A Low-Power Multi-Phase Oscillator with Transfer Gate Phase Coupler Enabling Even-Numbered Phase Output

We propose a transfer gate phase coupler for a low-power multi-phase oscillator (MPOSC). The phase coupler is an nMOS transfer gate, which does not waste charge to the ground and thus achieves low power. The proposed MPOSC can set the number of outputs to an arbitrary number. The test circuit in a 180-nm process and a 65-nm process exhibits 20 phases, including 90◦ different angles. The designs in a 180nm CMOS process and a 65-nm CMOS process were fabricated to confirm its process scalability; in the respective designs, we observed 36.6% and 38.3% improvements in a power-delay products, compared with the conventional MPOSCs using inverters and nMOS latches. In a 65-nm process, the measured DNL and 3σ period jitter are, respectively, less than ±1.22◦ and 5.82 ps. The power is 284 μW at 1.85 GHz. key words: multi-phase oscillator, transfer gate phase coupler, evennumbered phases, low-power, process scalable