Original crispy flavor MicroSim PSpice Schematics. I've been using PSpice, starting in DOS, when the only netlist-able schematic capture was the original OrCAD. So I pencil drew schematics, numbered nodes, then typed in a netlist. My son, Aaron, wrote me a version handler that maintained a stack of the revisions, in case I needed to back up ;-)
...Jim Thompson
It does not!
A silicon drop will *not* prevent a 339 from going wonky if you pull an input below ground. That -0.3 volt max spec is, if anything, right on the edge. Look at the zcd example on the National data sheet. After the diode clamp, they shift positive. The other examples, where they do use a diode clamp, and conveniently vague about V-.
Besides, those of
OK, why can't it happen? You're going to get about a mA peak through D3, which will pull the 339 input maybe 0.65 below ground. That's over twice the -0.3 max, which the data sheet cautions against in at least four different places.
I've seen it happen with the National parts, and a silicon diode didn't fix it. Maybe other vendors' clones aren't as bad.
The LM339 is at least 35 years old. Strange that National never bothered to fix this. All they have done in those decades is make the warnings more obvious.
National's LM324 has that same problem, and others.
Provided that Digikey doesn't run out of behavioural 339s. ;)
Cheers
Phil Hobbs
They want to sell you more expensive parts. 339s are good and useful for sufficiently slow things, as well as being dirt cheap, like under $200 per reel even from distributors.
Cheers
Phil Hobbs
Yep :-D ...Jim Thompson
The behavioral ones are even cheaper ;-) ...Jim Thompson
I've never looked at running it at that low a voltage. I think you would run into the same issues with diode drops making it straddle zero funky. I'll drop the input resistors to match that voltage level and see what it does. I'll let you know.
So, I guess the Vcc that is in the PDF is there to supply the current for the internal LED flash light, in case the electrons want to look back to see where they have just came from!
Interesting, that some fancy silicon..
Jamie
Cheers
Phil Hobbs
So spricht der Sykophant
...Jim Thompson
So sprechen Sie die sychophant
Liebe herr unbekannt: I gather you don't have any friends. John is one of mine. He doesn't need my help to defend himself in this company, of course, but most of the time we're on the same page.
What's German for "mutual regard"?
Cheers
Phil Hobbs
Dear Mr. Friday: You seem to be repeating yourself. Are you JT's sockpuppet or what?
Cheers
Phil Hobbs
Of course it's derogatory. It means "bad circuit."
If it's *your* bad circuit, you might take it personally.
Yup, that's exactly right. I have built a non-zero-cross detecting version of the circuit and it switches fine, but damn! it clicks on both closing and opening the MOSFET switch. I haven't yet measured the minimal voltage or current -- the load is a 6 ohm woofer -- at which the click is audible, but I am assuming somewhere in the 10mA-100mA range. My idea is to use the PIC's edge detect feature to trigger an interrupt when the zero cross has occurred, and open or close the switch at that point if necessary.
Signal level (0-13.8 V) AC-coupled. The circuit will be battery powered, so single supply. The basic idea is to use a ZCD to trigger a uController that is handling the gating function. I want avoid "clicks" in the woofer when the audio is cut or reenabled. I'm not sure yet at what voltage level the clicking will cease, but some basic tests with a 9V battery, a pot and a speaker tell me that it doesn't take much to make a woofer go 'pop', probably < 1 mV.
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