Aren't capacitors needed just for smoothing out the voltage for frequency stuff ? (sorry if my questions are dumb)

I was the one who wrote this data sheet including the section explaining how and why the caps are essential to make it stable.

Imagine how happy I would be if someone..... anyone.... would actually read it.

 

I was the one who wrote this data sheet including the section explaining how and why the caps are essential to make it stable.

Imagine how happy I would be if someone..... anyone.... would actually read it.

Do you seriously write data sheets, BH?


My hat is off to you, Sir.
To me, some of those sheets are mind-boggling.

 

I was the one who wrote this data sheet including the section explaining how and why the caps are essential to make it stable.

Imagine how happy I would be if someone..... anyone.... would actually read it.

See post #18. I read it!

 

If you really want serious help then let's get serious.

1) Provide the full part number.

2) Use input and output capacitors as recommended in the data sheet.

b.h. is not kidding.

 

See rule #8 here...... http://www.freemeditation.com/artic...from-albert-einstein-quotes-and-inspirations/

 

Do you seriously write data sheets, BH?


My hat is off to you, Sir.
To me, some of those sheets are mind-boggling.

I worked at National Semiconductor for 20 years. I wrote (or re wrote) so many of their linear data sheets I don't even remember them all. But this 2940/1 series I remember because the part was a major pain in the rear because of the restrictive ESR requirements on the caps to maintain stability. About 99% of caps don't work, especially over cold temperatures and this dog made my phone ring all the time.

 

I was the one who wrote this data sheet including the section explaining how and why the caps are essential to make it stable.

Imagine how happy I would be if someone..... anyone.... would actually read it.

I read it bountyhunter. It was wonderful

 

I read it bountyhunter. It was wonderful

Yes, even the parts I don't understand were written beautifully.

 

Yes, even the parts I don't understand were written beautifully.

Agreed, I really like the part we he described that sunset. It was almost like being there.

 

I was the one who wrote this data sheet including the section explaining how and why the caps are essential to make it stable.

Imagine how happy I would be if someone..... anyone.... would actually read it.

I share your frustration. I read data sheets thoroughly but many newbees don't, perhaps because they find them intimidating. But many times they ask questions that are readily answered by the data sheet.

 

I share your frustration. I read data sheets thoroughly but many newbees don't, perhaps because they find them intimidating. But many times they ask questions that are readily answered by the data sheet.

I do find them difficult to read but most of the design notes are fairly straight forward. I really get lost on a lot of those specification tables.

 

I was the one who wrote this data sheet including the section explaining how and why the caps are essential to make it stable.

Imagine how happy I would be if someone..... anyone.... would actually read it.

Bountyhunter

Are the regulators with dual part numbers better on the oscillation issue? For example, I have seen these chips (5.0 version) that are also marked "7805"

 

I read it bountyhunter. It was wonderful

Thank you.

That'll be five cents please.....

 

Yes, even the parts I don't understand were written beautifully.

That's the signature hallmark of my technical writing....

 

Bountyhunter

Are the regulators with dual part numbers better on the oscillation issue? For example, I have seen these chips (5.0 version) that are also marked "7805"

Interesting question..... I also happen to have re-written the Nat Semi data sheets that applied to the LM78XX and LM79XX series..... but I was integrating them together with the national parts which were the LM320/340 regulator series. I have seen many parts "dual marked" with LM340-X.X and LM78X.X but I never saw a part dual marked between the 78xx and the 294X series. They are actually very different parts similar in function, but completely different in performance and stability.

The 78XX series were invented and created by fairchild, and NSC responded with the LM340 series which was nearly identical..... eventually, fairchild went out of business and NSC decided to make both the 340 and 78XX lines (seperately marked) but using the same die. Eventually, the 78XX and 340 were "integrated" together on the data sheet and were dual marked.

The LM2940 was the first low dropout regulator ever made at NSC and it was an automotive group design..... I might be unkind and say that explains it's poor performance and pre disposition to oscillate.


Here is the "dual" data sheet for LM78XX/340 now published by TI (who bought Nat Semi):

http://www.ti.com/lit/ds/symlink/lm340-n.pdf

The LM2940 is a different part:

http://www.ti.com/lit/ds/symlink/lm2940-n.pdf

 

Interesting question..... I also happen to have re-written the Nat Semi data sheets that applied to the LM78XX and LM79XX series..... but I was integrating them together with the national parts which were the LM320/340 regulator series. I have seen many parts "dual marked" with LM340-X.X and LM78X.X but I never saw a part dual marked between the 78xx and the 294X series. They are actually very different parts similar in function, but completely different in performance and stability.

The 78XX series were invented and created by fairchild, and NSC responded with the LM340 series which was nearly identical..... eventually, fairchild went out of business and NSC decided to make both the 340 and 78XX lines (seperately marked) but using the same die. Eventually, the 78XX and 340 were "integrated" together on the data sheet and were dual marked.

The LM2940 was the first low dropout regulator ever made at NSC and it was an automotive group design..... I might be unkind and say that explains it's poor performance and pre disposition to oscillate.

Ok, thanks for the long and excellent explanation. You made me get off of my duff and walk down to check the part. You are absolutely right and I mis-remembered. The parts I have are 340/78xx. I always wanted to know why they were dual marked but sorry for the mistaken part number.

 

Ok, thanks for the long and excellent explanation. You made me get off of my duff and walk down to check the part. You are absolutely right and I mis-remembered. The parts I have are 340/78xx. I always wanted to know why they were dual marked but sorry for the mistaken part number.

The dual marking was NSC eventually admitting they were the same part (which many people had known for years). The 78XX had "market name recognition" far beyond the LM340 so NSC made both parts to take advantage of fairchild's market share under 78XX... but eventually got tired of building, marking and stocking the same part under two different part numbers. Another example of the lunatics running the asylum.

 

I was the one who wrote this data sheet including the section explaining how and why the caps are essential to make it stable.

Imagine how happy I would be if someone..... anyone.... would actually read it.

Being publicly smacked by the guy who actually wrote the datasheet?

Priceless!

 

Thank you guys for solving my problem, I am sorry I didn't put the full part number.