A wakeup circuit includes an amplification stage circuit and a filter stage circuit. The amplification stage circuit is configured to, in response to receiving an input signal, generate an amplified digital signal that is proportional to the input signal. The filter stage circuit is configured to, in response to receiving a threshold number of toggles of the amplified digital signal within a pre-defined time period (such as one clock period of a clock signal), generate a wakeup signal as an output signal of the filter stage circuit.