When setting the output voltage for the regulator, what voltages should appear at FB1 and FB2?
When the system is in regulation, the feedback pins FB1 and FB2 will be at the bandgap reference voltage (1.238V typical). This may not be obvious from the datasheet, since only the bandgap reference voltage is specified. But if you look at the block diagram, it shows that one input of the gm error amplifier is the FB pin (for output feedback), and the other is the bandgap reference voltage BG; the error amplifier”s role is to make sure its inputs are at the same voltage.
