The problem with using a uP in such projects is if you are designing a chip, you need to know how to do it with gates as often that is the smallest and lowest power solution. The ability to hand craft logic is disappearing rapidly, but is very much needed in mixed mode chips which are not done on fine geometry processes.
snipped-for-privacy@sushi.com snipped-for-privacy@sushi.com posted to sci.electronics.design:
OK. I know this might sound a bit weird but, it seems that mixed mode in not chasing minimum geometry devices like digital is. I can see some reasons for this, but some of the issues can be reduced by some thoughtful scale reduction. Is the issue that the tools cannot keep up?
Sub 0.18u devices leak like sieves... not very conducive to quality analog work.
No. Models is models is models....
...Jim Thompson
What's the reason that you can't make, say, 10u or 2u devices on a
0.18u process?Best regards, Spehro Pefhany
There's the wirebond issue, too. Lots of chips are size-limited by the i/o connections, so there's no point in making the devices smaller. A billion dram bits on a chip is good, but a million opamps doesn't make sense.
John
You can, except the 0.18u feature-size VERTICAL dimension is still there, plus the doping levels are still the same as well.
HOWEVER, I work regularly on mixed device processes. The current project has multiple diffusions and implants, so I have 3V, 2V and
1.25V devices available....Jim Thompson
If that A-Fib isn't treatable in a classic way check this out:
Unfortunately they went with a bit too much flashplayer glitz so I cannot see the site well. If you ever take that route rest asssured that the patient iso has been designed by yours truly :-)
-- Regards, Joerg http://www.analogconsultants.com
Finer geometry means lower voltage. This can impact dynamic range. The gain is lower due to higher gds and onset of impact ionization. This is somewhat offset by higher gm, but the net effect is less gain. Matching is better with finer geometry, and VT0 is better controlled due to less influence by qss.
Mine was. Just a jump start, after six weeks on Coumadin, two of which I was also on Lovenox (*expensive*).
Interesting. They talked about ablation (not for me) and a friend had it done. I was never clear why/how it worked. That site explained it rather simply.
I'm hoping I don't have to go through that again. What a pain, daytime TV sucks, and not cheap either.
From what JohnL has said, he likely did the guts of the MRI machine I was inspecting the innards of, too. Good company here! ;-)
-- Keith
No, I only do the gradient drivers for small-bore stuff, like 4" and
8" machines for imaging lab animals, and even smaller micro-imaging systems. Those can be dinky but fast high-precision, 100 amp, 170-volt (17 KW per axis!) drivers. The full-body stuff is much higher power, always switchers (Copley is pretty good) and slower and a lot noisier.I had my head MRI'd earlier this year (spare me the predictable witticisms, guys) and it was noisy and mostly boring. It's the gradient coils that make the noise.
John
thank u very much u just raised my hope i thought that our universities in egypt are so what too say primative in practical and specially in analog design but for a change i think analog/mixed design is reviving again it's the chance i my self am designing a VGA for a communication channel AFE well it may be a sand particale compared to the whole design but those digital geeks using VHDL and denying the ability of human to get new designs of his own can't do it never because it just need the talent and someone loves Transistors Analog era will never end it's the backbone of every thing even digital they just need the finnest as they need less numbers these days any way if someone knows a college in US that will help an egyption student like me to get his master at in analog/mixed design (considering i can't be a penny) i'll be glad of him
yours gad elsayed,mina
I certainly would not say "vast". Many times I have pondered the use of a uC in a design only to come to the conclusion that 50c is still too expensive. It's amazing how cheap "poor-man's logic" can be.
It sure is disappearing, just like analog skills seem to be almost gone in fresh grad.
I've ripped out many uC solutions for reliability and cost reasons. Same for PALs/GALs because that's the era back in the late 80's when mixed/discrete design skills began to tank. The topper was a system where I ripped out so many (plus went to 100% AC terminations) that the power supply kept tripping off and one of them blew. We had managed to get underneath the minimum load. IIRC the PALs was guzzling 30-40mA just sitting there. Each.
What's the old saying? If they only learn how to use a hammer every problem will begin to look like a nail. Heck, I've seen one-shots being done with a uC. That almost made me sick.
-- Regards, Joerg http://www.analogconsultants.com
Did they use a RTOS ?
VLV
US universities tend to be quite expensive and I bet the cost of living is also much higher here than in your country. Why can't you get the degree in Egypt? And why do you really need a master? Ok, I've got that degree myself but honestly nobody ever asked about it or actually wanted to see the degree, except government agencies. All they wanted to know is whether I could solve their problem and how long the redesign would take.
-- Regards, Joerg http://www.analogconsultants.com
I used to be opposed to using a tiny microcontroller to do something "simple" like flash an LED in various patterns depending on, say, 2 or 3 inputs, but these days I think it's often justifiable if only from the standpoint of scheduling: Cranking out all of 20 lines of C code is a lot faster than doing the "discrete" design. With tiny microcontrollers going for ~$0.25 these days in 100-ish quantities, it's pretty hard to justify even a day spend on a discrete design for low quantities (
I just took apart a transducer, they used two PICs as comparators...
-- John Devereux
It probably could be done for very high volume where it is warranted to put a lot of engineering hours into it. Some of my designs are like that. You sit there agonizing over a BSS123 because it costs about two pennies more than a BJT. Then after half an hour a light bulb goes off and you figure you can really do it with a BJT plus a resistor, saving
15 milli-Dollars per unit.Which uC were you thinking about? 25c with ADC on board sounds like a good deal. But only if it doesn't need a crystal or resonator.
Of course, Jim would say that he just puts it all into Spice and then has the chips made.
-- Regards, Joerg http://www.analogconsultants.com
2N7002 would probably save two pennies plus the stuffing cost of the resistor.
VLV
Usually not, it's around 3.5c, plus Vds doesn't suffice for many apps. Stuffing costs are extremely low (China) and I always calculate the total.
-- Regards, Joerg http://www.analogconsultants.com
Ah, I misunderstood you incorrectly.
My mother had a head MRI many years ago to try to find the cause of some balance problems. During the consultation after, the doctor told her that they didn't find anything, thought for a second, and started apologizing profusely after she burst out laughing.
I was wondering. It sounded like something moving around in there. They warned me of the noise and offered ear-plugs. It wasn't *that* bad. It *was* close, though.
-- Keith
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