How do you design these days?
in [Design]
|
From: Joel Koltner on 4 Jan 2010 14:04 > On Sun, 03 Jan 2010 10:19:37 -0800, John Larkin >>One mistake we used to make too often was swapping V+ and V- on >>opamps. Engineers tend to flip an opamp to make the feedback path look >>nice (different for inverting/noninverting) and that moves the power >>pins too. We check that really hard now. We've been bitten by that. Originally some of the op-amps didn't even have their power pins labeled -- the idea was "Vcc is on the top, Vee is on the bottom" -- which of course is almost guaranteed to create an error if someone flips a symbols. So now we require that all pins are labeled... I like Keith's idea of adding an alternative view so that power pins can always end up with Vcc on top and Vee on the bottom. It's always been a battle with the techs to get them to add more than one view of a part -- they were really annoyed when I asked for about a half-dozen views for the "universal" logic gate ICs (NC7SZ57 and NC7SZ58). Some tools make this sort of thing easier than others... ORCAD, for instance, has the notion that a "part" can have only two views (they were thinking "normal" and DeMorgan) and exactly one footprint. Pulsonix is far more powerful in that if keeps symbols, footprints, and parts all in separate libraries and you can have a part consist of as many different symbols and footprints as you feel like. I seem to recall that PADS is somewhere inbetween those two extremes... (Obviously with any tools you can just create multiple parts to work around such restrictions, but then if you discover an error in one you have to make sure you correct all of the "equivalent" parts.) ---Joel
From: Joerg on 4 Jan 2010 14:53 krw wrote: > On Sat, 02 Jan 2010 20:45:11 -0700, Jim Thompson > <To-Email-Use-The-Envelope-Icon(a)My-Web-Site.com/Snicker> wrote: > >> On Sat, 02 Jan 2010 21:36:09 -0600, krw <krw(a)att.bizzzzzzzzzzz> wrote: >> >>> On Sat, 02 Jan 2010 17:03:43 -0800, John Larkin >>> <jjlarkin(a)highNOTlandTHIStechnologyPART.com> wrote: >>> >>>> On Thu, 31 Dec 2009 09:41:54 -0800, "Joel Koltner" >>>> <zapwireDASHgroups(a)yahoo.com> wrote: >>>> >>>>> "John Larkin" <jjlarkin(a)highNOTlandTHIStechnologyPART.com> wrote in message >>>>> news:7glpj5l1a7i5nm45bsp5gfhc016e3kjgo8(a)4ax.com... >>>>>> On Thu, 31 Dec 2009 09:10:22 -0700, Don Lancaster <don(a)tinaja.com> >>>>>>> It is NEVER right the first time. >>>>>> We sell about 80% of our rev A boards, with no prototypes. Assuming >>>>>> the first unit won't work is self-fulfilling, and a good way to make >>>>>> sure the third iteration won't work either. >>>>> I agree with your philosophy John... but you do allow yourself a non-zero >>>>> number of blue wires or a couple of tack-soldered components or something on >>>>> those saleable rev. A boards too though, right? >>>> Sure, that happens. But it's supposed to be embarassing. >>>> >>>> We make blue boards and I think we should use red wires. But >>>> production insists on blue. >>> I know one company that does use red wires, so oops's stand out like >>> the sore thumb they are. >> Isn't "blue wire" sort of a historic standard ?:-) > > In IBM they were known as "yellow wires", not matter what color. The > original Teflon WireWrap wires were yellow and the name was kept. I > don't even remember what color we use now. I still use yellow wires. Age is showing ... -- Regards, Joerg http://www.analogconsultants.com/ "gmail" domain blocked because of excessive spam. Use another domain or send PM.
From: markp on 4 Jan 2010 16:48 "Joel Koltner" <zapwireDASHgroups(a)yahoo.com> wrote in message news:gZq0n.5895$5n7.5104(a)en-nntp-09.dc1.easynews.com... >> On Sun, 03 Jan 2010 10:19:37 -0800, John Larkin >>>One mistake we used to make too often was swapping V+ and V- on >>>opamps. Engineers tend to flip an opamp to make the feedback path look >>>nice (different for inverting/noninverting) and that moves the power >>>pins too. We check that really hard now. > > We've been bitten by that. Originally some of the op-amps didn't even > have their power pins labeled -- the idea was "Vcc is on the top, Vee is > on the bottom" -- which of course is almost guaranteed to create an error > if someone flips a symbols. So now we require that all pins are > labeled... > > I like Keith's idea of adding an alternative view so that power pins can > always end up with Vcc on top and Vee on the bottom. It's always been a > battle with the techs to get them to add more than one view of a part -- > they were really annoyed when I asked for about a half-dozen views for the > "universal" logic gate ICs (NC7SZ57 and NC7SZ58). > > Some tools make this sort of thing easier than others... ORCAD, for > instance, has the notion that a "part" can have only two views (they were > thinking "normal" and DeMorgan) and exactly one footprint. Pulsonix is > far more powerful in that if keeps symbols, footprints, and parts all in > separate libraries and you can have a part consist of as many different > symbols and footprints as you feel like. I seem to recall that PADS is > somewhere inbetween those two extremes... (Obviously with any tools you > can just create multiple parts to work around such restrictions, but then > if you discover an error in one you have to make sure you correct all of > the "equivalent" parts.) > > ---Joel > I have used Orcad Capture quite extensively, it actually has the concept of multi-part schematic symbols. There are two options, heterogenous or homogenous parts (i.e. different part symbols, or the same part symbol for all parts). If you define a 4 gate opamp as heterogenous with 5 parts you can create the 4 opamp gates with their repective pin numbers for each, and a fifth part with just the power supply pins only. That way you can flip or rotate the individual gates without affecting the power supply part. This is really useful with things like large FPGAs and bridge chips for example, and of course any multi-gate device such as opamps or some of those multi-gate CMOS devices. A minor bug-bear I have though is that if you forget to put the power supply part on the schematic it won't flag it up as having unconnected power pins in the DRC (at least in the older versions of Capture). Mark.
From: Joel Koltner on 4 Jan 2010 18:02 Hi Mark, "markp" <map.nospam(a)f2s.com> wrote in message news:7qf5u7Fk7nU1(a)mid.individual.net... > I have used Orcad Capture quite extensively, it actually has the concept of > multi-part schematic symbols. There are two options, heterogenous or > homogenous parts (i.e. different part symbols, or the same part symbol for > all parts). If you define a 4 gate opamp as heterogenous with 5 parts you > can create the 4 opamp gates with their repective pin numbers for each, and > a fifth part with just the power supply pins only. That way you can flip or > rotate the individual gates without affecting the power supply part. Agreed, that is useful, and I do the same thing for, e.g., quad or hex logic gates (...also prompting whining from some people who haven't seen this done previously). For dual op-amps, I think to date I usually just add the power pins to both of them (and the DRC function tells me if I didn't connect them both the same way), but even there I can understand someone splitting off a separate power block, and it makes lots of sense for a quad op-amp. The nice thing about CAD packages that let you have as many symbols as you want for a given part is that you don't have to debate these things with your fellow engineers or techs -- I want a quad op-amp symbol that shows all four op-amps together and 2 power pins, I can have it. You want 4 separate symbols plus a little power block, you can have it. Yet we're both still linked to the same footprint, the same manufacturer's part no., etc. (A more concrete example of this that I use is bussed resistor packages -- sometimes I'd like all 4 or 8 or however many of them displayed as one symbol right next to each other, other times I'd like all discrete symbols.) > A minor bug-bear I have though is that if you forget to put the power supply > part on the schematic it won't flag it up as having unconnected power pins > in the DRC (at least in the older versions of Capture). I make the power block the first "gate," so it shows up immediately when you go to place the part. Hence it requires additional effort to forget about it. :-) ---Joel
From: Joerg on 4 Jan 2010 19:03
markp wrote: > "Joel Koltner" <zapwireDASHgroups(a)yahoo.com> wrote in message > news:gZq0n.5895$5n7.5104(a)en-nntp-09.dc1.easynews.com... >>> On Sun, 03 Jan 2010 10:19:37 -0800, John Larkin >>>> One mistake we used to make too often was swapping V+ and V- on >>>> opamps. Engineers tend to flip an opamp to make the feedback path look >>>> nice (different for inverting/noninverting) and that moves the power >>>> pins too. We check that really hard now. >> We've been bitten by that. Originally some of the op-amps didn't even >> have their power pins labeled -- the idea was "Vcc is on the top, Vee is >> on the bottom" -- which of course is almost guaranteed to create an error >> if someone flips a symbols. So now we require that all pins are >> labeled... >> >> I like Keith's idea of adding an alternative view so that power pins can >> always end up with Vcc on top and Vee on the bottom. It's always been a >> battle with the techs to get them to add more than one view of a part -- >> they were really annoyed when I asked for about a half-dozen views for the >> "universal" logic gate ICs (NC7SZ57 and NC7SZ58). >> >> Some tools make this sort of thing easier than others... ORCAD, for >> instance, has the notion that a "part" can have only two views (they were >> thinking "normal" and DeMorgan) and exactly one footprint. Pulsonix is >> far more powerful in that if keeps symbols, footprints, and parts all in >> separate libraries and you can have a part consist of as many different >> symbols and footprints as you feel like. I seem to recall that PADS is >> somewhere inbetween those two extremes... (Obviously with any tools you >> can just create multiple parts to work around such restrictions, but then >> if you discover an error in one you have to make sure you correct all of >> the "equivalent" parts.) >> >> ---Joel >> > > I have used Orcad Capture quite extensively, it actually has the concept of > multi-part schematic symbols. There are two options, heterogenous or > homogenous parts (i.e. different part symbols, or the same part symbol for > all parts). If you define a 4 gate opamp as heterogenous with 5 parts you > can create the 4 opamp gates with their repective pin numbers for each, and > a fifth part with just the power supply pins only. That way you can flip or > rotate the individual gates without affecting the power supply part. This is > really useful with things like large FPGAs and bridge chips for example, and > of course any multi-gate device such as opamps or some of those multi-gate > CMOS devices. A minor bug-bear I have though is that if you forget to put > the power supply part on the schematic it won't flag it up as having > unconnected power pins in the DRC (at least in the older versions of > Capture). > That's how Eagle does it. You have four parts in a quad opamp. When you want to connect power to dedicated supplies other than, say, VSS and VEE or you want it to show for clarity you click "Invoke". That pops up the fifth part which is the power pins. -- Regards, Joerg http://www.analogconsultants.com/ "gmail" domain blocked because of excessive spam. Use another domain or send PM. |