Voltage regulator with alternate voltage source...
wulfman at wulfman.com
Fri Apr 8 10:54:45 CDT 2016
http://www.ti.com/lit/ds/symlink/lm78l05.pdf ( page 8 gives you the
internals for a low power version )
Nothing in the data sheet saying you cant apply voltage to the output.
As per the low power version circuit diagram i cant see how you can do
any damage to it
I was not able to find an internal diagram for the higher power version but
i am sure its close to the same circuit just larger pass transistors.
I took a new regulator and measured the output pin to ground with my
on the diode setting and had no reading. If you think about it the
output on the regulator is a pass transistor
and the output to ground will be in effect a diode that will not allow
current to pass from output to ground.
My last comment still stands. i doubt you will cause any ill effects to
I personally have done this to some old arcade boards with no ill effects.
On 4/7/2016 6:08 PM, drlegendre . wrote:
> "...if you leave the unregulated rail _unattached_ and put +5
> switcher straight onto the regulated +5 rail..."
> My error, I read that as "attached".
> In any event, just lift both the 7805 IN and OUT pins, and then supply
> known-solid +5DC between the OUT and GND pads on the board.
> No, you can't feed the IN pin with +5V, for as others have mentioned,
> the 7805 has a minimum dropout of 2V or so.
> On Thu, Apr 7, 2016 at 4:03 PM, William Donzelli <wdonzelli at gmail.com>
>> Per his description, the 7805's input will be open. It will not try to
>> source any current, as it will have none to give.
>> I suppose there might be a little leakage.
>> On Thu, Apr 7, 2016 at 4:58 PM, drlegendre . <drlegendre at gmail.com> wrote:
The contents of this e-mail and any attachments are intended solely for the use of the named
addressee(s) and may contain confidential and/or privileged information. Any unauthorized use,
copying, disclosure, or distribution of the contents of this e-mail is strictly prohibited by
the sender and may be unlawful. If you are not the intended recipient, please notify the sender
immediately and delete this e-mail.
More information about the cctalk