Digital to analog converter with thermometer coding and methods for use therewith
View Patent ↗A digital to analog converter (DAC) includes a thermometer coder that processes a digital input based on a thermometer coding, and generates a plurality of micro-current source inputs and a plurality of micro-current source analog controls. A plurality of micro-current sources generate a corresponding plurality of micro-current source outputs in response to the plurality of micro-current source inputs, wherein first selected ones of the plurality of micro-current sources are powered-off in response to the plurality of micro-current source analog controls. A summing circuit generates an analog output based on a sum of the corresponding plurality of micro-current source outputs.
1. A digital to analog converter (DAC) comprising:
a thermometer coder configured to process a digital input based on a thermometer coding to generate a plurality of micro-current source inputs and a plurality of micro-current source analog controls;
a plurality of micro-current sources, coupled to the thermometer coder, configured to generate a corresponding plurality of micro-current source outputs in response to the plurality of micro-current source inputs, wherein first selected ones of the plurality of micro-current sources are powered-off in response to the plurality of micro-current source analog controls; and
a summing circuit, coupled to the plurality of micro-current sources, configured to generate an analog output based a sum of the corresponding plurality of micro-current source outputs.
2. The DAC of claim 1 wherein the plurality of micro-current source inputs are ternary-coded.
3. The DAC of claim 1 wherein the plurality of micro-current source outputs have one of: a positive current state, a negative current state and a neutral current state.
4. The DAC of claim 1 wherein the thermometer coder is configured to process a first value of the digital input based on the thermometer coding to generate the plurality of micro-current source inputs to ramp from a prior value of the analog output to a new value corresponding the first value of the digital input.
5. The DAC of claim 1 wherein the thermometer coder is configured to process a first value of the digital input based on the thermometer coding to generate the plurality of micro-current source inputs to generate currents from second selected ones of the plurality of micro-current sources.
6. The DAC of claim 5 wherein the second selected ones of the plurality of micro-current sources are included in the first selected ones of the plurality of micro-current sources.
7. The DAC of claim 5 wherein the second selected ones of the plurality of micro-current sources are a proper subset of the first selected ones of the plurality of micro-current sources.
8. The DAC of claim 5 wherein the first selected ones of the plurality of micro-current sources include x+C of the plurality of micro-current sources, where the second selected ones of the plurality of micro-current sources include x of the plurality micro-current sources and wherein C is a predetermined value.
9. A digital to analog converter (DAC) comprising:
a thermometer coder configured to process a digital input based on a thermometer coding to generate a plurality of micro-current source inputs;
a plurality of ternary micro-current sources, coupled to the thermometer coder, configured to generate a corresponding plurality of micro-current source outputs in response to the plurality of micro-current source inputs, wherein first selected ones of the plurality of ternary micro-current sources are powered-off; and
a summing circuit, coupled to the plurality of ternary micro-current sources, configured to generate an analog output based a sum of the corresponding plurality of micro-current source outputs.
10. The DAC of claim 9 wherein the plurality of micro-current source outputs have one of: a positive current state, a negative current state and a neutral current state.
11. The DAC of claim 9 wherein the thermometer coder is configured to process a first value of the digital input based on the thermometer coding to generate the plurality of micro-current source inputs to ramp from a prior value of the analog output to a new value corresponding to the first value of the digital input.
12. The DAC of claim 9 wherein the thermometer coder is configured to process a first value of the digital input based on the thermometer coding to generate the plurality of micro-current source inputs to generate currents from second selected ones of the plurality of ternary micro-current sources; and
wherein the first selected ones of the plurality of micro-current sources include x+C of the plurality of micro-current sources, where the second selected ones of the plurality of micro-current sources include x of the plurality micro-current sources and wherein C is a predetermined value.
13. The DAC of claim 9 wherein the digital input corresponds to a value of an orthogonal frequency division multiplexed symbol for upstream transmission from a cable modem to a cable modem termination system.
14. A method comprising:
processing a digital input based on a thermometer coding to generate a plurality of micro-current source inputs and a plurality of micro-current source analog controls;
generating, via a plurality of micro-current sources, a corresponding plurality of micro-current source outputs in response to the plurality of micro-current source inputs, wherein first selected ones of the plurality of micro-current sources are powered-off in response to the plurality of micro-current source analog controls; and
generating an analog output by summing the corresponding plurality of micro-current source outputs.
15. The method of claim 14 wherein the plurality of micro-current source inputs are ternary-coded.
16. The method of claim 14 wherein the plurality of micro-current source outputs have one of: a positive current state, a negative current state and a neutral current state.
17. The method of claim 14 wherein the plurality of micro-current source inputs are generated to ramp the analog output from a prior value to a new value.
18. The method of claim 14 wherein the plurality of micro-current source inputs are generated to generate currents from second selected ones of the plurality of micro-current sources.
19. The method of claim 18 wherein the second selected ones of the plurality of micro-current sources are a proper subset of the first selected ones of the plurality of micro-current sources.
20. The method of claim 18 wherein the first selected ones of the plurality of micro-current sources include x+C of the plurality of micro-current sources, where the second selected ones of the plurality of micro-current sources include x of the plurality micro-current sources and wherein C is a predetermined value.