Patent ID: 6111470
Filing Date: 2000-08-29
Classification: H03L

Abstract:
A phase-locked loop circuit comprising:a reference source that generates a reference signal;a voltage controlled oscillator (VCO) that generates a VCO signal; anda phase comparator coupled to the reference source and the VCO, for detecting a phase error between the reference signal and the VCO signal, the phase comparator having an up-command output and a down-command output in response to the phase error;a charge pump, for generating current to adjust phase alignment, the charge pump having a first input couplable to the up-command output when the second input is coupled to the down-command output and having the first input couplable to the down-command output when the second input is coupled to the up-command output;a chopper stabilizer circuit for modulating noise by simultaneously decoupling the first input from the up-command output and the second input from the down-command output and coupling the first input to the down-command output and the second input to the up-command output, whereby the chopper stabilizer circuit has a first output for outputting one of an up-command signal and a down-command signal and a second output for outputting one of an up-command signal and down command signal; anda filter, coupled to an output of the charge pump, for filtering the modulated noise.