A 0.45 pJ/b, 6.4 Gb/s Forwarded-Clock Receiver With DLL-Based Self-Tracking Loop for Unmatched Memory Interfaces

Abstract

This brief presents a power- and area-efficient forwarded-clock (FC) receiver with a delay-locked loop (DLL)-based self-tracking loop for unmatched memory interfaces. In the proposed FC receiver, the self-tracking loop is composed of two-stage cascaded DLLs to support a burst mode. The proposed scheme compensates for a delay drift neither by relying on data (DQ) transitions nor by re-training but with a write training of the memory controller to fine-tune a data strobe (DQS) path delay through DLLs. The proposed FC receiver is fabricated in the 65-nm CMOS technology and the active area including 4 DQ lanes is 0.0329 mm2. After the write training is completed at supply voltage of 1 V, the measured timing margin remains larger than 0.31 UI when the supply voltage drifts in the range of 0.94 V and 1.06 V from the training voltage, 1 V. At the data rate of 6.4 Gb/s, the proposed FC receiver achieves an energy efficiency of 0.45 pJ/bit.