Interleaved delay line for phase locked and delay locked loops
An interleaved delay line for use in phase locked and delay locked loops is comprised of a first portion providing a variable amount of delay substantially independently of process, temperature and voltage (PVT) variations while a second portion, in series with the first portion, provides a variable amount of delay that substantially tracks changes in process, temperature, and voltage variations. By combining, or interleaving, the two types of delay, single and dual locked loops constructed using the present invention achieve a desired jitter performance under PVT variations, dynamically track the delay variations of one coarse tap without a large number of delay taps, and provide for quick and tight locking. Methods of operating delay lines and locked loops are also disclosed.
1. A memory device, comprising:
a plurality of memory cells; and
a plurality of peripheral devices for reading information from said plurality of memory cells, said peripheral devices comprising a locked loop comprising:
a delay line having a first portion having a plurality of taps for providing a variable amount of load adjustment and a second portion in series with said first portion, said second portion having a plurality of taps for providing a variable amount of drive adjustment;
a control circuit for controlling the amount of load adjustment and drive adjustment such that a tuning range of said delay line is equal to (M/2)(t dl +t dp ) where M is the number of taps, t dl is a range of delay provided by said first portion and t dp is a range of delay provided by said second portion;
a phase detector for producing signals for input to said control circuit; and
a feedback path for connecting an output of said delay line to an input of said delay line and to said phase detector.
2. The memory device of claim 1 wherein said first portion of said delay line has a small intrinsic delay and said second portion of said delay line has a higher intrinsic delay than said first portion.
3. The memory device of claim 1 wherein said range of delay of said first portion of said delay line is substantially independent of process, temperature and voltage variations and wherein said range of delay of said second portion of said delay line substantially tracks changes in process, temperature and voltage variations.
4. The memory device of claim 1 wherein said taps of said first portion of said delay line are for providing a stepwise varying of a value of a capacitor, and wherein said taps of said second portion of said delay line are for providing access to a plurality of signal paths.
5. The memory device of claim 4 wherein said signal paths include one of a series path through an inverter or a parallel path through inverters.
6. The memory device of claim 1 wherein the tuning range of said delay line is 240 ps to 420 ps.
7. A memory device, comprising:
a plurality of memory cells; and
a plurality of peripheral devices for reading information from said plurality of memory cells, said plurality of peripheral devices comprising a dual locked loop, comprising:
a first locked loop for establishing a phase relationship between an output signal and a reference signal;
a second locked loop responsive to said first locked loop and comprising:
a delay line having a first portion having a plurality of taps for providing a variable amount of load adjustment and a second portion in series with said first portion, said second portion having a plurality of taps for providing a variable amount of drive adjustment;
a control circuit for controlling the amount of load adjustment and drive adjustment such that a tuning range of said delay line is equal to (M/2)(t dl +t dp ) where M is a number of taps, t dl is a range of delay provided by said first portion and t dp is a range of delay provided by said second portion;
a phase detector for producing signals for input to said control circuit; and
a feedback path for connecting an output of said delay line to an input of said first locked loop and to said phase detector, said output signal being available at said output of said delay line.
8. The memory device of claim 7 wherein said first portion of said delay line has a small intrinsic delay and said second portion of said delay line has a higher intrinsic delay than said first portion.
9. The memory device of claim 7 wherein said range of delay of said first portion of said delay line is substantially independent of process, temperature and voltage variations and wherein said range of delay of said second portion of said delay line substantially tracks changes in process, temperature and voltage variations.
10. The memory device of claim 7 wherein said taps of said first portion of said delay line are for providing a stepwise varying of a value of a capacitor and wherein said taps of said second portion of said delay line are for providing access to a plurality of signal paths.
11. The memory device of claim 10 wherein said signal paths include one of a series path through an inverter or a parallel path through inverters.
12. The memory device of claim 7 wherein the tuning range of said delay line is 240 ps to 420 ps.
13. A system, comprising:
a processor;
a memory device; and
a bus for interconnecting said processor and said memory device, said memory device comprising a plurality of memory cells and a plurality of peripheral devices for reading information from said plurality of memory cells, said peripheral devices comprising a locked loop comprising:
a delay line having a first portion having a plurality of taps for providing a variable amount of load adjustment and a second portion in series with said first portion, said second portion having a plurality of taps for providing a variable amount of drive adjustment;
a control circuit for controlling the amount of load adjustment and drive adjustment such that a tuning range of said delay line is equal to (M/2)(t dl +t dp ) where M is a number of taps, t dl is a range of delay provided by said first portion and t dp is a range of delay provided by said second portion;
a phase detector for producing signals for input to said control circuit; and
a feedback path for connecting an output of said delay line to an input of said delay line and to said phase detector.
14. The system of claim 13 wherein said first portion of said delay line has a small intrinsic delay and said second portion of said delay line has a higher intrinsic delay than said first portion.
15. The system of claim 13 wherein said range of delay of said first portion of said delay line is substantially independent of process, temperature and voltage variations and wherein said range of delay of said second portion of said delay line substantially tracks changes in process, temperature and voltage variations.
16. The system of claim 13 wherein said taps of said first portion of said delay line are for providing a stepwise varying of a value of a capacitor, and wherein said taps of said second portion of said delay line are for providing access to a plurality of signal paths.
17. The system of claim 16 wherein said signal paths include one of a series path through an inverter or a parallel path through inverters.
18. The system of claim 13 wherein the tuning range of said delay line is 240 ps to 420 ps.
19. A system, comprising:
a processor;
a memory device; and
a bus for interconnecting said processor and said memory device, said memory device comprising a plurality of memory cells and a plurality of peripheral devices for reading information from said plurality of memory cells, said plurality of peripheral devices comprising a dual locked loop, comprising:
a first locked loop for establishing a phase relationship between an output signal and a reference signal;
a second locked loop responsive to said first locked loop and comprising:
a delay line having a first portion having a plurality of taps for providing a variable amount of load adjustment and a second portion in series with said first portion, said second portion having a plurality of taps for providing a variable amount of drive adjustment;
a control circuit for controlling the amount of load adjustment and drive adjustment such that a tuning range of said delay line is equal to (M/2)(t dl +t dp ) where M is a number of taps, t dl is a range of delay provided by said first portion and t dp is a range of delay provided by said second portion;
a phase detector for producing signals for input to said control circuit; and
a feedback path for connecting an output of said delay line to an input of said first locked loop and to said phase detector, said output signal being available at said output of said delay line.
20. The system of claim 19 wherein said first portion of said delay line has a small intrinsic delay and said second portion of said delay line has a higher intrinsic delay than said first portion.
21. The system of claim 19 wherein said range of delay of said first portion of said delay line is substantially independent of process, temperature and voltage variations and wherein said range of delay of said second portion of said delay line substantially tracks changes in process, temperature and voltage variations.
22. The system of claim 19 wherein said taps of said first portion of said delay line are for providing a stepwise varying of a value of a capacitor and wherein said taps of said second portion of said delay line are for providing access to a plurality of signal paths.
23. The system of claim 22 wherein said signal paths include one of a series path through an inverter or a parallel path through inverters.
24. The system of claim 19 wherein the tuning range of said delay line is 240 ps to 420 ps.