Arduino pro mini voltage regulator

Projects General Guidance
1

Hello

I require a current of about 300mA for my project using the mini.

The datasheet for the arduino pro mini regulator states 320mA current limit? Why does the Arduino schematic state 150mA?

If it is 150mA, I am going to install an external regulator and feed the mini via the VCC input pin.

However, I need the regulator to have very low Quiescent current to minimize battery consumption.

Can anyone recommend one? Does anyone foresee any issues with this solution?

2

I am not sure as to why the the datasheet states that however if you are looking for power control the first thing we would need to know is how you plan to source your input power.

WHY?
Conversion efficiency!

Here are my assumptions:
You are mentioned a battery so I am assuming you are using a 9V battery.
Secondly I am going to assume you are designing for 350mA. (best to give yourself some margin)

Here is what I would recommend:

  • Think about the POWER dissipated If you are going to be using a Linear for this you will be converting the Voltage down via burning off the excess energy. Now IDK which version you have the 5 or 3.3V variant but the example stand either way. Think about this 9V-5V = 4V and P= V*I therefore we have 4V *0.350mA = 1.4W which upon looking at the datasheet of the regulator shows a thermal resistance of 220 C/W which means when this thing is going at full load you will have to get sink 308 Degrees C So as you can see efficiency matters!!! If you to plan to go the LDO route take a look at the TPS series of LDOs from TI...they have lower thermal resistances
  • What about Switching???? Ok so its not as simple as an LDO but with a switcher you can easily get north of 80% efficiency and easily meet any of the load requirements that you stated. TI has many simple Switchers that make your life really easy especially with their online design tools. My recommendation would be to use the LMR16006 simple switcher controller or a similar simple switcher module and then finish up the design within their webench tool.

I hope that helps!

3

spaceuino:
The datasheet for the Arduino pro mini regulator states 320mA current limit? Why does the Arduino schematic state 150mA?

Neither of these is in any way relevant to the Pro Mini.

You cannot power a UNO, Nano or Pro Mini via the on-board regulator if you need to draw any significant current (say, over 60 mA) from the "5V" terminal or from any combination of this and I/O pins.

Why?

Because it does not have a heatsink! So whatever rating it has in the datasheet, relating to such regulator with a proper heatsink fitted, is simply irrelevant.

It is up to you to determine the pros and cons of LDO linear or switchmode regulators.

4

The datasheet you point to is titled: "150 mA Low-Noise LDO Regulator". I don't see anywhere in the datasheet where it says 350 mA. The only '350' is a 350 milliVOLT dropout voltage at a 150 mA load current and wide temperature range (–40°C < TJ < +125°C).