An 820uW Low Jitter Digital Injection-Locked PLL Using Differential Multi-Phase Injection and Self-Calibration for Biosensing Applications

This paper presents a highly energy-efficient, low-jitter digital injection-locked phase-locked loop (ILPLL) tailored for the 2.4 GHz industrial scientific medical band. The proposed digital injection-locking architecture overcomes the limitations of conventional analog approaches regarding power, area, and robustness, and its incorporated differential multi-phase injection technique simultaneously suppresses jitter and further reduces power consumption. The misaligned injection pulse timing and non-optimized injection pulsewidth are digitally calibrated in background to maintain low power and low jitter across process, voltage, and temperature (PVT) variations. Fabricated in a 28-nm CMOS process, the proposed digital ILPLL achieves 542 fs RMS jitter with -65.8 dBc spur at 2.4 GHz working frequency. It consumes 820 ¼W power from a 0.6 V supply voltage, demonstrating the state-of-the-art energy efficiency along with a competitive jitter. In vitro experiment is conducted in a hospital for clinical trials, where the proposed digital ILPLL integrated into an SoC provides a local oscillator signal for the radio frequency front-end, enabling the system to wirelessly transmit electrocardiogram data in a battery-free manner.