Power specifications slightly off?

[amadeuspzs]

Nitpicky but wanted to share some feedback if I've understood correctly:

From https://lowpowerlab.com/guide/moteino/specifications/ it states input voltage is "3.6V-16V (up to 12V recommended)", but the MCP1703 [datasheet](https://ww1.microchip.com/downloads/en/DeviceDoc/22049f.pdf) indicates a dropout voltage of 525mV, not 330mV for 3.3V ≤ VR < 5.0V.

This would give effective (stable) input voltage as "3.8V-16V", which will only impact e.g. single LiPo cells where usable voltage is ~2.8 - 4.2V ie. you lose 0.2V of "stable" input?

[Felix]

Once you get into the dropout region the LDO starts to quiesce at a much higher current. Based on practical experience and observation this will happen around 3.6V. And the fact that it can take 16v, does not mean you should power it from 16V, in fact it's quite an unusual voltage, 12V is more common. So the 12V was more because I am trying to help people to save themselves from themselves.

The take away or TLDR; from this is:
When you walk 0m from the edge of the cliff, selfies are not a really great idea. If you walk 4m away from the cliff's edge, you can afford a selfie without too much worry.

[amadeuspzs]

Thanks Felix.

On the topic of quiescent current, my understanding of power dissipation of LDOs is that a fair bit gets released thermally.

For Vin of 12V, and Vout of 3.3V at, e.g. 8mA Iout we have a power dissipation:

Pldo = (Vin - Vout) * Iout ~ 70mW, or about 5mA equivalent draw at 12V.

At Iout of 6.5uA this gives equivalent draw of 5uA which is still double the quiescent current?

Pragmatically I'm sure this doesn't make a huge difference but wondering if a buck-boost would be better, even with the higher quiescent current and circuit complexity?

[Felix]

It ***DEPENDS***.

We'd need to start a long discussion about how, what, why, and other questions about your requirements and available power source etc.
Those are all factors that go into deciding how to power a project. A boost is almost always not a great choice, where you are worried about quiescent current. Even the most efficient boosts will end up draining the battery faster.
The Moteino has the best all around solution. It is also available in an LDO-less 8mhz variant where you can power with 3V or less and not worry about any quiescent or needing a boost solution.