regulator thingie

LP2951 is still available, might be suitable... somewhat.

The offboard pass transistor might be better run by a four-terminal regulator rather than a three-terminal type; the addition of a current sense resistor is simplified somewhat if you do it that way.

one of the first hits on google is UC2836D digikey have some, though not cheap at ~10$

-Lasse

Interesting part. Unitrode datasheet from 1994. Yes, it is a bit expensive.

Looks like the best bet is to use an LM723, which is a, what, 40 year old chip?

Lots of people still make the 723, and all the datasheets seem to be cribbed from the Fairchild original. And none discusses compensation in any detail. It's impressively under-specified. I suppose I'll hang a big cap on the comp pin, maybe a series R for luck, or else go into the schematic and analyze the beast.

John

How about this supplier:

$1.75 in single quantities. Don't know how many they have but worth a try.

It crosses to NTE1930 and ECG1930 exact replacements and you can still find those in stock although obsolete too.

It looks like the current limit on the UC3836 is permanently wired for 2.5A (maybe you could parallel a resistor to get it to go higher, but not lower). uA723/LM723 is OK for higher voltages (9.5V minimum input) and LP2951 for low voltages (2V to 30V input range).

None of these is a straight substitute for the LM376, though.

According to

"LM376 was an LM305 in a plastic DIP package"

Which can still be found, but not cheap by any means.

I used to like the LM611/613/614 for that job.

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC
Optics Electro-optics Photonics Analog Electronics

55 Orchard Rd
Briarcliff Manor NY 10510
845-480-2058

email: hobbs (atsign) electrooptical (period) net
http://electrooptical.net

I don't think any of them are still in production, and old parts from brokers are risky.

Looks like a ua723 will do what I want, but it has a lot of constraints. I was just sort of surprised that nothing like the 376 is still made. What do people do when they need a big honking linear power supply? Make the controller from a reference and a couple of opamps and a transistor or two, I guess... a lot of parts to replace one DIP8. Seems strange that the best, basically only, linear regulator controller left, the 723, is about 40 years old.

John

I'm reading it like: use internal shunt between pin1 and pin8 or add you own shunt between pin1 and pin7 and leave pin8 open

-Lasse

Is this any good?

Uses a N MOSFET as the pass element instead of a PNP so not a drop-in replacement.

I used one, ages ago, on a dev board. No stability issues, it just worked. It seems to still be in production, Digikey has them in stock.

HTH

R.

Unfortunately, it won't work with my constraints.

But it is a cool part. I was just doodling a new project idea this morning, and it would need a bunch of adjustable regulators with precise current limiting, and this might be just the ticket.

John

Linear has more stable linear regulators. The 5156's 2% is'nt that great. But micrel does have some neat stuff, particularly their high side drivers since they can switch right up to the rails.

Cheers

They use a 723 and some big honking transistors on a massive heat sink. Take a look at linear bricks (PowerOne and such), those are a reason the

723 is still around and will be for a long time.

40 years is no problem for a successful part, and the 723 clearly qualifies as successful. Right up there with the LM317 or Bob Pease's LM337. I remember when a Fairchild sales guy in the 90's wanted to convince me that it would be futile if I designed a circuit with CD4000 logic because it'll go obsolete. His new logic parts were more expensive and would have needed a regulator, so naturally I didn't listen. Actually I had a mild ROFL episode about it later. Long story short that unit still rolls off the production floor in quantities in Shenzhen today.

There's app notes about the LM723. If you can't find anything I can go through my stash (there's a reason I don't throw out the old printed app notes and databooks). But it'll have to be later because today is the day where SWMBO wants us to move a massive fountain to another spot. Which of course is higher up and can only be reached via rocks. Anyone have a Motrin?

--
Regards, Joerg

http://www.analogconsultants.com/

"gmail" domain blocked because of excessive spam.
Use another domain or send PM.

The good thing is LTC usually doesn't obsolete stuff until they have called pretty much anyone who has ever bought one of those parts, and no orders have come in during the last few years. Just to make sure. But prices are often a bit steep.

--
Regards, Joerg

http://www.analogconsultants.com/

"gmail" domain blocked because of excessive spam.
Use another domain or send PM.

Why not an OpAmp, a reference (say a TL431), plus your power device... can't anyone think feedback anymore? ...Jim Thompson

--
| James E.Thompson, CTO                            |    mens     |
| Analog Innovations, Inc.                         |     et      |
| Analog/Mixed-Signal ASIC's and Discrete Systems  |    manus    |
| Phoenix, Arizona  85048    Skype: Contacts Only  |             |
| Voice:(480)460-2350  Fax: Available upon request |  Brass Rat  |
| E-mail Icon at http://www.analog-innovations.com |    1962     |
             
I love to cook with wine.     Sometimes I even put it in the food.

Sure, but you have to add lots of stuff. Typically, you'd also want over-current limitation and such things. The 723 has all that nicely tucked into a single package.

If you can get all this in a 25c industry standard chip why would anyone want to build it with more parts and at higher cost than necessary?

--
Regards, Joerg

http://www.analogconsultants.com/

"gmail" domain blocked because of excessive spam.
Use another domain or send PM.

Sometimes one designs for quality and reliability.

But sometimes even _I_ squeeze to save space... just recently, pondering how to do a _full-swing_ wired-OR from a pair of inverters (NOT open drain), I remembered the input stage of TTL... 2 NPN's plus one resistor :-) ...Jim Thompson

--
| James E.Thompson, CTO                            |    mens     |
| Analog Innovations, Inc.                         |     et      |
| Analog/Mixed-Signal ASIC's and Discrete Systems  |    manus    |
| Phoenix, Arizona  85048    Skype: Contacts Only  |             |
| Voice:(480)460-2350  Fax: Available upon request |  Brass Rat  |
| E-mail Icon at http://www.analog-innovations.com |    1962     |
             
I love to cook with wine.     Sometimes I even put it in the food.

The 723 is horribly under-specified. All the datasheets seem to be identical copies of the (Fairchild?) original. If you want to know the error amp bias current, you have to look at the schematic and estimate it, or measure it. It's not specified.

Apparently the design was pre-bandgap, so it's full of zeners. So it won't work below 9.5 volts input. The reference out voltage exceeds the max allowed input differential voltage, so you need a voltage divider there. The current limit sense needs a full junction drop across the sense resistor.

National specs its ESD tolerance as 1200 volts!

It was brilliant 40 years ago. I'm just surprised that it's still about as good as you can buy.

John