I would like to design a circuit which has outputs LOW when the voltage it is connected to is below a threshold, like 3.3V.
There are some ic's you can buy to do this, but I would like to make my own so I can tweak the detection voltage for each specific application. From looking at the datasheets for these chips, it looks like they create a reference voltage and then use a comparator to compare the input to the reference, then that drives a transistor. Does that seem correct? Sorry if this is very simple, I am a noob :)
Example IC by microchip: http://ww1.microchip.com/downloads/en/DeviceDoc/20001434K.pdf
Another example by ST: https://docs-emea.rs-online.com/webdocs/135f/0900766b8135f981.pdf
I don't need a very accurate device, the threshold voltage can vary quite a lot for my application. I found a voltage reference which is quite cheap and might be suitable, but I guess the reference voltage needs to be lower than the input voltage will ever be.