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From: Nico Coesel on 20 Apr 2008 04:21 Joerg <notthisjoergsch(a)removethispacbell.net> wrote: >Nico Coesel wrote: >> Dave <dhschetz(a)gmail.com> wrote: >> >>> Does anybody out there have a good methodology for determining your >>> optimal FPGA pinouts, for making PCB layouts nice, pretty, and clean? >>> The brute force method is fairly maddening. I'd be curious to hear if >>> anybody has any 'tricks of the trade' here. >> >> I start thinking about how the PCB should be routed the minute I start >> to draw a schematic. I always draw components with their actual >> pin-outs. This helps to group pins together and it helps to >> troubleshoot the circuit when the prototype is on your bench (no need >> to lookup the pinouts because they are in your diagram). >> > >For quad opamps like the LM324 as well? No. Those (and simple logic) have very few pins. -- Programmeren in Almere? E-mail naar nico(a)nctdevpuntnl (punt=.)
From: Joerg on 20 Apr 2008 16:22 Nico Coesel wrote: > Joerg <notthisjoergsch(a)removethispacbell.net> wrote: > >> Nico Coesel wrote: >>> Dave <dhschetz(a)gmail.com> wrote: >>> >>>> Does anybody out there have a good methodology for determining your >>>> optimal FPGA pinouts, for making PCB layouts nice, pretty, and clean? >>>> The brute force method is fairly maddening. I'd be curious to hear if >>>> anybody has any 'tricks of the trade' here. >>> I start thinking about how the PCB should be routed the minute I start >>> to draw a schematic. I always draw components with their actual >>> pin-outs. This helps to group pins together and it helps to >>> troubleshoot the circuit when the prototype is on your bench (no need >>> to lookup the pinouts because they are in your diagram). >>> >> For quad opamps like the LM324 as well? > > No. Those (and simple logic) have very few pins. > Ok, then you'd have to modify your statement "always" :-) Am I the nitpicker or what? -- Regards, Joerg http://www.analogconsultants.com/ "gmail" domain blocked because of excessive spam. Use another domain or send PM.
From: John Larkin on 20 Apr 2008 16:47 On Sat, 19 Apr 2008 14:17:44 -0700, Joerg <notthisjoergsch(a)removethispacbell.net> wrote: >Nico Coesel wrote: >> Dave <dhschetz(a)gmail.com> wrote: >> >>> Does anybody out there have a good methodology for determining your >>> optimal FPGA pinouts, for making PCB layouts nice, pretty, and clean? >>> The brute force method is fairly maddening. I'd be curious to hear if >>> anybody has any 'tricks of the trade' here. >> >> I start thinking about how the PCB should be routed the minute I start >> to draw a schematic. I always draw components with their actual >> pin-outs. This helps to group pins together and it helps to >> troubleshoot the circuit when the prototype is on your bench (no need >> to lookup the pinouts because they are in your diagram). >> > >For quad opamps like the LM324 as well? That can make a schematic harder >to read and will also cause a nightmare if the layouter wants to swap >amp A with amp C and stuff like that. > >[...] A quad opamp doesn't have 1738 pins! John
From: Joerg on 20 Apr 2008 17:13 John Larkin wrote: > On Sat, 19 Apr 2008 14:17:44 -0700, Joerg > <notthisjoergsch(a)removethispacbell.net> wrote: > >> Nico Coesel wrote: >>> Dave <dhschetz(a)gmail.com> wrote: >>> >>>> Does anybody out there have a good methodology for determining your >>>> optimal FPGA pinouts, for making PCB layouts nice, pretty, and clean? >>>> The brute force method is fairly maddening. I'd be curious to hear if >>>> anybody has any 'tricks of the trade' here. >>> I start thinking about how the PCB should be routed the minute I start >>> to draw a schematic. I always draw components with their actual >>> pin-outs. This helps to group pins together and it helps to >>> troubleshoot the circuit when the prototype is on your bench (no need >>> to lookup the pinouts because they are in your diagram). >>> >> For quad opamps like the LM324 as well? That can make a schematic harder >> to read and will also cause a nightmare if the layouter wants to swap >> amp A with amp C and stuff like that. >> >> [...] > > A quad opamp doesn't have 1738 pins! > Well, yes, I was just wondering about whether Nico really always draws the physical package. Looks like he doesn't for smaller stuff. With 1738 pins you can only hope that the FPGA has enough routing resources. That used to be a major pain in the early 90's. Don't know about nowadays since other guys design the parts with the big FPGAs. And I am glad I don't have to deal with BGA, at least not with large ones ... -- Regards, Joerg http://www.analogconsultants.com/ "gmail" domain blocked because of excessive spam. Use another domain or send PM.
From: John Larkin on 20 Apr 2008 17:56
On Sun, 20 Apr 2008 14:13:21 -0700, Joerg <notthisjoergsch(a)removethispacbell.net> wrote: >John Larkin wrote: >> On Sat, 19 Apr 2008 14:17:44 -0700, Joerg >> <notthisjoergsch(a)removethispacbell.net> wrote: >> >>> Nico Coesel wrote: >>>> Dave <dhschetz(a)gmail.com> wrote: >>>> >>>>> Does anybody out there have a good methodology for determining your >>>>> optimal FPGA pinouts, for making PCB layouts nice, pretty, and clean? >>>>> The brute force method is fairly maddening. I'd be curious to hear if >>>>> anybody has any 'tricks of the trade' here. >>>> I start thinking about how the PCB should be routed the minute I start >>>> to draw a schematic. I always draw components with their actual >>>> pin-outs. This helps to group pins together and it helps to >>>> troubleshoot the circuit when the prototype is on your bench (no need >>>> to lookup the pinouts because they are in your diagram). >>>> >>> For quad opamps like the LM324 as well? That can make a schematic harder >>> to read and will also cause a nightmare if the layouter wants to swap >>> amp A with amp C and stuff like that. >>> >>> [...] >> >> A quad opamp doesn't have 1738 pins! >> > >Well, yes, I was just wondering about whether Nico really always draws >the physical package. Looks like he doesn't for smaller stuff. > >With 1738 pins you can only hope that the FPGA has enough routing >resources. That used to be a major pain in the early 90's. Don't know >about nowadays since other guys design the parts with the big FPGAs. And >I am glad I don't have to deal with BGA, at least not with large ones ... The biggest ones we use are Sparten 3's with 456 balls on 1 mm centers. We haven't had any routing problems so far, doing pretty complex stuff at 128 MHz clock rates. Our in-house BGA soldering yield, to date, is exactly 100%. BGAs seem to be a lot easier to solder reliably than fine-pitch leaded parts. Easier to inspect, too, since you can't inspect them at all. John |