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Linear 3.3V power supply anywhere?

That's nice, although I wouldn't want to milk 800mA from a BC327.

robert

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Robert Latest
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The cheapest 2A transistor is sometimes a FET these days.

I'd have whipped up my usual partial Schmitt-Inverter switcher but this time it cannot be anything that switches.

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Regards, Joerg

http://www.analogconsultants.com
Reply to
Joerg

Not much. It's done. I cheated and modified an off-the-shelf supply. So I didn't have to draft a new one in CAD but could take my wife out to the Thai place instead :-)

But I am not really a fan of paralleling LM317's. If you need more current than it can supply it's better to bootstrap one or more transistors across it.

--
Regards, Joerg

http://www.analogconsultants.com
Reply to
Joerg

I won't touch LDOs with a ten-foot pole anymore. Seen too much grief.

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Regards, Joerg

http://www.analogconsultants.com
Reply to
Joerg

Gosh, does anybody still make those "junction" things?

I did a nice closed-loop high-voltage inverter using a TinyLogic schmitt oscillator driving a 2N7002. Very low power. I've got it around here somewhere...

John

Reply to
John Larkin

ON, Fairchild etc. You can still buy ye olde TIP31 for around 15c in qties. Also some BD and BU types. FETs often win the cost game these days except for really high voltages around 1kV. Although ST has made some inroads into the sub-30c region up there.

Now when does Digikey begin to allow "search by price" or at least sort the results by price? Or default to in-stock only instead of having to click twice...

After the first time I did that (CD40106) I began to wonder why people paid so much money for PWM chips and go the risk of single-source. Sole source was actually the reason why I did that Schmitt design for a client back then. Rebecca's company couldn't cough up production quantities, so...

Question re 3.3V: Do you or another newsgroup participant know where to get a crowbar module for 3.3V? The OVP-24 from PowerOne won't go below

6.2V. It should have a tolerance band that prevents logic chips from croaking when the regulator goes lalaland. Probably 4V max or so. 
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Regards, Joerg

http://www.analogconsultants.com
Reply to
Joerg

Has anyone made a polyphase sine converter where absolutely no buzz is required? That converter only has 1 harmonic (mostly). D from BC

Reply to
D from BC

Do you mean a 12V to 120V inverter?

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Regards, Joerg

http://www.analogconsultants.com
Reply to
Joerg

TL431 ? Ed

Reply to
ehsjr

I'm not sure but I think the automotive inverters have a quasi-sine output.

I mean this crazyass idea.. It uses many power sine oscillators but with different phases. The outputs drive a polyphase transformer. I think it can be done with a phase shift oscillator and a few audio power amplifiers.

For 6.6Watt delivery, this method will probably be more toasty than a linear regulator.. But it's another way :) D from BC

Reply to
D from BC

Nope. You could make one. How about just a string of power diodes? Three or four 35-amp bolt-down, faston-lugged bridge rectifiers wired in series with outputs shorted?

Or a small bandgap reference, LM4040 sort of thing, driving an emitter follower, driving a big scr? The gate drive doesn't snap, but a bigish scr shouldn't mind.

Ooh, how about a bandgap zener driving a small scr "cathode follower" driving a big scr! That would be pleasingly weird.

John

Reply to
John Larkin

I

Actually I just had a quick email exchange with Condor because we need all this somewhat "officially" blessed. Very helpful engineers there, Condor (now SL Power) is a great company. Right after lunch they returned my 2nd request with a perfect answer. In case anyone else needs a nice crowbar module:

Condor OV-12, Mouser P/N 675-OV12-G, around $8. Best of all it's in stock. Not at Digikey though. $8 is an ok price for the electronics I am designing right now, it's more in your range of products. Smaller volume, high end. Looks like the precision of this crowbar can easily be boosted by replacing a zener with a LMV431. Sweet.

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Regards, Joerg

http://www.analogconsultants.com
Reply to
Joerg

You can get sine wave inverters but they cost more. A lot more. IIRC one company (Statpower?) calls theirs "TrueSine". No costly transformers here. Basically you just generate a fast PWM where the duty cycle follows the sine. Camping and marine supply store carry those.

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Regards, Joerg

http://www.analogconsultants.com
Reply to
Joerg

That's almost what I am going to use. We need a crowbar module with the right certs and all. Per suggestion from Condor Applications Engineering we'll take their OV12 module, yank the zener and replace it with something like a LMV or TLV431.

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Regards, Joerg

http://www.analogconsultants.com
Reply to
Joerg

Hi Jörg,

Taht's the difference between such engineers tha can plug and play high-level IC and others that can built these with discretes...

Hi Jörg, what's happen with you? TL431 a simple pnp and a thyristor of your cheapest selection. OK 3 Resistors two for the 431 and one between base and TL431. Do you need more? Yes, the fuse :-) Don't forget to place the anode from SCR before the 3V3 regulator.

Marte

Reply to
Marte Schwarz

After having met lots of younger grads I am wondering what will happen after we are all gone.

This is a low volume product and we need something out of a can. Turns out Condor has that, the OV-12. It just needs a better zener, meaning a LMV431 and it'll be good enough.

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Regards, Joerg

http://www.analogconsultants.com
Reply to
Joerg

What's wrong with something like LT1764A? 3A, available in up to 3.3V That just happens to be one I have a couple of. Digikey has it in DD5 and TO220-5, but they're a bit spendy.

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Ben Jackson AD7GD

http://www.ben.com/
Reply to
Ben Jackson

Well, this is medical and everything newly designed needs to go through the usual hoops. Also, the LT1764 is a LDO and I am pretty much cured of using those. A quote from the LT1764 data sheet might illustrate the point: "Ceramic capacitors have extremely low ESR, and while they are a good choice in many cases, placing a small series resistance element will sometimes achieve optimum stability and minimize ringing."

That gives me the goose pimples. Sounds like marketing speak for "it could go ballistic if you don't watch the ESR". At least they offer a table on page 12 but still, I'd rather not.

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Regards, Joerg

http://www.analogconsultants.com
Reply to
Joerg

The regulator is DC coupled, has a single-ended output, more gain, and much higher bandwidth.

Bye. Jasen

Reply to
jasen

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IRU1030-33

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vasile

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