A 1.8-v 700-Mb/s/pin 512-Mb DDR-II SDRAM with on-die termination and off-chip driver calibration

A 512-Mb DDR-II SDRAM has achieved 700-Mb/s/pin operation at 1.8-V supply voltage with 0.12-mum DRAM process. The low supply voltage presents challenges in high data rate and signal integrity. Circuit techniques such as hierarchical I/O lines, local sense amplifier, and fully shielded data lines without area penalty have provided improved data access time and, thus, high data rate can be achieved. Off-chip driver with calibrated strength and on-die termination are utilized to give sufficient signal integrity for over 533-Mb/s/pin operation.