Methods and systems for digital dither
Methods and systems for applying digital dither includes methods and systems for applying digital dither in data converters, such as, for example, delta-sigma data converters. In an embodiment, an analog signal from a first path of a delta-sigma modulator is quantized to an m-bit digital signal and an n-bit dithered digital feedback signal is generated from at least a portion of the m-bit digital signal. The n-bit dithered digital feedback signal is converted to an analog feedback signal and fed back to a second path of the delta-sigma modulator. In an embodiment, the n-bit dithered digital feedback signal is generated by selecting one of a plurality of sets of n-bits from the m-bit digital signal depending upon a state of a dither control signal. The dither control signal can alternate between a plurality of states or pseudo-randomly switch between a plurality of states. In an embodiment, the m-bit digital signal is an m-bit thermometer code signal and the n-bit dithered digital feedback signal is generated by selecting between bits 0 through m-2 and bits 1 through m-1 of the m-bit digital signal. In an alternative embodiment, the m-bit digital signal is an m-bit thermometer code signal and the n-bit dithered digital feedback signal is generated by selecting between even and odd bits of the m-bit digital signal.
1. A method of applying digital dither, comprising the steps of:
(a) quantizing an analog signal to an m-bit digital signal;
(b) generating an n-bit dithered digital feedback signal from at least a portion of the m-bit digital signal;
(c) converting the n-bit dithered digital feedback signal to an analog feedback signal;
(d) feeding back the analog feedback signal to a second path of the delta-sigma modulator; and
(e) performing one or more feedback processes on at least one of the n-bit dithered digital feedback signal and the analog feedback signal.
2. The method of claim 1 , wherein the one or more feedback processes comprises mismatch shaping.
3. The method of claim 1 , wherein the one or more feedback processes comprises filtering.
4. The method of claim 1 , wherein the one or more feedback processes comprises integration.
5. The method of claim 1 , wherein the one or more feedback processes comprises selecting one or more feedback loops.
6. The method of claim 5 , wherein the one or more feedback processes further comprises selecting one or more inputs to the one or more feedback loops.
7. The method of claim 5 , wherein the one or more feedback processes further comprises selecting one or more outputs from said one or more feedback loops.
8. A delta-sigma modulator apparatus, comprising:
(a) means for quantizing an analog signal to an m-bit digital signal;
(b) means for generating an n-bit dithered digital feedback signal from at least a portion of the m-bit digital signal;
(c) means for converting the n-bit dithered digital feedback signal to an analog feedback signal;
(d) means for feeding back the analog feedback signal to a second path of the delta-sigma modulator; and
(e) means for performing one or more feedback processes on at least one of the n-bit dithered digital feedback signal and the analog feedback signal.
9. The apparatus of claim 8 , wherein the one or more feedback processes comprises mismatch shaping.
10. The apparatus of claim 8 , wherein the one or more feedback processes comprises filtering.
11. The apparatus of claim 8 , wherein the one or more feedback processes comprises integration.
12. The apparatus of claim 8 , wherein the one or more feedback processes comprises selecting one or more feedback loops.
13. The apparatus of claim 12 , wherein the one or more feedback processes further comprises selecting one or more inputs to the one or more feedback loops.
14. The apparatus of claim 12 , wherein the one or more feedback processes further comprises selecting one or more outputs from the one or more feedback loops.