1.8-V 800-Mb/s/pin DDR2 and 2.5-V 400-Mb/s/pin DDR1 compatibly designed 1Gb SDRAM with dual clock input latch scheme and hybrid multi-oxide output buffer

Two circuit techniques of DDR1/DDR2 compatible chip architecture designed for both high-speed and high-density DRAMs are presented. The dual clock input latch scheme, which reduces the excessive timing margin for random input commands by using a pair of latch circuits controlled by dual-phase 1-shot clock signals, achieves a 0.9-ns reduction in cycle time from 3.05 ns to 2.15 ns. By using these techniques in combination with a hybrid multi-oxide output buffer, we developed a 175.3 mm² 1Gb SDRAM which operates as a 800-Mb/s/pin DDR2 or 400Mb/s/pin DDR1.