Charge-domain pipelined analog-to-digital converter
An ADC implementation of a bucket brigade type charge transfer pipeline using Metal Oxide Semiconductor (MOS) Bucket Brigade Devices (BBDs) that can be used in Analog-to-Digital (A/D) converters and other applications. In one embodiment a control circuit provides independent control of charge storage and charge transfer timing. Other arrangements provide high-speed and high-accuracy (A/D) conversion by employing a “boosted” charge-transfer circuit. The implementation can also achieve lower power consumption and improved resolution compared to other charge-domain methods by the use of a tapered pipeline, in which the amount of charge being processed is reduced in later pipeline stages compared to earlier ones. Still other embodiments enable implementing more than one decision threshold per stage, to support multi-bit resolution per stage and RSD-type A/D conversion algorithms.
1. A charge domain pipeline using bucket brigade charge transfer comprising:
a first charge transfer circuit;
a second charge transfer circuit;
a node coupled to the first charge transfer circuit and the second charge transfer circuit;
a capacitor coupled to the node and to a clocked voltage;
a switched voltage coupled to the node; and
at least one of the first or second charge transfer circuits being a boosted charge transfer circuit.
2. The charge domain pipeline of claim 1 additionally comprising:
control circuitry configured to provide independent control of charge storage and charge transfer timing between the first charge transfer circuit and the second charge transfer circuit.
3. The charge domain pipeline of claim 2 wherein the control circuitry provides control of charge-transfer direction in the pipeline.
4. The charge domain pipeline of claim 1 comprising:
a second capacitor coupled to the node and to a conditional voltage, the second capacitor configured to provide conditional charge to the node.
5. The charge domain pipeline of claim 4 wherein the second capacitor provides conditional charge to the node based on a comparison of the voltage of the node with a reference voltage.
6. The charge domain pipeline of claim 4 further comprising a plurality of capacitors coupled to the node and to conditional voltages, each of the plurality of capacitors configured to provide conditional charge to the node.
7. The charge domain pipeline of claim 1 arranged to provide a differential charge domain pipeline and further comprising:
a third charge transfer circuit,
a fourth charge transfer circuit,
a second node coupled to the third charge transfer circuit and the fourth charge transfer circuit;
a second capacitor coupled to the node and to a second clocked voltage; and
a third and fourth capacitor coupled respectively to the first node and second node and configured to provide conditional charge to either the first charge transfer circuit or the third charge transfer circuit.
8. The differential charge domain pipeline of claim 7 wherein at least one of the third charge transfer circuit or the fourth charge transfer circuit is a boosted charge transfer circuit.
9. The differential charge domain pipeline of claim 7 wherein the third capacitor provides conditional charge based on a comparison of the voltages of the first node and the second node.
10. The differential charge domain pipeline of claim 7 further comprising a plurality of conditional charge capacitors coupled to the first and second node and configured to provide conditional charge to either the first charge transfer circuit or the third charge transfer circuit.
11. The differential charge domain pipeline of claim 10 wherein the plurality of capacitors provide conditional charge based on comparisons of the voltages of the first node and the second node at different thresholds.
12. A pipelined charge domain analog-to-digital converter using bucket brigade charge transfer comprising:
a first charge transfer circuit;
a second charge transfer circuit;
a node coupled to the first charge transfer circuit and the second charge transfer circuit;
a capacitor coupled to the node and to a clocked voltage;
a switched voltage coupled to the node; and
wherein at least one of the first or second charge transfer circuit is a boosted charge transfer circuit.
13. The pipelined charge domain analog-to-digital converter of claim 12 additionally comprising:
control circuitry configured to provide independent control of charge storage and charge transfer timing between the first charge transfer circuit and the second charge transfer circuit.
14. The charge domain pipeline of claim 12 arranged to provide a differential charge domain pipeline and further comprising:
a third charge transfer circuit;
a fourth charge transfer circuit;
a second node coupled to the third charge transfer circuit and the fourth charge transfer circuit;
a second capacitor coupled to the node and to a second clocked voltage; and
a third and fourth capacitor coupled to the first node and second node respectively and configured to provide conditional charge to either the first charge transfer circuit or the third charge transfer circuit.
15. A pipelined charge domain analog-to-digital converter using bucket brigade charge transfer comprising:
a first charge transfer circuit;
a second charge transfer circuit;
a node coupled to the first charge transfer circuit and the second charge transfer circuit;
a first clocked capacitor coupled to the node and to a clocked voltage;
a plurality of conditional charge capacitors coupled to the node and to conditional voltages, each of the plurality of conditional charge capacitors configured to provide conditional charge to the node.
16. The pipelined charge domain analog-to-digital converter of claim 15 additionally comprising:
a third charge transfer circuit,
a fourth charge transfer circuit,
a second node coupled to the third charge transfer circuit and the fourth charge transfer circuit;
a second clocked capacitor coupled to the node and to a clocked voltage;
a second plurality of conditional charge capacitors coupled to the first node and second node and configured to provide conditional charge to either the first charge transfer circuit or the third charge transfer circuit based on comparisons of the voltages of the first node and the second node at different thresholds.
17. The pipelined charge domain analog-to-digital converter of claim 15 wherein the pipeline is enabled to implement an RSD analog-to-digital conversion algorithm.
18. The pipelined charge domain analog-to-digital converter of claim 15 wherein the pipeline is enabled to implement binary stage scaling.
19. A pipelined charge domain analog-to-digital converter using bucket brigade charge transfer comprising:
a plurality of charge transfer circuits coupled in a cascading arrangement through a plurality of nodes, each node further coupled to a respective capacitor, with later nodes in the pipeline coupled to capacitors having a smaller capacitance than capacitors coupled to earlier nodes.
20. The charge domain pipeline of claim 19 arranged to provide a differential charge domain pipeline and further comprising:
a third charge transfer circuit;
a fourth charge transfer circuit;
a second node coupled to the third charge transfer circuit and the fourth charge transfer circuit;
a second capacitor coupled to the node and to a second clocked voltage; and
a third and fourth capacitor coupled to the first node and second node respectively and configured to provide conditional charge to either the first charge transfer circuit or the third charge transfer circuit.
21. A pipelined charge domain analog-to-digital converter using bucket brigade charge transfer comprising:
a plurality of charge transfer circuits coupled in a cascading arrangement through a plurality of nodes, each node further coupled to a respective capacitor, where the maximum output charge provided by each node is less that earlier nodes; and
control circuitry configured to provide independent control of charge storage and charge transfer timing between the plurality of charge transfer circuits.