Voltage regulator with alternate voltage source...
wdonzelli at gmail.com
Thu Apr 7 16:03:54 CDT 2016
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:
> Err.. unless the voltage of the switcher is identical to that of the 7805,
> then one device will source current, and the other will sink it.
> Like putting two 6V batteries in parallel, where one is fresh and the other
> weak. Current will flow until the potentials are equalized. But with two
> regulated circuits, I don't see how equality can be achieved.
> Not saying it's going to smoke-out, but it does seem like a wonky thing to
> On Thu, Apr 7, 2016 at 3:41 PM, wulfman <wulfman at wulfman.com> wrote:
>> You should be just fine.
>> On 4/7/2016 1:38 PM, Bill Sudbrink wrote:
>> > If you have a circuit which is normally designed to
>> > operate with an unregulated supply, through a regulator...
>> > say unregulated +8 through a 7805 to a regulated +5 and
>> > you want to test it independent of the +8 supply, if
>> > you leave the unregulated rail unattached and put +5
>> > switcher straight onto the regulated +5 rail, will you
>> > damage the 7805? Clearly the VIN is open, but the ground
>> > pin will still be attached. Would this push voltage
>> > back through and screw things up?
>> > Thanks,
>> > Bill S.
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