I have some Lolin32 Lite boards which work off a 18650 battery. These batteries generally deliver 3.2V to 4.2V.
I think that the voltage is regulated through an AMS1117 3.3V.
What confuses me is is that the data sheets say that the dropout voltage for the AMS1117 is typically 1.1V. Therefore, to get 3.3V out, you would need at least 4.4V in. Which is greater than a fully charged 18650.
It apears that it shouldnt work, but it does.
Can anybody explain why it works?
An ESP32 has a typical minimum operating volts of 2.3V.
When I test the 3.3V output pin on the board though, it is reading just slightly under 3.3V.
And the battery voltage is down to 3.5V.
The dropout of the regulator will be smaller when the current drawn is lower. That 1.1V "low" dropout will be at the maximum rated current.
There are regulators with truly low dropout, such as mcp1700-33, ht7333, but they have a lower input voltage range and a lower maximum current, so choose carefully.
Thanks for that.
So it may become more significant if you have a few periferals powered by the board.
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