Data output control circuit of a double data rate (ddr) synchronous semiconductor memory device responsive to a delay locked loop (dll) clock

Abstract

A semiconductor memory device using system clock with a high frequency can maintain a constant margin of operation even with a changed operating environment including voltage level, temperature, and process. The semiconductor memory device includes a data output control circuit configured to control data outputted in synchronization with a falling edge of a system clock using a first output source signal corresponding to a rising edge of the system clock, and to control data outputted in synchronization with the rising edge of the system clock using a second output source signal corresponding to a falling edge of the system clock, and a data output circuit configured to output data, the data output circuit being controlled by the data output control circuit.