Method for calbrating a pipelined continuous-time sigma delta modulator
AssigneeTexas Instruments Incorporated
InventorsPatrick Satarzadeh, Venkatesh Srinivasan, Charles Sestok
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Abstract
Traditionally, pipelined continuous-time (CT) sigma-delta modulators (SDM) have been difficult to build due at least in part to the difficulties in calibrating the pipeline. Here, however, a pipelined CT SDM is provided that has an architecture that is conducing to being calibrated. Namely, the system includes a digital filter and other features that can be adjusted to account for input imbalance errors and well as quantization leakage noise.
Claims7
An apparatus for calibrating at least a portion of a pipelined continuous-time (CT) sigma-delta modulator (SDM), wherein the CT SDM includes a first stage, a second stage, and a first digital-to-analog converter (DAC) coupled between the first and second stages, and a digital filter that is coupled to the first and second stages, and wherein the second stage includes a second DAC, the apparatus comprising:
- means for determining a ratio of a gain of the first DAC to a gain of the second DAC;
- means for adjusting a gain of a digital filter to be approximately equal to the ratio of the gain of the first DAC to the gain of the second DAC;
- and
- means for adjusting the digital filter to maximize a cross-correlation between an output of the digital filter and the output of the second stage.
An apparatus for calibrating at least a portion of a pipelined CT SDM, the apparatus comprising:
- means for disabling a first DAC, wherein the first DAC is located between a first stage and a second stage of the pipelined CT SDM;
- means for applying a predetermined input signal to the second stage while the first DAC is disabled;
- means for enabling the first DAC;
- means for disabling a second DAC within the second stage;
- means for applying the predetermined input signal to the second stage while the using the first DAC as a feedback DAC for the second stage;
- means for determining gains of the first and second DACs;
- means for adjusting a gain of a digital filter to be a function of the gains of the first and second DACs, and
- wherein the digital filter is coupled to the first and second stages.
Dependencies are inferred from the claim text.