net forging knowledge
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
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
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
> Hello, I have two questions about Electronic circuit board design.
> These are the questions:
> 1st question:
> 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?.
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
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.
> Thanks in advance, appreciated.
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
Here's a good tutorial about designing PCBs (minus all the real-world
details given in the list above):
<snipped THREE PAGES of THRICE-QUOTED crap>
> This is good! We should put this in a F.A.Q. ;)
Where's the FAQ?
The FPGA FAQ is at: http://www.fpga-faq.com