A 0.144 mm²12.5-16GHz PVT-Tolerant Dual-Path Offset-Charge-Pump-Based Fractional-N PLL Achieving 72.9 fSRMs Jitter, -271.5dB FoMN, and Sub-10% Jitter Variation

The <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">sub-100fsRMS</tex> jitter fractional-N (FN) phase-locked loop (PLL) is essential for high-speed wireless/wireline transceivers and data converters. Several reported low-jitter FN-PLLs are listed in Fig. 1. Both the sampling phase detector (SPD) [1] and the bang-bang PD (BBPD) [2] based PLLs assisted by the digital-to-time converter (DTC) leverage high phase-detection gain (K <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">PD</inf> ) to suppress the in-band phase noise (PN). Regrettably, the low-jitter DTC with sufficient tuning range and linearity is required to avoid jitter degradation at the cost of power and figure-of-merit (FoM) improvement. To prevent the DTC-induced issue, the voltage-domain digital-to-analog (VDAC) based sub-sampling PLL (SS-PLL) replaces a DTC with a VDAC, whose noise can be suppressed by high K <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">PD</inf> [3]. Yet, the usage of the digitally-controlled delay line (DCDL) to keep high K <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">PD</inf> adds extra noise. Particularly, the noises of the DTC and DCDL vary much with process, voltage, and temperature (PVT) variation, thus sensitizing the PLL jitter over PVT variation; and both DTC and VDAC necessitate complicated calibration to cope with their gain mismatch or nonlinearity, thus occupying large area. Alternatively, widely used charge-pump-based PLL (CP-PLL) [5], [6] is robust and free of DTC or VDAC, and the CP nonlinearity is addressed by the offset CP (OCP) [5], whereas the long turn-on time <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">(tₒₙ)</tex> of the OCP and low K <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">PD</inf> elevate the in-band PN, and the integral capacitor is bulky.