At 12:33 PM 4/25/03 -0500, Picdude wrote: >Neil, > >This is interesting, and very important to me, as I usually pick up 7812's >based on whatever's available and low-cost. I have a ckt here feeding a 7812 >from 14.2V, and can't see which mfgr the part is from. I've got 3 diff >datasheets from National, Fairchild and TI, all which claim to be 2V. > >Can you please tell me which mfgr claims 3V? It's important to me, so that I >can avoid that one. If I had to raise the input to >15V, at almost 1A, that >would generate a lot more heat. I have not yet seen ANY supplier guarantee a 2V dropout for ANY 78xx regulator. As always, the data sheet remains the final authority. I quoted page numbers from the NS datasheet in my previous message. You mention Fairchild - the closest data sheet I see is for a KA78xx. Looking at page 7 of that data sheet shows that the minimum input voltage for a KA7812 is 14.5V. If your circuit can fail in a spectacular fashion because the regulator dropped out of regulation, you may wish to select a different device. However, its probably fine the way it is. How much ripple is present on the input to the regulator? Will that ripple affect your circuit if the regulator does drop out of regulation? What happens if the 12V regulated supply drops down to 11.5V? If nothing bad happens with any of the above scenarios, don't worry about it. dwayne -- Dwayne Reid Trinity Electronics Systems Ltd Edmonton, AB, CANADA (780) 489-3199 voice (780) 487-6397 fax Celebrating 19 years of Engineering Innovation (1984 - 2003) .-. .-. .-. .-. .-. .-. .-. .-. .-. .- `-' `-' `-' `-' `-' `-' `-' `-' `-' Do NOT send unsolicited commercial email to this email address. This message neither grants consent to receive unsolicited commercial email nor is intended to solicit commercial email. -- http://www.piclist.com#nomail Going offline? Don't AutoReply us! email listserv@mitvma.mit.edu with SET PICList DIGEST in the body