The invention relates to an electronic device that includes a wake-up system that operates at a substantially low power level and is applied to wake up the electronic device from a sleep mode. The wake-up system comprises a sound transducer that converts a received sound signal to an electrical signal and a keyword detection logic that preliminarily identifies a speech energy profile that corresponds to at least one of a plurality of keywords in a part of the electrical signal. In some embodiments, a keyword finder is further activated to identify with an enhanced accuracy whether the at least one keyword exists in the part of the electrical signal, and generates a wake-up control to activate a host of the electronic device from its sleep mode.