A small rant about the 555 :-)

It was pinned out to accommodate how the transistors fit together compactly during layout... back when silicon was expensive. Now silicon is dirt cheap... and packaging is expensive. ...Jim Thompson

Tell that to Slowman.

Pinouts never bothered me. That's the layout guy's problem. ;-) After a few BGAs they don't sweat the small stuff either.

You obviously know nothing about electronics. Just ask Slowman. ;-)

Funny. I'm not tired at all.

There are other timers. For ex., MIC1557.

I never draw schematics with the pins arranged in physical order. We create schematic symbols that look logical and that have pins where they make sense.

But I haven't used a 555 in decades. It's a pretty crude beast.

'Night.

John

John Fields would be more interested. It has never turned out to be useful for the work I've done.

I hate engineers who don't think about the layout they are effectively asking for. Any circuit where stray capacitance or inductance can be a problem should be designed with the layout in mind.

He seems to know more about electronics than krw does, but that isn't unexpected.

-- Bill Sloman, Nijmegen

I'm thinking Camenzind wasn't expecting anyone to use the 555 much above a MHz or so when he designed the thing. At those frequencies, the IC's layout/pinout just isn't going to matter.

Didn't Hans used to occasionally post here?

---Joel

I don't have any problems finding a job. What are you doing, Slowman? Still whining about your station in life, I see.

I probably shouldn't be saying this, but if some individuals spent a little less time feeling embittered and sorry for themselves and instead tried to get on with people, they would find many willing to help out and give them work.

If you don't respect yourself and hold the line re your own worst sentiments, how can you expect others to ?...

Regards,

Chris

I used them years ago for microprocessor reset duty. Dirt cheap, minimum associated parts count and sure fire operation every time. Most designs here need a hardware watchdog now and the processors are 3,3v, so 555 is essentially obsolete.

I was thinking the other day about how some analog devices, like 741, lm311 and others like lm348 seem to have a charmed life. Designed 30 odd years ago and still going strong. I guess it's an indication of how right they were from the start...

Regards,

Chris

;-)

I can't say that I've got anything to whine about. I'd prefer to have a job, but I can get by without one.

-- Bill Sloman, Nijmegen

It is a pity krw won't pay any attention to your well-intentioned preaching.

-- Bill Sloman, Nijmegen

The LM311 was always a good device - to quote Winfield Hill

" One of Robert Widlar's fine designs. Rather expensive when it first came out, but now pretty cheap. NSC has a 1970 appnote he wrote on the part, AN-41.

One caution, although it can run on 5V, and has PNP input transistors, like the LM339, LM2901, LM3302, LM393, LM2903, etc., it can't work all the way down to zero volts. But, unlike those parts, it can deal with a +/-5 to 15V split supply with a grounded output load switch. It can also do high-side load switching. Pretty impressive for 1969."

It is difficult to provoke it into oscillation, though I have seen it done.

The uA741 and uA748 aren't in the same class. The lateral PNP in the output stage has a very low current gain and is as slow as a wet week. If you draw an appreciable current through it while the output is close to the negative rail, the op amp can oscillate.

Bob Widlar solved the problem rather more cleverly in the LM301/307 by using a lateral PNP as the driver in a complementary Darlington.

The persistence of the uA741 and uA748 has more to do with engineers who recycle old designs without thinking how they might be improved by employing more modern components. The persistence of the 555 owes a lot to this kind of inertia, though to be fair to the 555, the original design left rather less room for improvement than that of the uA741 and the uA748.

-- Bill Sloman, Nijmegen

Except that no one "gives" anyone work. It's a contract like any other. You have something to offer that someone else needs. Slowman obviously doesn't fit the bill and projects his incompetence on others. That's the leftist weenie way.

When you have nothing to offer, whining is all that you can do. A politician, somewhere, will cater to your whining, and trade you a biscuit for your soul.

Yet you project your inadequacies on others. ...and whine. Trypical leftist loser.

Regardless of the misplaced pronouns, he ain't preaching at me, dumbass. I'm not the unemployable one.

I've never had trouble arranging the connections of the LM555. The 8 pin DIP doesn't contain enough "corner paint" to cause major concerns. There are lots of other chips that are more trouble to lay out.

I still use them occasionally. Two opamps for 8 cents.

John

My designs from the '60's can still be purchased...

I didn't really mean that it's a "major" problem. What I meant was that, for a simple circuit serving a simple purpose, albeit a useful and versatile one, the illogical placement of pins makes things more difficult than they could be.

For example, if pin 8 is Vcc, it would be better if ground was 5, and the control voltage terminal at 4. Then connecting the bypass cap from pin 4 would also be easier. Since the reset pin is often tied to Vcc, it could be allocated to pin 1. It wouldn't cause a problem with external triggering. I'd also interchange 2 and 3 - that will make a straight track from 2 to 6 in astable mode. So this is what I'd do: _________ Reset 1-| |-8 Vcc | | Output 2-| |-7 Discharge | | Trigger 3-| |-6 Threshold | | Control 4-|_______|-5 Gnd

Of course, all this is academic since the 555 has been around as it is for almost 40 years. But just visuallise drawing a schematic or designing a pcb with my mythical IC. I think you'll find that it's much easier.