LM723 die pictures

[Noopy]

I decided to open a new thread. I hope that´s ok for everybody. In the 555-thread it would be to far off topic.


In the 555-die-thread Wolfgang asked for pictures of the LM723:
https://www.eevblog.com/forum/projects/some-555-timer-dies/msg2870226/#msg2870226

Done that:






Link to my site:
https://www.richis-lab.de/LM723.htm


I didn´t write very much about it because Wolfgang has already written a lot:
https://electronicprojectsforfun.wordpress.com/power-supplies/a-collection-of-proper-design-practices-using-the-lm723-ic-regulator/

What I realized looking at the die:
It seems that the design is the one you can find in the older datasheet. The schematic in the current datasheet is much more complicated.
I couldn´t figure out when this LM723 was produced but it didn´t look too old to me.
Perhaps I should decap one more LM723... 


Greetings,


Richard

[wraper]

It seems that the design is the one you can find in the older datasheet. The schematic in the current datasheet is much more complicated.

No wonder. On the photo on your website IC looks to be salvaged, sanded, blacktopped and marked again. Look on the tiny holes in ST logo.

[Noopy]

Hm, didn´t see that at once but probably you are right. 
I think I have to dedcap one more... 

[BravoV]

Have a bunch of these, given by my mentor many-many years ago.

PM me your address, once I get home (currently on travel), I will send you this TO-200 can type 723.

PS : I will be sending used one.

[Noopy]

Hello BravoV,

thanks for your offer. 
I will send you my adress.

[David Hess]

It seems that the design is the one you can find in the older datasheet. The schematic in the current datasheet is much more complicated.

The published schematics are often considerably simplified like with the common 324/358 schematics although I understand that there is more than one version of the 723.

[Noopy]

The published schematics are often considerably simplified like with the common 324/358 schematics although I understand that there is more than one version of the 723.

In this case the circuit on the die is simpler than the newer shematics.
There are definitely missing a lot of parts on "my" die.

I definitely need a new one… 

[magic]

The "new" schematic may be a redesign by National.

Wolfgang's website has an old µa723 application note from Fairchild which shows a schematic very similar to your die.
An even more accurate match is the schematic from Motorola datasheet, but there are a few dumb and confusing errors. The circuit wouldn't ever work as drawn
Old TI datasheet (before National acquisition) also shows the same schematic as Motorola, without errors.

So there is quite a bit of agreement, and only National sticks out as the weird one. Some datasheets (ST, Philips) have no schematic at all.

And since Texas Instruments absolutely has no taste and looking at their schematics makes me want to throw up, I post corrected Motorola schematic below, which appears to match your die. Enjoy

edit
Added the Fairchild schematic for completeness. The only difference I can see is Q9 and Q11 collectors. I have no idea if the original Fairchild die matched the Fairchild schematic or maybe was like everybody else's.

I also don't understand what was the point of connecting Q9 and Q11 collectors to Q4 and Q5. VCC is available in the isolation well right underneath Q4 and Q5, they could have used that if they wanted to.

[iMo]

FYI - TESLA's MAA723 (with 4 additional resistors)
PS: they did DIL14 and metal can

[floobydust]

The uA723 I believe was originally developed by Bob Widlar in 1967 not sure who developed it (it incorporates his current source). Oldest oldest data I can find is from Fairchild 1971 attached schematic.

Wikipedia: "Widlar's productivity was so great that it has stimulated spurious attributions. A prevalent example erroneously credits him with the design of the μA723 voltage regulator. However, not only was that chip released some two years after Widlar's departure from Fairchild, the circuit employs, and relies on, greatly improved lateral PNP transistors that were not available during the period of Widlar's employment at Fairchild. Credit for the μA723 properly belongs to Darryl Lieux, according to his contemporary (and father of the 741), Dave Fullagar. [48]'

National Semiconductor AN-1 (yes app note #1) November 1967 is all about the LM100 which is quite similar to the uA723 but likely got snarled in patent litigation. The voltage reference, foldback current-limiting all were patented blocks between National and Fairchild, which maybe why the LM100 didn't make it.

edit: 1973 databook here: https://archive.org/details/bitsavers_fairchilddldLinearIntegratedCircuitsDataCatalog_30443462
edit2: 1968 Fairchild uA723 App note http://www.ve6aqo.com/old_manuals.htm

[Noopy]

Thanks for all your input!

I will have to collect some more of the LM723-variants. 

[magic]

So a few remarks for Wolfgang, if you are reading this

It wasn't exactly the legendary Widlar and, pending further research, the National schematic may not even be true to the original Fairchild design.

And I also doubt it's a buried zener. Looks like any other NPN BE junction visually and the Fairchild appnote (page 1.12) brags about a state of the art process capable of integrating even N-JFETs and capacitors in addition to NPNs and PNPs

[iMo]

No buried zener in 723. And frankly, I doubt there is even a zener as the Vref.
The Vref is quite noisy, I saw 2mV p-p noise there, moreover, Wolfgang confirmed that in his measurements.
PS: I like the 723 (because I built my first PSU around it). On the other hand the stories about its "Vref stability and low noise" are just urban myths, imho.

[magic]

Of course there are two zeners: one for Vref and one for bias generation.

The bottom right pad is the buffered Vref output. Next one above is the GND pad. Between them is the 5pF compensation capacitor and two NPNs: Q6 on the right, and D2 on the left. The BE junction is used, just like for D1 elsewhere.

[iMo]

Is that a real zener or a reverse biased transistor junction?

[magic]

No idea. Looks like any other junction and they don't brag about any special technology in the appnote or datasheet so probably a fake zener, if reverse biased transistors aren't real zeners

[floobydust]

Noopy, thanks for the archaeological digs.

I find it odd the uA723 won the wars. The 1968 Fairchild App note shows the LM100 schematic... 
Most claims for better performance are due to better IC technology - compensation capacitors, lateral PNP's - but it might have been price or lack of military use that sank the LM105. Application Note 23 - The LM105- An Improved Positive Regulator Robert Widlar January 1969 explains the LM100 limitations, zener noise etc.
Many National Semi IC's came and went, in the 1970's, despite them being fine parts.

About the V reference design, it's mentioned in AN-1 the differences between using a reverse-biased EB junction and avalanche diode, for best tempco. A second goal is compatibility with the IC process so 'surface impurity concentrations' do not need to be specialized. I have a paper databook with AN-1 but could not find on the web.

[magic]

About the V reference design, it's mentioned in AN-1 the differences between using a reverse-biased EB junction and avalanche diode, for best tempco. A second goal is compatibility with the IC process so 'surface impurity concentrations' do not need to be specialized. I have a paper databook with AN-1 but could not find on the web.

Attached

It's included in National's 1973 Linear Applications book and you can find scans of that.

Typing "the first buried zener reference" into web search, I also found this book, which claims that this technology was introduced by the familiar LM199/399.
https://books.google.com/books?id=03JmxpE39N4C&pg=PA7&lpg=PA7&dq=the+first+buried+zener&source=bl&ots=5yhwN6_hv9&sig=ACfU3U0SGgYYnUaYj1lyauVYqAOng6TQHQ&hl=pl&sa=X&redir_esc=y

And back to

what was the point of connecting Q9 and Q11 collectors to Q4 and Q5.

I suppose it's for better power supply rejection. And a side effect is limitation of the regulation amplifier's common mode input range to a diode drop or two above Vref, which means that this tweak was likely not introduced by second sources but by Fairchild themselves. Apparently they concealed it in the documentation to protect their secret sauce

[BravoV]

Two of these are on their way to Noopy. 

National Semiconductor LM723CH date code 8848, and Fairchild UA723HC date code 8335.

[Noopy]

Nice!

And I found a LM723JC (ceramic package) built by National semiconductor. 

[David Hess]

Below are a pair of Fairchild ceramic packaged 723s in my Tektronix DC505 universal counter which came from NASA's Glenn Research Center.  The photograph shows how I replaced the original Texas Instruments edge wipe plastic DIP sockets which were damaged by the hot operating 723s with collet pins.

[EEEnthusiast]

Nice hand drawn PCB artwork...

[Noopy]

And here is the LM723JC:


https://www.richis-lab.de/LM723_01.htm





Looks very different but you can find the similar blocks in the ST Microelectronics LM723CN.

The resistor in the upper right corner looks interesting. 

Below are a pair of Fairchild ceramic packaged 723s in my Tektronix DC505 universal counter which came from NASA's Glenn Research Center.  The photograph shows how I replaced the original Texas Instruments edge wipe plastic DIP sockets which were damaged by the hot operating 723s with collet pins.

Nice! 

[magic]

No, it looks the same. No way in hell that this matches the schematic from current National/TI datasheet.

Look at the reference circuit, it's all the same. Same compensation capacitor near VREF and GND pads, formed by a metal layer over the large collector area of Q6. Same two BE junctions over that collector just north of the capacitor, one is the actual Q6, the other is D2. Same long resistor from D2 anode to ground and another one to Q6 base. Q6 collector again is loaded with a PNP current source and drives a Darlington pair which drives the zener cathode through a resistor. For whatever reason, they moved the bottom transistor of that pair to the left side of the die, near the COMP pad.

It seems they added some base resistance to the current limit transistor and there are only 3 PNPs. There are four, but two of them use the same emitter connection point on the die.

The weird resistor in the upper right seems like part of the biasing circuit, perhaps it's the N-JFET. There are similar structure on a lot of analog opamps and I frankly never quite fully understood how it works.

edit
Not sure if it means that there are two versions of National LM723 or maybe you just bought this part from AliExpress

[iMo]

Here is a 723 schematics from electronicprojectsforfun page, with the current sense base resistor (and even more mess):