Quote:
Originally Posted by audioguru  This is from the latest datasheet for Texas Instruments uA7800 series regulators: |
Sometimes one guy will make a second source that deviates from industry standard specs. I know the original spec was 35 because I did the data sheets at Fairchild and later at NSC. Fairchild originated the 78XX family, NSC later second sourced it with a part family called the LM340-XX. The problem was the 78XX was already industry standard so NSC altered their data sheets to match the 78XX specs. If that wasn't enough, they eventually marked all their parts with both part numbers (LM340-XX and LM78XX) to make sure the parts were universally recognized. At one point, the data sheet also carried both numbers.
I don't know why TI dropped the spec but I'll wager it's because their process wasn't capable of making the 35V breakdown spec so they just changed their data sheet hoping most people wouldn't care. And most won't because the the world keeps going to lower and lower voltages. The 78XX series in general is obsolete and doesn't run much volume any more compared to the newer stuff. It also has razor thin profit margins which is why the product lines at NSC kept kicking them to other departments because nobody wanted them in their portfolio where they dragged down ASPs and total profit marging for the product line.
Interesting: the data sheet I put together at NSC is still there and it still shows both products specified together:
http://www.national.com/ds/LM/LM340.pdf
The abs max rating on VIN is 35V. That was the original industry standard spec for the product.
21st October 2009, 12:08 AM
Similar 
Linear Mode
