An 8.4Gb/s 2.5pJ/b mobile memory I/O interface using simultaneous bidirectional Dual (Base+RF) band signaling

Abstract

Power and bandwidth requirements have become more stringent for DRAMs in recent years. This is largely because mobile devices (such as smart phones) are more intensively relying on the use of graphics. Current DDR memory I/Os operate at 5Gb/s with a power efficiency of 17.4mW/Gb/s (i.e., 17.4pJ/b)[1], and graphic DRAM I/Os operate at 7Gb/s/pin [3] with a power efficiency worse than that of DDR. High-speed serial links [5], with a better power efficiency of ∼1mW/Gb/s, would be favored for mobile memory I/O interface. However, serial links typically require long initialization time (∼1000 clock cycles), and do not meet mobile DRAM I/O requirements for fast switching between active, standby, self-refresh and power-down operation modes [4]. Also, traditional baseband-only (or BB-only) signaling tends to consume power super-linearly [4] for extended bandwidth due to the need of power hungry pre-emphasis, and equalization circuits.