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In the process of fault finding a circuit I am building using an ESP8266, I think I found the problem may be with my LM1117-3,3.

The circuit starts off fine drawing between 80 (off state) and 160 (on state) mA. I measure this via 10 10ohm resistors in parallel. I.E. through a 1ohm shunt resistor.

The strange thing is that the current keeps rising until the LM1117-3,3 goes into shutdown mode (Thermal I think). I tested the LM1117-3,3 through 1K1ohm resistor (Static resistor) and it starts off at the calculated 3mA but just keeps climbing.

The output voltage remains stable to the end, so no idea where all the extra current is going.

I have a 10uF cap between input and GND and a 100uF cap between output and gnd just like it states in the datasheet. Input voltage is 5.12V via a 2A capable plug pack.

Is this a faulty regulator?

Update
Circuit diagram tested above.

schematic

simulate this circuit – Schematic created using CircuitLab

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    \$\begingroup\$ do you have a schematic of your circuit? \$\endgroup\$
    – helloworld922
    Commented Sep 4, 2016 at 6:38
  • \$\begingroup\$ Just noting that in my experience of ESP8266, it draws more like 300mA when active, which may or may not be relevant. \$\endgroup\$
    – Roger Rowland
    Commented Sep 4, 2016 at 6:56
  • \$\begingroup\$ Measure the output current too. \$\endgroup\$
    – winny
    Commented Sep 4, 2016 at 7:14
  • \$\begingroup\$ @RogerRowland: In this circuit it is drawing 82mA relatively constantly. \$\endgroup\$
    – Gineer
    Commented Sep 4, 2016 at 8:17
  • \$\begingroup\$ @winny Output current for the test circuit is 3.amA and remains constant. \$\endgroup\$
    – Gineer
    Commented Sep 4, 2016 at 8:18

1 Answer 1

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Without a schematic it is hard to offer too much in the way of suggestions. That said I would recommend that you take a careful look at your 100uF output capacitor. Check to see if you have it oriented properly in the circuit because if it is a polarized unit that is in backwards it could be the source of the problem.

Be careful too. Some types of reversed capacitors can be rather dangerous. Aluminum electrolytic types can explode out of their can if they get too hot. Tantalum types can burst into flame.

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  • \$\begingroup\$ I think this was my issue. Sorting out the booting problem with the ESP8266 completely distracted me from the basics. Luckily my tantalum just got hot and didn't actually burst into flames. \$\endgroup\$
    – Gineer
    Commented Sep 4, 2016 at 8:22
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    \$\begingroup\$ You may have been saved from the flames because you used a current limited power source. \$\endgroup\$
    – Michael Karas
    Commented Sep 4, 2016 at 8:34

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