ESP8266 Community Forum

- Mon Jun 08, 2015 3:23 pm #19862 In this case any unused pins I would leave floating because they are GPIO pins and undetermined states aren't going to impact the chip's function.

I just noticed that you've written your input power source to be 12V. There's a few things wrong here:

• I don't see a bulk cap on the input. LDO regulators almost always want some input capacitance for stability, 10uF is enough here
• You're indicating a 12V input but with a 3.3V output the regulator is going to have to dissipate a lot of heat. P=VI=(12-3.3)*0.2=1.74W. You indicated a part in a SOT-223 which can't dissipate a lot of heat.
• The biggest problem is that the IRU1117CY is only rated for a maximum 7V input

If you want to use the IRU1117CY then I would limit the input voltage to 5V and also use a reverse voltage protection diode which will not only protect against reversed polarity but it will help dissipate some of the heat and reduce the power loss in the LDO.

- Mon Jun 08, 2015 4:26 pm #19871 Oh I was actually using the LT 1117 for my tests. The IRU1117CY was just a placeholder because my program had no schematics for the LT 1117. It gets pretty hot but is working fine... have to do some more long time testing I guess. I think with some bigger copper areas nearby it should work. Anyways in this case it's just a placeholder for any 3.3V converter. I will delete the name of the component.

A reverse voltage protection diode would be a good idea anyways. I'll add that.

- Tue Jun 09, 2015 2:55 am #19905 For anything above ~100 mA I'd recommend a buck converter instead of a lineair regulator. They're dead cheap now and very small as well. They generally can convert from ~30 V to ~2.5 V on 2000-3000 mA without getting quite warm, so that means they're much more efficient. Converting from 12 V to 3.3 V using a lineair regulator is like inserting a big resistor and a small transistor to handle the transients, and this big resistor is going to burn a lot of power continuously.

- Tue Jun 09, 2015 8:55 am #19927 I think your cap on Reset line is backwards.