so im trying to assemble a circuit to take my 120VAC wall line and ultimately power a small smart hub, small transformer i found somewhere that was actually labeled with which pins were input/output, 110VAC yields 11.7VAC, but because its a cheap transformer its putting out 21v unloaded, which is way higher than an 1117 can take, so i went looking at what else i had. find an old 1084 regulator i looked at the datasheet and instead of listing a maximum input voltage, it lists "Maximum Input to Output Voltage Differential" as 27V. so if the max differential is 27v, and the output is (to simplify math) 3v, my max input is 30v, correct?
for the sake of my understanding, would the component be able to take input floating between 30 and 40 VDC, and with the proper voltage divider on the adjustment pin, regulate to 24v?
lastly, is this unique to this device or is this just how voltage regulators worked and i never understood?