Provided are an input buffer of a memory device, a memory controller, and a memory system making use thereof. The input buffer of a memory device is enabled or disabled in response to a first signal showing chip selection information and a second signal showing power down information, and the input buffer is enabled only when the second signal shows a non-power down mode and the first signal shows a chip selection state. The input buffer is at least one selected from the group consisting of a row address strobe input buffer, a column address strobe input buffer, and an address input buffer.