US 7,253,669 B1 · High resolution digital loop circuit

Abstract

A digital feedback loop circuit achieves a resolution as good as the intrinsic resolution of the delay element of the circuit, notwithstanding the presence of a feedback counter/divider of integer value N that might otherwise be expected to multiply the minimum resolution by N. Output altering circuitry is used to alter the error feedback signal for M out of every N feedback cycles in such a way that the overall delay over N cycles can be controlled to within the resolution of the delay element. In one embodiment, the output altering circuitry includes a second counter whose maximum value is controllable and that outputs a signal whose value changes after its current maximum value has been reached. In another embodiment, the output altering circuitry includes a lookup table preloaded with sequences of output signals, with the sequence selected by a controller.

Claims36

Dependent claims

A digital feedback loop circuit comprising:

a controllable output signal generator to generate a loop circuit output signal;
a feedback counter to divide said loop circuit output signal by an integer N;
a detector to compare said divided loop circuit output signal to an input reference signal and generate a comparison signal;
a controller responsive to said comparison signal to generate an output control signal to adjust said controllable output signal generator to lock said loop circuit output signal to said input reference signal;
and
circuitry to selectably alter said output control signal to adjust resolution of said loop circuit output signal;
said circuitry comprising:
a control signal modifier responsive to said output control signal to produce a modified control signal;
a selector to select one of said output control signal and said modified control signal as an input to said controllable output signal generator for M loop cycles (M<N) and to select said output control signal for N−M loop cycles.

6 more elements

A digital feedback loop circuit comprising:

means for controllably generating a loop circuit output signal;
means for dividing said loop circuit output signal by an integer N;
means for comparing said divided loop circuit output signal to an input reference signal and generating a comparison signal;
means responsive to said comparison signal for generating an output control signal to adjust said means for controllably generating a loop circuit output signal for locking said loop circuit output signal to said input reference signal;
and
means for selectably altering said output control signal to adjust resolution of said loop circuit output signal;
said means for selectably altering comprising:
means responsive to said output control signal for producing a modified control signal;
means for selecting one of said output control signal and said modified control signal as an input to said means for controllably generating said loop circuit output signal for M loop cycles (M<N) and for selecting said output control signal for N−M loop cycles.

6 more elements

A method for operating a digital feedback loop circuit, said method comprising:

controllably generating a loop circuit output signal;
dividing said loop circuit output signal by an integer N and feeding back said divided loop circuit output signal;
comparing said divided loop circuit output signal to an input reference signal and generating a comparison signal;
responsive to said comparison signal, generating an output control signal for locking said loop circuit output signal to said input reference signal;
and
selectably altering said output control signal to adjust resolution of said loop circuit output signal;
said selectably altering comprising:
responsive to said output control signal, producing a modified control signal;
selecting one of said output control signal and said modified control signal as an input for controllably generating said loop circuit output signal for M loop cycles (M<N) and for selecting said output control signal for N−M loop cycles.

6 more elements

Dependencies are inferred from the claim text.

High resolution digital loop circuit

Life of this patent

High resolution digital loop circuit

Life of this patent

Abstract

Claims36