This paper presents a novel divider-less scheme for automatic frequency calibration (AFC) of sub-sampling phase-locked loops. The proposed system works without any frequency dividers at all by utilizing the phase information provided by a serialized frequency detection through a sub-sampling phase detector. The detector is driven by evenly-spaced reference signals, which enables frequency detection and correction. The AFC is accompanied by a novel divider-less lock detector, which is also sample-based. The proposed system is configured to detect and correct all possible lock frequencies within the oscillator tuning range and is built apart from the analog front-end only with synthesizable standard cell CMOS logic.