  This work presents a new frequency acquisition method using semi-rotational
frequency detection (SRFD) algorithm for a reference-less clock and data
recovery (CDR) in a serial-link receiver. The proposed SRFD algorithm
classifies the bang-bang phase detector(BBPD) outputs to estimate the current
phase state, and detects the frequency mismatch between the input data and the
sampling clock. The VCO-track path in a digital loop filter (DLF) enables
online calibration of a drifted frequency of VCO caused by temperature or
voltage variation after a frequency acquisition. The proposed algorithm can be
implemented as a digitally-synthesized circuit, lowering design efforts for
referenceless CDRs. A 10 Gbps transceiver IC with the proposed algorithm,
fabricated in a 65nm CMOS process, demonstrates successful recovery of the
input phase without any reference clock.
