Methods and systems for digital dither
Methods and systems for applying digital dither in data converters, such as delta-sigma data converters. In one 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 another 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 or pseudo-randomly switch between a plurality of states. The m-bit digital signal may be an m-bit thermometer code signal.
1. An apparatus for applying digital dither, comprising:
an analog signal path;
a quantizer coupled to the analog signal path; and
a feedback path that receives an m-bit digital feedback signal from the quantizer, wherein the feedback path comprises:
a digital dither module that generates an n-bit dithered digital feedback signal from the m-bit digital feedback signal;
an n-bit digital-to-analog converter that converts the n-bit dithered digital feedback signal to an n-bit analog feedback signal; and
a feedback process module that performs one or more feedback processes on at least one of the n-bit dithered digital feedback signal and the n-bit analog feedback signal.
2. The apparatus of claim 1 , wherein the feedback process module comprises a mismatch shaper.
3. The apparatus of claim 1 , wherein the feedback process module comprises a filter.
4. The apparatus of claim 1 , wherein the feedback process module comprises an integrator.
5. The apparatus of claim 1 , wherein the feedback process module selects one or more feedback loops.
6. The apparatus of claim 5 , wherein the feedback process module selects one or more inputs to the one or more feedback loops.
7. The apparatus of claim 5 , wherein the feedback process module selects one or more outputs from the one or more feedback loops.