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A 512 Mbit consumer DDR2 SDRAM that uses self-dynamic voltage scaling (SDVS) and adaptive design techniques is introduced in this paper. With the increase in the significance of process variation, higher performance requirements reduce the allowable design margin in DRAM circuits. However, self-dynamic voltage scaling gives a greater timing margin in the circuitry by changing the internal supply voltage in response to the operating frequency and process skew. By changing the internal supply voltage, the life time of the chip increases by more than 23 times when the supply voltage is lowered by 300 mV. The proposed adaptive design techniques include an adaptive bandwidth delay-locked loop and an adaptive clock gating. The former improves the performance by obtaining a wider valid data window and the latter saves on dynamic power consumption in the clock distribution network. The SDVS method reduces the IDD3P by 9.3% and the adaptive clock gating saves 8.8% of the IDD3N when measured at 200 MHz, 25°C The studied consumer DDR2 SDRAM was fabricated using 44 nm standard DRAM process technology. It occupies a 17.7 mm2 die area and operates using a 1.8 V power supply.
Date of Publication: Jan. 2012