A memory device including a plurality of pins and a plurality of memory dies is provided. Each of the memory dies is coupled to the pins, and each of the memory dies includes a matching circuit and a core circuit. During a course of power-on, according to voltage levels of data pins or control pins, the matching circuit may be selected automatically an enabled one of memory dies. When the core enabling signal is enabled, the core circuit starts operating, and when the core enabling signal is disabled, the core circuit stops operating. When the core circuit of one of the memory dies is operating, the core circuits of the rest of the memory dies stop operating.