Fully differential charge pump with switched-capacitor common-mode feedback

摘要

Certain aspects of the present disclosure provide methods and apparatus for implementing a fully differential charge pump circuit that eliminates a source of noise and power consumption by using a low-noise switched-capacitor common-mode feedback (CMFB) circuit, rather than a continuous-time amplifier-based CMFB circuit. The fully differential charge pump circuit presented in this disclosure includes the switched-capacitor CMFB (SC-CMFB) unit connected to differential output nodes of the charge pump and provides a feedback signal to the charge pump to control a common-mode voltage of the differential signals based on a reference common-mode voltage. In certain aspects, a replica phase-frequency detector (PFD), a frequency divider, and a non-overlapping clock generator provides control signals for the SC-CMFB circuit.

主权项

1. A differential charge pump circuit, comprising:
a charging circuit comprising a plurality of charge pump branches and configured to generate differential signals at differential output nodes; and a switched-capacitor common-mode feedback (SC-CMFB) circuit coupled to the differential output nodes of the charging circuit, wherein the SC-CMFB circuit is configured to:
receive a reference common-mode voltage (Vcm); andgenerate a common-mode feedback signal configured to bias the charge pump branches such that an actual Vcm of the differential signals equals the reference Vcm, wherein at least one control input to the SC-CMFB circuit is based on a signal generated by a first phase-frequency detector (PFD).