I am trying to choose a voltage regulator. One of the metrics I keep seeing is output current, e.g. "Output current up to 800 mA".

Does that mean the sum of current that the rest of my circuit draws, and is connected to the regulator supply, has be to < 800 mA? E.g. if I have (these are mostly made up):

  • MCU at 50 mA
  • sensor at 20 mA
  • LCD screen at 100 mA
  • bluetooth chip at 40 mA
  • memory module at 60 mA

Then my output current from the regulator, which is powering all these, has to be at least 270 mA (= 50 + 20 + 100 + 40 + 60)?


The "maximum output current" spec for a voltage regulator is indeed the maximum current it can deliver to a load (with an appropriate heatsink,and due consideration for the power loss due to the input/output voltage differential).

  • \$\begingroup\$ So to confirm a simple electronics fact, my "load" would be the sum of all the current consumed by the parts I mentioned in my example? \$\endgroup\$ – JDS Jun 24 '14 at 1:55
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    \$\begingroup\$ Your current load, yes. \$\endgroup\$ – sherrellbc Jun 24 '14 at 2:14
  • \$\begingroup\$ Alright cool, looks like we're all done here. Thanks guys. \$\endgroup\$ – JDS Jun 24 '14 at 2:19
  • \$\begingroup\$ That your load is less than the maximum is a necessary, but not sufficient, condition. Usually linear regulators are limited by the temperature rise for steady loads, as Peter said \$\endgroup\$ – Spehro Pefhany Jun 24 '14 at 4:08
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    \$\begingroup\$ Not just high ambient. Just as an example TLV1117 rated 800mA, Say θja is 50°C/W, Ta = 30°C (not hot). Input 12V output 5V, at only 200mA Tj will be 100°C (70°C rise). This must be calculated for the situation. \$\endgroup\$ – Spehro Pefhany Jun 24 '14 at 14:39

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