I’m planning on purchasing the U1V10F5 step-up regulator for a project. It has an output voltage of 5V, and a minimum input voltage of 0.5V. What happens if the input voltage drops below 0.5V? Does it destroy the regulator? Does it just cause the output voltage to fall below 5V?
Because an input voltage under 0.5V is outside of the rated input range for the U1V10F5 regulator, the behavior is undefined, so there are no guarantees what it will do. That being said though, I think it is not very likely that a lower input voltage would damage the regulator. I suspect that it would just cause the output voltage to drop off.
I looked up the datasheet for the regulator used on the U1V10F5, and it has an under-voltage lockout mechanism that safely shuts the regulator down if the input voltage falls below the minimum limit.
Here’s a link to the data sheet: https://www.sparkfun.com/datasheets/Prototyping/tps61200.pdf
You are correct; I forgot about the under voltage lockout (UVLO) feature of that regulator. Please note, that the UVLO does not activate until the input drops to 0.25V, while the minimum voltage for standard operation of the TPS6120x IC is 0.3V, so there is still a small range in which the behavior of the regulator is not well defined.