Can the LP2953 auxiliary comparator input be left floating? Can this cause oscillation?
Comparator inputs should never be left floating. If not used, the input should be tied to ground. Not terminating the input could cause oscillation, depending on how noisy the environment is, as well as other things unique to the specific part (like what the impedance looking into the comparator input is). However, we do know that the input of the Auxiliary Comparator is the same circuit topology as the Shutdown input. Since the input pin is a PNP base, one would think that it would be OFF if left unconnected (since no base drive current could flow). However, all devices have some leakage current (increasing with temperature) which can turn ON this PNP. This is why it must be actively terminated to operate in a predictable manner. In summary, the Auxiliary Comparator input must be terminated (either pulled up to a fixed voltage or tied to ground) to be sure that the output is not toggling between states. Based on the operation of the Shutdown input, it is fairly certain that some devic
