EE's who do PCB Layout

Joel Kolstad wrote:


True. But being there on a regular basis can be a bit tough if the client is on the other side of the Klondike river ;-)

If it doesn't have to be right now. Did you guys consider using the receive section in chips like this one?
http://focus.ti.com/lit/ds/symlink/cc1000.pdf
20mW will be a challenge at 900MHz though, even with this chip. Would auto-polling be possible in your application or is it pretty much a continuous data stream? What can also help is to transmit the data in chunks at a much higher rate and send the receiver to sleep during breaks.
--
Regards, Joerg

http://www.analogconsultants.com
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No, it's not right now... just starting to think about an upcoming project which appears to be about 90% of a sure-thing at this point.

I haven't looked at that one before; thanks for the link. (Some of the low-power parts that we've used in the past were aimed at, e.g., paging applications and unfortunately are now gone.)

It sleeps for awhile, wakes up to listen every now and again, and repeats. (It initially has to listen for awhile to "sync up" and then, knowing it's own ID, can figure out when to sleep and when to listen.)
---Joel
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Joel Kolstad wrote:

Good. Many of the calls I get are like "Well, the roof is already on fire...".

Yes, pagers are almost gone except for emergency crews. Even if the chips weren't gone I would not bank on them for anything that needs to remain in production for years. And from experience I'd try to stick to mainstream manufacturers and be careful with recently sold or acquired companies or product lines. Sometimes those parts can do a quick Houdini.
Take a look at chips for higher-end keyless entry systems. Meaning the ones that really work, not the super-cheap super-regen receivers.

If your 20mW spec is for the average consumption that should be no problem. If it is for the active phase it'll present a bit of a challenge at 900MHz. But I guess challenges are why guys like us chose engineering.
--
Regards, Joerg

http://www.analogconsultants.com
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On Sun, 5 Aug 2007 16:44:07 -0700, "Joel Kolstad"

Fairchild NC7SV74. US8 package, single D-flop, 1 ns typical prop delay at 3.3 volts. 10K ECL wasn't that fast.
Works down to 0.9 volts, but a bit slower.
John
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Nice.
Something like 4-5 years ago when TinyLogic started to become popular, I lamented that -- at the time -- they were missing a single-bit 'flop and a single-bit tri-state buffer. I was happy to see when I looked some months ago now that both are available... and I've since used them as well!
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I do my own when our layout guy is either swamped or I'm convinced that the layout is critical enough that once you sum up the total time it'll take him plus my own time, it's significantly longer than if I just did it myself.
The process you describe -- someone other than the EE does the layout, the EE checks the results, iterations occur as necessary -- is pretty standard in most companies, especially those of significant size. You're right to notice some of the inherent inefficiencies in this process, but this has to be balanced with the fact that multiple bodies working on the same problem generally will finish in noticeably less time than one working alone (although certainly not in 50% of the time for anything much more complex than, e.g., breaking rocks :-) ) and also -- from the financial point of view -- the EEs generally cost a company more than the layout guys.
Hence my personal "policy" above of letting the layout guy do it when "reasonable" -- obviously a subjective call. This is largely influenced by how good your PCB guy is, and how well you communicate with them. While Joerg seems to have found himself a really good layout person, my experience hasn't been as good and most of the guys I've worked with had relatively little understanding of how, e.g., high-frequency analog or RF "works" (most of them generally had two-year degrees, although these days I very much doubt that most BSEEs fresh out of college are any better).
You'll probably have a better shot at convincing your boss to let you do your own PCBs if you're working on analog, RF, or switching power supply designs -- with those designs it's a lot easier to demonstrate that layout is much more critical than some "generic" digital board (e.g., microcontrollers) where even really sloppy layout still tends to work.
I spent a summer working as an intern at a Big Company (hundreds of millions per year revenue, thousands of employees) that had an entire layout *department*, and unfortunately their "process" was so heavily oriented towards high-volume (often overseas) manufacturing -- implying lots of documentation, many reviews, etc. -- that for prototyping purposes the engineering department I was with simply used freebie software from, e.g., ExpressPCB! This was *much* faster AND cheaper (since the cost of layout was still charged backed to engineering, of course) than going through the layout department, but also quite sad that the company had become so segmented and political that the EEs just wanting to build a stupid prototype weren't "allowed" to use the fancy software the layout department had (the question of course being then how the software licenses would be paid for...).
---Joel
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You were lucky you were allowed to. A similar sized notionally high quality oriented company I spent some time in didn't do prototypes, having spent tens of thousands per seat on Cadence design software engineers were supposed to simulate their designs avoiding the need for prototypes.
The layout process was as a (notional) quality enforcement mechanism. No layout would be started without around 16 signatures on a check list. Project manager, quality control, component engineer, CAD library engineer, drawing standards engineer, PCB layout engineer, reliability engineer, thermal engineer, environmental engineer, safety engineer, EMC engineer and more I don't remember. When you need signatures from 16 people at least one is bound to be on holiday or off site for a fortnight. Even when you got everything right no PCB would ever start layout without a 2 week delay.
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It was a little bit of a skunkworks projects -- hence the reason they were using free software rather than one of the inexpensive options.
I've spent a lot of time trying to make it clear to managers (those without "hard" engineering backgrounds) that there's a *huge* difference between the software, hardware, and procedures needed for *prototypes* vs. that for *production* and that while there may be some correlation between how much you spend on a simulator and how many prototypes you need to build, there's an even bigger correlatoin with who you hire to get the job down. :-) I'm heartened that those around here who appear to be quite good at circuit design -- folks like Joerg and John Larkin -- still seem to do plenty of measurements on prototypes and don't expect that a fancy simulator is going to eliminate the need for them entirely. (There are folks like Jim Thompson here who probably has plenty of "1st cut" design successes, but he gets fab models for transistors pre-simulation and then probably extracted netlists with parasitics included prior to fab -- something of a "leg up" there!")
---Joel
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Don't ask - *do* ;-)
Most decent engineers I have been around *scorn* the formal process for prototype work because it totally breaks the flow to wait for weeks and weeks for desicions to be made by the mis-informed - and the boss usually will not care if you can sneak whatever-it-is-you-need onto a small value order (or the credit card - like most evaluation boards and development systems these days; Microchip really broke the mold with the PIC development system at USD 80,--).
As long as you get results you will get away with it.
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I just run the whole thing.
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