Texas Instruments Incorporated
High Gain Detector Techniques for High Bandwidth Low Noise Phase-Locked Loops

Abstract:

In described examples, a phase locked loop (PLL) has a first phase detector cell (PD) that has a gain polarity. The first PD cell has a phase error output and inputs coupled to a reference frequency signal and a feedback signal. A second PD cell has an opposite gain polarity. The second PD cell has a phase error output and inputs coupled to the reference frequency signal and the feedback signal. A loop filter has a feedforward path and a (lossy) integrating path coupled to an output of the filter. The feedforward path has a third PD cell that has phase error output AC-coupled to the filter output. The integrating path includes an opamp that has an inverting input coupled to the first PD cell phase error output and a non-inverting input coupled to the second PD cell phase error output.