Phase detector for reducing noise
The present invention provides a method and an apparatus for reducing noise. The apparatus includes a phase detector adapted to determine a phase difference between a first and a second signal, a first circuit adapted to generate a control signal based upon the determined phase difference, and a second circuit. The second circuit is adapted to receive a third signal, receive a fourth signal, modify the fourth signal based upon the control signal, and provide the third signal and the modified fourth signal to the phase detector as the first and second signals.
1. A delay locked loop, comprising:
an adjustable delay element adapted to receive an input clock signal and provide an output clock signal;
a control logic coupled to the adjustable delay element; and
a phase detector communicatively coupled to the control logic and adapted to determine a phase difference between the input clock signal and the output clock signal, the phase detector comprising:
a hysteresis adjuster adapted to provide a modified output clock signal based upon the output clock signal and a control signal;
a phase detector core adapted to determine a phase difference between the input clock signal and the modified output clock signal; and
a digital filter adapted to provide the control signal to the hysteresis adjuster based upon the phase difference.
2. The delay locked loop of claim 1 , wherein the hysteresis adjuster is further adapted to provide a modified input clock signal based upon the input clock signal.
3. The delay locked loop of claim 2 , wherein the phase detector core is adapted to determine a phase difference between the modified input clock signal and the modified output clock signal.
4. The delay locked loop of claim 1 , wherein the phase detector core is adapted to provide a signal indicative of the determined phase difference to the digital filter.
5. The delay locked loop of claim 4 , wherein the signal indicative of the determined phase difference is a binary signal.
6. The delay locked loop of claim 1 , wherein the digital filter is adapted to provide a signal indicative of a desired clock signal delay based upon the determined phase difference.
7. The delay locked loop of claim 6 , wherein the digital filter is adapted to provide the signal indicative of the desired clock signal delay to the control logic.
8. The delay locked loop of claim 6 , wherein the digital filter is a majority filter adapted to provide the signal indicative of the desired clock signal delay in response to at least two consecutive determined phase differences in the same direction.
9. The delay locked loop of claim 1 , wherein the hysteresis adjuster comprises a fixed delay and an adjustable delay, the fixed delay including at least one delay element and the adjustable delay including at least two delay elements, at least one of the delay elements in the adjustable delay being selectable based upon the control signal.
10. The delay locked loop of claim 1 , wherein the adjustable delay comprises a plurality of delay elements.
11. The delay locked loop of claim 1 , wherein the control logic comprises a shift register.
12. The delay locked loop of claim 1 , further comprising an intrinsic delay.