Two supplies...actually. That as an example. Two supplies, one off the wall, one from a UPS. Both identical switching supplies, but due to a cable length, one supply may be at a lower potential than the other by around a volt or two. The grounds are all tied together on the board. They shouldnt fight each other due to the diode..I think. In the past where I tied multiple supplies to a single power plane/bus bar system, the outputs of each were diode or'ed but they were all at the same output voltage. --- On Thu, 4/9/09, Vitaliy wrote: > From: Vitaliy > Subject: Re: [EE] Diode ORing supplies > To: "Microcontroller discussion list - Public." > Date: Thursday, April 9, 2009, 9:46 AM > alan smith wrote: > > Typically if you have two power sources, you diode OR > them, so they will > > not backfeed to each other. Application is battery > backed systems, etc. > > > > If you have one supply, say the battery sitting on a > trickle charger, and > > aother wall supply, both feeding a power plane,and if > one supply is at a > > slightly higher potential, > > So you basically have THREE power supplies, all feeding the > same circuit? > Trickle charger, battery, and the wall supply? > > And the "ground" levels of the trickle charger > and the wall supply, are > slightly different? So like, the trickle charger's Gnd > is at 0V, and the > wall supply's Gnd is at +0.5V? > > > > ..will it draw more current from the lower potential > supply in order to > > normalize the voltage on the plane? > > Either I don't understand the question, or the question > is wrong. The power > supplies will be fighting each other, so they will both be > supplying more > current than is required by the circuit. > > Vitaliy > > -- > http://www.piclist.com PIC/SX FAQ & list archive > View/change your membership options at > http://mailman.mit.edu/mailman/listinfo/piclist -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist