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A near-threshold forwarded-clock I/O receiver architecture is presented. In the proposed receiver, the majority of the circuitry is designed to operate in the near-threshold region at 0.6 V supply to save power, with the exception of only the global clock buffer, test buffers and synthesized digital circuits at the nominal 1 V supply. To ensure the quantizers are working properly with this low supply, a 1:10 direct demultiplexing rate is chosen as a demonstration of achieving low supply operation by high-parallelism. A novel low-power super-harmonic injection-locked ring oscillator is proposed to generate deskewable symmetric multi-phase local clock phases. The relative performance impact of including a per-data lane sample-and-hold (S/H) to improve quantizer aperture time at low voltage is demonstrated with two receiver prototypes fabricated in a 65 nm CMOS technology. Including the amortized power of global clock distribution, the receiver without S/H consumes 1.3 mW and the one with S/H consumes 2 mW at an 8 Gb/s input data rate, which converts to 0.163 pJ/bit and 0.25 pJ/bit, respectively. Measurement results show both receivers get BER <; 10-12 across a 20-cm FR4 PCB channel.
Date of Publication: Aug. 2012