Provided are a circuit and method for sampling a valid command using a valid address window extended for a high-speed operation in a double pumped address scheme memory device. A method for extending the valid address window includes: inputting a valid command signal and a first address signal at the first cycle of a clock signal; inputting a second address signal at the second cycle of the clock signal; generating a decoded command signal and extended first and second internal address signals respectively in response to the command signal and the address signals; and latching and decoding the extended first and second internal address signals in response to the decoded command signal.