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

Abstract

A semiconductor memory device using system clock with a high frequency can maintain a constant operation margin even in the change of operation environments including voltage level, temperature, and process. The semiconductor memory device includes an output control signal generator configured to be responsive to a read pulse that is activated in response to a read command, to generate an odd number of first output source signals corresponding to a rising edge of a system clock and a even number of second output source signals corresponding to a falling edge of the system clock, and an output enable signal generator configured to generate a first rising enable signal and a falling enable signal on the basis of the first output source signal and generate a second rising enable signal on the basis of the second output source signal, according to column address strobe (CAS) latencies, the first rising enable signal being activated earlier than the second rising enable signal by a half cycle of the system clock.