a plurality of voltage divider circuits configured to divide an input signal to generate a plurality of first signals, wherein the plurality of first signals have different levels;

a plurality of front-end circuits configured to respectively sample the plurality of first signals to generate a plurality of second signals;

at least one converter circuit configured to generate at least one digital output according to the plurality of second signals and a reference voltage; and

a controller circuit configured to determine a level of the input signal according to the at least one digital output and select one of the at least one digital output according to the level of the input signal,

wherein the plurality of front-end circuits comprise a first front-end circuit and a second front-end circuit, the first front-end circuit has a first voltage detection range, the second front-end circuit has a second voltage detection range that is higher than the first voltage detection range, and a voltage resolution of the first front-end circuit is lower than a voltage resolution of the second front-end circuit.