In case some of you are using Li-Ion batteries for powering circuits, this one is for you!
UVLO is short for UnderVoltage Lock-Out and means that when the voltage of the battery is too low, it shuts everything down, protecting it from falling too low. This circuit is protecting your Li-Ion from deep discharge.
Following a schematic from Analog Devices “Technical Articles”. There are a muriad of different interesting circuits, so feel free to browse through them.
This circuit uses two components from Analog Devices: the voltage reference LT1389 and the comparator LT1495. Both are designed for very low power consuption.
And this circuit functions as follows:
The comparatos is wired as Schmitt-Trigger (R5 is doing the feedforward), which at 3V turns off the MOSFET SW1. Since the voltage of the Li-Ion is rising a bit at shutoff the hysteresis is essential. In this case the upper hysteresis level is at 3.092V.
If you click at the link below the schematic there are all calculations and even more explanations.
As I said, the circuit is designed for low power consumption. The whole thing only needs about 4.5µA. So even if the Li-Ion is discharged it is not really draining any more power from it, further protecting the Li-Ion cell.
In a nutshell:
This circuit protects your battery cells from deep discharge. The circuit itself is very small and doesn’t take much space on the PCB. Definitely consider using this if you are working with Li-Ion cells.