Sigma-Delta Quantizer Reference Trimming for Higher SNDR
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Solution Overview
Problem
Sigma-delta modulators face challenges in achieving high signal-to-noise and distortion ratio with minimal components, as higher detection levels in quantizers increase complexity and require more components, while manufacturing variations in CMOS devices lead to inconsistent performance.
Innovation Solution
Trimming the reference voltages used by quantizers in sigma-delta modulators to optimize the signal-to-noise plus distortion ratio, rather than relying on default voltages, by testing and selecting the optimal voltage levels through a programmable reference voltage circuit and SNDR module.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If quantizers with higher detection levels are used to improve signal-to-noise ratio, then performance is improved, but device complexity increases and more components are required
Solution Approach 1:
The patent applies parameter changes by trimming the reference voltage levels of the quantizer to optimal values. Instead of increasing the number of detection levels to improve signal-to-noise ratio, the invention optimizes the existing quantizer parameters (reference voltages) to achieve better performance with the same number of components. This resolves the contradiction by improving measurement precision through parameter optimization rather than increasing system complexity.
2Device complexity
If default reference voltages are used in quantizers, then device simplicity is maintained, but performance is suboptimal due to manufacturing variations
Solution Approach 1:
The patent applies preliminary action by performing reference voltage trimming during the manufacturing or initialization phase. The optimal reference voltage levels are determined in advance through testing and trimming, and then stored for use during normal operation. This preliminary optimization ensures consistent high performance across manufacturing variations without adding complexity to the operational device structure.
3Measurement precision
If reference voltages are trimmed to optimize performance, then signal-to-noise ratio is improved, but additional components and complexity are introduced
Solution Approach 1:
The patent minimizes the additional complexity by implementing a compact reference voltage trimming circuit that adjusts only the reference voltage parameters. The trimming mechanism uses minimal additional components (such as voltage taps and selection logic) to optimize the reference voltage levels. This approach achieves improved signal-to-noise plus distortion ratio while keeping the increase in device complexity to a minimum.
4Reliability
If manufacturing variations are accommodated by design margins, then consistency is improved, but performance is reduced
Solution Approach 1:
The patent applies preliminary action by performing reference voltage trimming during manufacturing to compensate for process variations. Each device is individually trimmed to achieve optimal reference voltage levels despite manufacturing variations. This preliminary customization ensures that each device achieves its maximum potential performance without requiring conservative design margins, thereby improving both reliability and measurement precision.
Data Source
AI summary
A sigma delta modulator includes a first circuit that receives an analog signal and provides an intermediate signal and a first quantizer signal and further includes a first quantizer that receives the first quantizer signal and provides a first quantizer output. Also included are a second input circuit that receives the intermediate signal and provides a second quantizer signal and a second quantizer that receives the second quantizer signal and provides a second quantizer output. The first quantizer includes a programmable circuit having a first reference and a negative of the first reference, a first comparator having a first input coupled to the first quantizer signal, a second input coupled to the first reference and a second comparator having a second input coupled to the first quantizer signal a second input coupled to the negative. The first and second comparators have outputs that form the output of the first quantizer.