Post by thread:[EE]: 7912/7905

whats the pinout of a 7905 and 7912? They are negative voltage regulators. I think they are like this looking at front(not tabbed side) Input Gnd Output Andy N1YEW -- http://www.piclist.com hint: PICList Posts must start with ONE topic: [PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads

I've always wondered if this was so the 79xx series parts wouldn't be damaged if you put them into a 78xx series circuit (the input would be negative wrt the GND terminal, and the regulator would just try to keep the output at V+ minus the rated voltage). Is this why? Any thoughts? Sean At 09:41 AM 3/9/01 +0530, Anand Dhuru wrote: >No Andy, thats how the positive regulators (78XX) are pinned; the 79XX parts >are Gnd-Inp-Out > >Regards, > >Anand > >{Original Message removed}

That's because there is an internal protection diode between in and out. Vasile On Fri, 9 Mar 2001, Sean H. Breheny wrote: {Quote hidden}> I've always wondered if this was so the 79xx series parts wouldn't be > damaged if you put them into a 78xx series circuit (the input would be > negative wrt the GND terminal, and the regulator would just try to keep the > output at V+ minus the rated voltage). > > Is this why? Any thoughts? > > Sean > > At 09:41 AM 3/9/01 +0530, Anand Dhuru wrote: > >No Andy, thats how the positive regulators (78XX) are pinned; the 79XX parts > >are Gnd-Inp-Out > > > >Regards, > > > >Anand > > > >{Original Message removed}

At 03:06 AM 3/9/01 -0500, you wrote: >I've always wondered if this was so the 79xx series parts wouldn't be >damaged if you put them into a 78xx series circuit (the input would be >negative wrt the GND terminal, and the regulator would just try to keep the >output at V+ minus the rated voltage). > >Is this why? Any thoughts? The die is bonded to the heatsink tab, which should be the most *negative* point. That's ground on the 78xx and input on the 78xx. Best regards, =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-= Spehro Pefhany --"it's the network..." "The Journey is the reward" spam_OUTspeffTakeThisOuTinterlog.com Info for manufacturers: http://www.trexon.com Embedded software/hardware/analog Info for designers: http://www.speff.com Contributions invited->The AVR-gcc FAQ is at: http://www.bluecollarlinux.com =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-= -- http://www.piclist.com hint: The list server can filter out subtopics (like ads or off topics) for you. See http://www.piclist.com/#topics

At 03:06 AM 3/9/01 -0500, you wrote: *negative* point. That's ground on the 78xx and input on the 78xx. ^^^^ <cough> 79xx Best regards, =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-= Spehro Pefhany --"it's the network..." "The Journey is the reward" .....speffKILLspam@spam@interlog.com Info for manufacturers: http://www.trexon.com Embedded software/hardware/analog Info for designers: http://www.speff.com Contributions invited->The AVR-gcc FAQ is at: http://www.bluecollarlinux.com =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-= -- http://www.piclist.com hint: The list server can filter out subtopics (like ads or off topics) for you. See http://www.piclist.com/#topics

>Input Gnd Output definitely not. One end is ground. These are not a 7800 series device with pnp transistors in place of npn. It still uses npn transistors inside and the pin functions are adjusted to suit. It does mean you have to insulate the tab if mounting it to a grounded heatsink. I cannot tell you the pinout off hand, but I know the above from my first use of 7900 series devices. -- http://www.piclist.com hint: The list server can filter out subtopics (like ads or off topics) for you. See http://www.piclist.com/#topics

-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 Don't know for sure, but you could probably find a datasheet at http://www.national.com - -Randy Glenn This coming from the guy with a system tray 10 icons wide... by 2 tall... yes, I am insane ;) ================================================= Randy_Glenn-at-tvo.org - PICxpert-at-picxpert.com PICxpert-at-yahoo.com - PICxpert-at-home.com http://www.picxpert.com/ ================================================= - {Original Message removed}