Binary-weighted delta-sigma fractional-N frequency synthesizer with digital-to-analog differentiators canceling quantization noise

摘要

A phase lock loop includes a quantization circuit that generators an out of phase noise cancellation signal from an error in a delta-sigma modulator and applies the noise cancellation signal to the charge pump. The quantization circuit includes a digital-to-analog differentiator. The digital-to-analog differentiator may be, for example, a single-bit first-order digital-to-analog differentiator, a single-bit second-order digital-to-analog differentiator, or a full M-bit binary-weighted digital to analog differentiator.