Calibration of sampling-based multiplying delay-locked loop (MDLL)

An apparatus for calibrating a multiplying delay-locked loop (MDLL), the apparatus comprising:

• a locked-loop feedforward path comprising:
• a phase-frequency detector (PFD) configured to produce a phase indication signal based on a reference signal and a feedback signal;
• and
• means for sampling the phase indication signal to produce a sampled signal using a sampling component associated with at least one impedance;
• a voltage-controlled oscillator (VCO) coupled to the locked-loop feedforward path and configured to generate, responsive to the sampled signal, a VCO output signal at a VCO output node;
• a divider coupled to the VCO output node and configured to produce the feedback signal based on the VCO output signal;
• a multiplexer coupled to a VCO input node and configured to selectively forward the reference signal or the VCO output signal to the VCO input node;
• and
• calibration means for calibrating the means for sampling by adjusting the at least one impedance of the sampling component based on the reference signal and the VCO output signal.

A method for operating a multiplying delay-locked loop (MDLL), the method comprising:

• producing a control signal based on a reference signal and a feedback signal, including sampling a signal indicative of a phase difference between the reference signal and the feedback signal to obtain a sampled signal using at least one sampler component;
• running a voltage-controlled oscillator (VCO) to produce a VCO output signal responsive to the control signal;
• producing the feedback signal based on the VCO output signal;
• generating a sampler calibration signal based on the reference signal and the VCO output signal;
• and
• modifying the sampling based on the sampler calibration signal, including adjusting an impedance of the at least one sampler component using the sampler calibration signal.

An apparatus comprising:

• a multiplying delay-locked loop (MDLL) comprising:
• a voltage-controlled oscillator (VCO) configured to generate a VCO output signal based on the VCO output signal and a reference signal and responsive to a control signal, the VCO output signal having an output frequency that is a multiple of a reference frequency of the reference signal;
• a divider configured to produce a feedback signal based on the VCO output signal;
• a phase-frequency detector (PFD) configured to produce a phase indication signal based on the reference signal and the feedback signal;
• and
• a sampler comprising at least one component associated with at least one impedance and configured to produce a sampled signal based on the phase indication signal, the control signal based on the sampled signal;
• and
• a sampler calibrator configured to provide a sampler calibration signal to the sampler based on the reference signal and the VCO output signal to adjust the at least one impedance of the at least one component of the sampler.

An apparatus comprising:

• a multiplying delay-locked loop (MDLL) comprising:
• a locked-loop feedforward path comprising a sampler, a control output node, a feedback input node, and a reference input node coupled to a reference signal source;
• a voltage-controlled oscillator (VCO) comprising a VCO input node, a VCO output node, and a control input node coupled to the control output node;
• a multiplexer comprising a first input node, a second input node, and an output node, the first input node coupled to the reference signal source, the second input node coupled to the VCO output node, and the output node coupled to the VCO input node;
• and
• a divider comprising a divider input node and a divider output node, the divider input node coupled to the VCO output node, and the divider output node coupled to the feedback input node;
• and
• a sampler calibrator comprising a calibrator output node and a phase detector comprising a first calibrator input node, a second calibrator input node, and a phase-detector output node that is coupled to the calibrator output node;
• the first calibrator input node coupled to the reference signal source, the second calibrator input node coupled to the VCO output node, and the calibrator output node coupled to the sampler.