Low power high speed A/D converter

1. An analog-to-digital converter (ADC) comprising:

a coarse-measurement circuit comprising a plurality of comparators configured for generating a coarse digital measurement of an analog input signal;

a fine-measurement circuit comprising a plurality of subsets of dynamic comparators, wherein each dynamic comparator is configurable for being activated by a clock signal, and each subset is configured for performing a fine digital measurement of the analog input signal;

an activation circuit configured for processing the coarse measurement and an input clock signal for generating a set of activation signals for activating one of the plurality of subsets to generate the fine digital measurement; and

a thermometer-to-bubble code encoder configured for converting a thermometer code output from the coarse-measurement circuit to a bubble code for input to the activation circuit.

2. The ADC recited in claim 1 , further comprising a sample-and-hold circuit configured for providing the analog input signal.

3. The ADC recited in claim 1 , further comprising an encoder configured for generating a binary coded digital output from the coarse digital measurement and the fine digital measurement.

4. The ADC recited in claim 1 , wherein each of the coarse-measurement circuit and the fine-measurement circuit comprises a reference circuit.

5. The ADC recited in claim 1 , wherein the activation circuit comprises a strobe configured for generating the input clock signal.

6. The ADC recited in claim 1 , wherein the activation circuit comprises a plurality of logic circuits, each of the logic circuits configured for processing the input clock signal and a bubble code input for producing a plurality of activation signal outputs.

7. The ADC recited in claim 6 , wherein each of the logic circuits comprises an array of AND logic gates.

8. The ADC recited in claim 1 , wherein coarse measurement circuit has coarse-measurement resolution, and each of the plurality of subsets is configured for performing the fine measurement over a voltage range that is greater than or equal to the coarse measurement resolution.

9. The ADC recited in claim 1 , wherein the fine measurement circuit is configured for performing the fine measurement across overlapping voltage ranges.

10. The ADC recited in claim 1 , wherein at least one of the dynamic comparators is included in a plurality of the subsets.

11. A method of analog-to-digital conversion, comprising:

providing a coarse measurement of an analog input signal;

converting the coarse measurement from a thermometer code to a bubble code;

generating a set of activation signals from the bubble code and an input clock signal, the activation signals comprising a set of clock signals and at least one set of constant-value signals; and

activating a subset of a plurality of dynamic comparators for performing a fine measurement of the analog input signal.

12. The method recited in claim 11 , wherein each of the plurality of dynamic comparators is configured for being activated by a clock signal.

13. The method recited in claim 11 , wherein providing the coarse measurement is characterized by a coarse-measurement resolution, and performing the fine measurement employs a voltage range equal to or greater than the coarse-measurement resolution.

14. The method recited in claim 11 , wherein the fine measurement employs overlapping voltage ranges.

15. The method recited in claim 11 , further comprising generating a binary coded digital output from the coarse digital measurement and the fine digital measurement.

16. The method recited in claim 11 , wherein each of the constant-value signals prevents its associated dynamic comparator from being activated into its precharge state.

17. An analog-to-digital conversion system, comprising:

means for providing a coarse measurement of an analog input signal;

means for converting the coarse measurement from a thermometer code to a bubble code;

means for generating a set of activation signals from the bubble code and an input clock signal, the activation signals comprising a set of clock signals and at least one set of constant-value signals; and

means for activating a subset of a plurality of dynamic comparators for performing a fine measurement of the analog input signal.

18. A method of analog-to-digital conversion, comprising:

providing a coarse measurement of an analog input signal;

converting the coarse measurement from a thermometer code to a bubble code;

generating a set of activation signals from the bubble code and an input clock signal, the activation signals comprising a set of clock signals and at least one set of constant-value signals, wherein each of the constant-value signals prevents its associated one of a plurality of dynamic comparators from being activated into its precharge state; and

activating a subset of the plurality of dynamic comparators for performing a fine measurement of the analog input signal.