Clock data recovery

A circuit, comprising:

• a voltage-controlled oscillator (VCO) including a VCO output;
• a frequency divider including a frequency divider input, a first frequency divider output, and a second frequency divider output, the frequency divider input coupled to the VCO output;
• and
• a phase-frequency detector (PFD) including a data input, a first PFD input, a second PFD input, and a control output, the control output coupled to the VCO, the first PFD input coupled to the first frequency divider output, and the second PFD input coupled to the second frequency divider output, the first frequency divider output is configured to provide a first frequency divider signal and the second frequency divider output is configured to provide a second frequency divider signal 90 degrees out of phase with respect to the first frequency divider signal, and the PFD is configured to detect occurrence of an edge of a signal on the data input while the second frequency divider signal is logic high followed by an absence of any edges of the signal on the data input while the second frequency divider signal is low immediately following the second frequency divider signal being logic high;
• wherein the PFD includes:
• a first flip-flop having a non-inverted first clock input coupled to the data input;
• a second flip-fop having an inverted second clock input coupled to the data input;
• a third flip-flop having a non-inverted third clock input coupled to the data input;
• a fourth flip-flop having an inverted fourth clock input coupled to the data input;
• a first logic gate having first and second logic gate inputs and a first logic gate output, the first logic gate input coupled to an output of the first flip-flop and the second logic gate input coupled to an output of the second flip-flop;
• a second logic gate having third and fourth logic gate inputs and a second logic gate output, the third logic gate input coupled to an output of the third flip-flop and the fourth logic gate input coupled to an output of the second flip-flop;
• a first latch having a first latch input and a first latch output, the first latch input coupled to the first logic gate output;
• a third logic gate having fifth and sixth logic gate inputs and a third logic gate output, the fifth logic gate input coupled to the first latch output and the sixth logic gate input coupled to the second logic gate output;
• and
• a second latch having a second latch input and a second latch output, the second latch input coupled to the third logic gate output.

A circuit, comprising:

• a voltage-controlled oscillator (VCO) including a VCO output;
• a frequency divider including a frequency divider input, a first frequency divider output, and a second frequency divider output, the frequency divider input coupled to the VCO output;
• and
• a phase-frequency detector (PFD) including a data input, a first PFD input, a second PFD input, and a control output, the control output coupled to the VCO, the first PFD input coupled to the first frequency divider output, and the second PFD input coupled to the second frequency divider output, the first frequency divider output is configured to provide a first frequency divider signal and the second frequency divider output is configured to provide a second frequency divider signal 90 degrees out of phase with respect to the first frequency divider signal, and the PFD is configured to detect occurrence of an edge of a signal on the data input while the second frequency divider signal is logic high followed by an absence of any edges of the signal on the data input while the second frequency divider signal is low immediately following the second frequency divider signal being logic high;
• wherein the PFD includes:
• a first flip-flop having a non-inverted first clock input coupled to the data input;
• a second flip-fop having an inverted second clock input coupled to the data input;
• a third flip-flop having a non-inverted third clock input coupled to the data input;
• a fourth flip-flop having an inverted fourth clock input coupled to the data input;
• a first logic gate having first and second logic gate inputs and a first logic gate output, the first logic gate input coupled to an output of the first flip-flop and the second logic gate input coupled to an output of the second flip-flop;
• a second logic gate having third and fourth logic gate inputs and a second logic gate output, the third logic gate input coupled to an output of the third flip-flop and the fourth logic gate input coupled to an output of the second flip-flop;
• and
• a pulse generator coupled to the first, second, third, and fourth flip-flops.