Instead of TL783's

Hi folks:

Well, it looks like the TL783 high(ish) voltage 3-terminal adjustable regulator is defunct. At least, Digi-Key, Allied and Mouser no longer stock it, and Mouser explicitly says it's discontinued.

So...in years past, before the TL783 was easily available in small quantities, I made 48V phantom regulators by suspending an LM317HV on a 47V zener diode. (National Semi calls this "floating" but it isn't really, so I'm using "suspending" as a verb pending a better one. The zener diode, with a 470µF cap bypassing it, replaces the adjusting resistor.) This is outside spec for the LM317HV, technically, but I've been using the mixer containing that circuit for some 22 years now, and it hasn't quit yet. Still, it makes me nervous.

So have any of you used LM317HV's this way? Were they reliable?

Peace,
Paul

Hii,

check these out:

VB408 from http://www.st.com

LR08 from http://www.supertex.com

Alex

Thanks, Alex!

VB408 sure looks interesting for our purposes.

btw - I think the rumours of TL783's discontinuing are wrong. Yes, Texas won't continue these, but there's many companies making them..

Jakob E.

Pstamler,

Yes i've used the "floating/suspending" with the LM317(and other non-adjustable regulators) for various voltages. I'd say that it works fairly well too but haven't done many in depth tests on regulation since most of the applications weren't in need of serious precision.

i would bet though that it would work just as good as expected since all you are doing is changing the ground sense, making it think that ground is at a much higher potential than it is.

EDIT: I just came across a schematic for a PSU that really does use the lm317 for phantom powering, however it changes the ground through resistor networks..

:thumb:

I read somewhere (i think on the DIY-G9 section on the gyraf site) that using regulators for higher than specified voltages is ok as long as you don't accidentally short the output to ground.

yeah that's a given for any design though, no regulator appreciates being shorted, especially when it's a short beyond the rated voltage of the part.. :green: but hey, everyone likes fireworks right? :green:

I think the supertex LR12 might work. It comes in a TO-92 so, you may be able to drop it into an existing board.
You can buy it at mouser.

Datasheet:
http://www.supertex.com/pdf/datasheets/LR12.pdf

The LR8 seems to be a bit low on current, but with a pass transistor I think it could make a nice tube preamp voltage regulator.

OK
someone help me out.
I spent 10 minutes ob the ST website
and could not find VB408?
I must be an idiot.

Maybe I`m stupid,
but I can not find this VB408 on the www.st.com sait ???

--Bo

> I can not find this VB408 on the www.st.com sait ???

Apparently already discontinued. A Google search finds other folks who can't find it, or only at steep prices.

Thanks PRR,
you save my self-confidence.

Now I can reach the ST and the VB408 document via Goggle, but not on the company`s site search, starnge ???

--Bo

[quote author="gyraf"]btw - I think the rumours of TL783's discontinuing are wrong. Yes, Texas won't continue these, but there's many companies making them..[/quote]

I did a Google search, couldn't find any second (or third or fourth...) sources.

Peace,
Paul

Look for TL783CKC. RS has em.

That must be old stock at RS, cuz TI says that part number is going away as well.

Yes, I didn't find any alternative sources either - though I'm pretty sure I've had those from different manufacturers.

But I find it hard to believe that a standard part like this would simply go away. Also, TI would always give you fair warning before discontinuing a well-known unit like this. And the datasheet is updated as late as 2004..

Don't worry too much about it (just yet...)

Jakob E.

TI still makes the TL783CKTER which is a surface mount part.
Digi-Key has 630 in stock @ USD$1.60
The surfave mount case will be hard to suck the heat
out of. But someone could make a small board with right angle
pins and still use this part for our favorite application phantom
supplies. I have never seen a sub for this part.
Please send me the datasheet and prove me wrong.
This part does sound good as a voltage regulator.
The LM317 family sounds gritty by comparison. I assume
the DMOS vs. bipolar transistor pass element may be the difference.