A 5 pJ/pulse at 1-Gpps Pulsed Transmitter Based on Asynchronous Logic Master–Slave PLL Synthesis

This paper presents an ultralow power asynchronous logic transmitter operating at 1 Gpps that achieves pulse synthesis using a double phase-locked loop (PLL) architecture for applications exploiting large-scale neuronal interfacing with CMOS probes. The 4 GHz center frequency OOK transmitter synthesizes 500 ps duration pulses from a 31.25 MHz crystal oscillator using a cascade of a master and a slave PLL with the latter locked to the former. Both PLLs are implemented with CMOS digital cells and ring oscillator-based VCO. A prototype fabricated in a 130 nm RFCMOS process operates at a measured 5 pJ/pulse energy budget for an active area of 0.04 mm². To generate timing references and packets for high data rate recording devices, the synthesizer core feeds also a logic interface operating at 250 MHz with four 1.2-3.3 V external parallel channels. From reset time, the master-slave PLL combination achieves locking in a measured time of 450 ns, settling is resolved in ~4μs, and the output pulses across the antenna load are generated with a 3.42 ps RMS jitter standard deviation. The obtained phase noise of a continuous OOK stream at 1 and 4 GHz, 1 MHz offset, is -103 and -93 dBc/Hz, respectively.