I recently bought an AUK S1117-33PI 3.3V voltage regulator. Unfortunately, I don't have a proper bench top power supply, so i used a basic travel adapter ,whose output is 5V - 1A, just to test the voltage regulator out. The voltage regulator gave a perfect 3.3V out but it got really hot after keeping it on for about 20 - 25 seconds. I later checked the current draw from the travel adapter and found that the voltage regulator was consuming a constant 0.5A with no load attached.

It might as well obviously occur to most of you guys that the chip is probably a bad one but i want to take my chances and find out any other wild guesses.

Thanks in advance...

  • 1
    \$\begingroup\$ Did you definitely connect it the right way round? \$\endgroup\$
    – David
    Jul 13, 2016 at 22:39
  • \$\begingroup\$ Yes! definitely. \$\endgroup\$ Jul 13, 2016 at 22:41
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    \$\begingroup\$ What did you have on it for caps? \$\endgroup\$ Jul 13, 2016 at 23:00

1 Answer 1


That chip is broken or wired up incorrectly – the datasheet says the quiescent current should be below 10mA.

  • \$\begingroup\$ Or there's some sort of oscillation going on due to high input impedance or something like that. Maybe needs more input capacitance. Though broken is still a good guess. \$\endgroup\$
    – John D
    Jul 13, 2016 at 22:56
  • \$\begingroup\$ Isn't it unlikely that a linear regulator would tend to oscillate that much? however, that would still be covered by "wired up incorrectly". \$\endgroup\$ Jul 13, 2016 at 23:30
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    \$\begingroup\$ @KushalKumar what did you think? \$\endgroup\$ Jul 13, 2016 at 23:34
  • \$\begingroup\$ Well, there is a graph in the data sheet showing that you need a certain range of ESR for stability with ceramic caps. Seems pretty forgiving but if the caps didn't meet the criterion you could get oscillation that could draw substantial current. Of course that could still be considered "wired up incorrectly". \$\endgroup\$
    – John D
    Jul 14, 2016 at 2:17
  • \$\begingroup\$ @JohnD um, might be blind today: where in the datasheet? \$\endgroup\$ Jul 14, 2016 at 8:43

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