US Patent 7646656 Semiconductor memory device

A semiconductor memory device includes: an input pad set configured to receive an external input signal and a reference voltage; an input buffer set configured to detect and transmit the input signal to an internal circuit of the semiconductor memory device by comparing the input signal with the reference voltage; and a reference voltage generation circuit configured to generate the reference voltage to supply the reference voltage to the input pad set and the input buffer set during a test operation, the reference voltage generation circuit being deactivated after the semiconductor memory device is packaged.