Combining fully-differential and single-ended signal processing in a delta-sigma modulator
AssigneeCrystal Semiconductor Corporation
InventorsEric J. Swanson, Bruce P. Del Signore
Life of this patent
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Abstract
An oversampling analog-to-digital modulator includes an analog loop filter which has a first integrator stage which is a single-ended integrator. The second, third, and fourth integrator stages are fully-differential integrators. The first integrator provides the required thermal noise characteristics of the loop filter with only one feedback capacitor which is external to the integrated circuit chip, while the fully-differential integrator stages provide improved suppression of charge injection transients.
Claims9
A plurality of serially coupled integrators in an analog-to-digital modulator characterized in that at least one of said integrators is a single-ended integrator and at least another of said integrators is a fully-differential integrator.
An analog-to-digital modulator including a summing circuit coupled to an analog loop filter, the output of which is coupled to a quantizer, the output of which is coupled to a D/A converter, the output of which is coupled to one input of said summing circuit, a second input of said summing circuit being adapted to receive an analog input signal, wherein the analog loop filter comprises a plurality of serially coupled integrators, at least one of said integrators is a single-ended integrator and at least another of said integrators is a fully-differential integrator.
An analog loop filter comprising a plurality of serially coupled integrator stages in which at least one of said integrator stages includes a single-ended integrator and at least another of said integrator stages includes a fully-differential integrator.
An analog-to-digital modulator comprising:
- a) an input terminal for receiving an analog input voltage;
- b) an input resistor coupled to said input terminal and to a summing node;
- c) a current resistor coupled between said summing node and a voltage reference to form a current source path to said summing node;
- d) a single-ended integrator having its input coupled to said summing node;
- e) a plurality of fully-differential integrator stages connected in series, said plurality having an input coupled to the output of said single-ended integrator and including at least one feedback group within said plurality of discrete time integrators;
- e) a plurality of feedforward elements each coupled to different nodes within said plurality of discrete time integrator stages;
- and
- f) a one bit analog-to-digital converter for receiving the outputs of said plurality of feedforward elements and for providing a digital output of the analog-to-digital modulator, said analog-to-digital converter output also being used to switch a current sink path coupled to said summing node, said current switch being responsive to the digital state of the output of said analog-to-digital modulator.
Dependencies are inferred from the claim text.