I have two LDOs that convert different input voltages into the same voltage. I'm not sure how to safely connect the outputs together so they become the same signal and can be both be used to power the board, is it as simple as just connecting the outputs together since the voltage is the same? Thanks

  • \$\begingroup\$ You probably should not connect the outputs, directly. What are the two input voltages, which you say are different? \$\endgroup\$ – jonk Dec 6 '18 at 1:26

It is not at all recommended to parallel the output of the two LDOs together. The one with the higher voltage output will try to supply the load - that is if you can keep them stable and not get oscillation happening.

A better method will be to use one LDO and diode OR the input sources into the LDO. Then the higher voltage supply will contribute.

  • \$\begingroup\$ Thanks! Reading up on it sounds like exactly what I needed. \$\endgroup\$ – Johnny Dec 6 '18 at 1:29
  • \$\begingroup\$ @Johnny - Yeah. Should work out OK. Use Shottky type diodes if you want to limit the voltage drop across the diodes. Nice thing however is that putting the diodes in front of the LDO means that you can get a nice regulated voltage out at your load. That is compared to if you tried to diode-OR a two LDO solution together where the diode drops would mess with your regulated voltage levels. \$\endgroup\$ – Michael Karas Dec 6 '18 at 2:40

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