charge pump nonlinearity sigma delta noise
Im very interested with what you said. That's exactly what I want to know. But it's hard to understand the non-linearity of charge pump will fold the out-band quantization noise to in-band. Could you please give a more detailed explanition or give some reference? Thanks a lot!
By the way, as you said a constant bias current at charge pump output can reduce the non-linearity of charge pump mismatch. But it's known that in the integer-N situation this constant bias current will cause large reference spur! Will this also cause reference spur for fractional-N frequency synthesizer?