Nonlinear ADC Loop for PSI5 and WSS Accuracy With Less Silicon

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Solution Overview

Problem

Existing analog-to-digital converters for PSI5 and WSS systems face challenges in achieving high accuracy and reduced silicon area occupation while maintaining fast conversion and robust noise rejection, particularly due to the need for sample and hold circuits and complex high-pass filters.

Innovation Solution

An innovative analog-to-digital conversion loop with a nonlinear input-output conversion characteristic, utilizing a logarithmic analog-to-digital converter and a digital integrator, which eliminates the need for a sample and hold circuit and reduces silicon area, achieving accurate conversions in quasi-steady-state conditions and fast transient responses.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If a linear flash analog-to-digital converter is used to achieve high accuracy conversion, then measurement precision is improved, but device complexity and silicon area occupation increase exponentially with the number of bits

Engineering Contradiction:

Improveconversion accuracyVSAvoidconverter architecture complexity

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The patent transforms the linear conversion characteristic into a nonlinear one, specifically using a logarithmic transfer function. This parameter change in the conversion characteristic allows the system to achieve high measurement precision for small error signals while keeping the device complexity manageable through the mathematical properties of logarithmic functions.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The conversion process is segmented into two distinct stages: a coarse conversion stage that handles large error signals with larger quantization steps, and a fine conversion stage that handles small error signals with smaller quantization steps. This segmentation allows the system to achieve high overall precision without requiring a full-resolution converter across the entire signal range.

Inventive Principle:

Principle #1Segmentation

2Measurement precision

If a sample and hold circuit is added to maintain accuracy during signal variations, then measurement precision is improved, but device complexity and conversion time increase

Engineering Contradiction:

Improveconversion accuracy during signal variationsVSAvoidconversion time

Core Design Contradiction:

Measurement precisionVSLoss of time

Solution Approach 1:

The patent implements a dynamic quantization step size that automatically adjusts based on the magnitude of the error signal. When the error signal is large, a larger quantization step is used for faster response; when the error signal is small, a smaller quantization step is used for higher precision. This dynamic adaptation eliminates the need for sample and hold circuits while maintaining both speed and accuracy.

Inventive Principle:

Principle #15Dynamics

3Ease of manufacture

If uniform quantization steps are used throughout the conversion range, then manufacturing precision is simplified, but measurement precision deteriorates for small error signals

Engineering Contradiction:

Improveconverter design simplicityVSAvoidprecision for small error signals

Core Design Contradiction:

Ease of manufactureVSMeasurement precision

Solution Approach 1:

The patent applies different quantization characteristics to different regions of the error signal range. For small error signals (near zero), a fine quantization step is used to achieve high precision. For large error signals, a coarser quantization step is used. This local differentiation of quantization quality optimizes measurement precision where it matters most while maintaining manufacturing feasibility.

Inventive Principle:

Principle #3Local quality

4Speed

If a high-pass filter is inserted in the direct path to achieve fast transient response, then speed is improved, but device complexity and noise sensitivity increase

Engineering Contradiction:

Improvetransient response speedVSAvoidfilter circuit complexity

Core Design Contradiction:

SpeedVSDevice complexity

Solution Approach 1:

The patent replaces the need for analog high-pass filter circuits with a digital-domain solution. The nonlinear analog-to-digital converter with adaptive quantization inherently provides fast transient response through its ability to use larger quantization steps during transient conditions, eliminating the need for separate filter hardware and its associated complexity and noise sensitivity.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Data Source

PatentUS8872682B2Analog-to-digital conversion loop for PS15 and WSS systems

Publication Date: 2014.10.28 STMICROELECTRONICS INT NV

AI summary

An analog-to-digital conversion loop adapted to generate a digital output signal corresponding to a low-pass filtered replica of an analog input signal, including an analog adder configured to receive the input analog signal and an analog feedback signal, adapted to generate an analog error signal corresponding to the difference between the analog input signal and the analog feedback signal; an analog-to-digital converter having a nonlinear input-output conversion characteristic defining a larger quantization step the more the input to be converted differs from a null value, configured to receive the analog error signal and to generate a corresponding digital error signal a digital integrator configured to receive the digital error signal, configured to generate the digital output signal corresponding to the time integration of the digital error signal; a digital-to-analog converter, configured to receive the digital output signal and to generate the analog feedback signal as analog replica of the digital output signal.