Digital phase lock loop
Techniques of designing a digital phase lock loop are disclosed. In one embodiment, the digital phase lock loop comprises a synchronization unit producing a producing a plurality of clock signals in accordance with a seed clock signal having a frequency, each of the clock signals having a modified frequency over the frequency of the seed clock signal and a phase shift from each other; a phase-frequency detection unit receiving an input signal and a feedback signal, and sampling the input signal and the feedback signal in accordance with the clock signals to determine differences in phase and frequency between the input signal and the feedback signal; a digital control oscillator receiving the clock signals and producing an output signal in reference to the differences from phase-frequency detection unit, and subsequently, a digitally controlled clock signal is produced.
1. A digital phase lock loop comprising:
a synchronization unit producing a plurality of clock signals in accordance with a seed clock signal having a frequency, each of the clock signals having (i) a modified frequency over the frequency of the seed clock signal and (ii) a phase shift from each other;
a digital control oscillator receiving the clock signals and producing an output signal in reference to a received signal;
a phase-frequency detection unit in which a phase and frequency of an input signal is detected and compared with the output signal from the digital control oscillator, wherein the received signal pertains to any errors between the input signal and the output signal;
a filter (i) coupled to the digital control oscillator and (ii) configured to filter out possible noises in the output signal, wherein the output signal comprises a digitally controlled clock signal; and
a first divider coupled between the digital oscillator and the filter, wherein the output signal is scaled down in the first divider and further filtered in the filter to produce a digitally controlled clock signal.
2. The digital phase lock loop of claim 1 , wherein the output signal is modified by a second divider before being fed to the phase-frequency detection unit.
3. The digital phase lock loop of claim 2 , wherein the first divider and the second divider are programmable.
4. The digital phase lock loop of claim 3 , wherein a dividing factor of the first divider or the second divider is determined in accordance with a display resolution.
5. The digital phase lock loop of claim 4 , wherein the digital phase lock loop is used to control a display having the display resolution.
6. The digital phase lock loop of claim 1 , wherein the filter is configured to filter out phase quantization noise on the output signal and provide the original frequency of the input signal.
7. The digital phase lock loop of claim 1 , wherein the input signal is implemented as a video horizontal synchronization signal having a low frequency.
8. A digital phase lock loop comprising:
a synchronization unit producing a plurality of clock signals in accordance with a seed clock signal having a frequency, each of the clock signals having a modified frequency over the frequency of the seed clock signal and a phase shift from each other;
a phase-frequency detection unit (i) receiving an input signal and a feedback signal and (ii) sampling the input signal and the feedback signal in accordance with the clock signals to determine differences in phase and frequency between the input signal and the feedback signal; and
a digital control oscillator receiving the clock signals and producing an output signal in reference to the differences from phase-frequency detection unit, wherein a signal representing the differences is divided in a divider to be the feedback signal.
9. The digital phase lock loop of claim 8 , wherein the signal representing the differences at the same time is fed to another divider coupled to a filter.
10. The digital phase lock loop of claim 9 , wherein the filter is configured to filter out possible noise from the signal representing the differences.
11. The digital phase lock loop of claim 9 , wherein the filter subsequently produces a digitally controlled clock signal.
12. The digital phase lock loop of claim 8 , wherein there are N clocks, and the frequency of each of the clocks is the frequency of the seed clock signal divided by N.
13. The digital phase lock loop of claim 8 , wherein the input signal is implemented as a video horizontal synchronization signal having a low frequency.
14. A digital phase lock loop comprises:
a synchronization unit producing a plurality of clock signals in accordance with a seed clock signal having a frequency, each of the clock signals having a modified frequency over the frequency of the seed clock signal and a phase shift from each other;
a digital control oscillator receiving the clock signals and producing an output signal in reference to a received signal; and
a phase-frequency detection unit in which a phase and frequency of an input signal is detected and compared with the output signal from the digital control oscillator, wherein (i) the received signal pertains to any errors between the input signal and the output signal, (ii) the output signal is modified by (a) a first divider before being fed to the phase-frequency detection unit and (b) a second divider to scale down the output signal, (iii) the first divider and the second divider are programmable, (iv) a dividing factor of the first divider and the second divider is determined in accordance with a display resolution, and (v) the digital phase lock loop is used to control a display having the display resolution.
15. The digital phase lock loop of claim 14 , wherein the phase-frequency detection unit is configured to sample a feedback signal generated by the first divider and the input signal to determine differences in phase and frequency between the input signal and the feedback signal.
16. The digital phase lock loop of claim 14 , wherein a filter is configured to subsequently produce a digitally controlled clock signal in response to said scaled down output signal.
17. The digital phase lock loop of claim 14 , wherein the input signal is implemented as a video horizontal synchronization signal having a low frequency.
18. The digital phase lock loop of claim 16 , wherein the filter is configured to filter out phase quantization noise on the output signal and provide the original frequency of the input signal.
19. The digital phase lock loop of claim 14 , wherein the second divider is coupled between the digital control oscillator and a filter.