CTDS ADC On-Chip Test Circuit Using FIR DAC Signals

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Solution Overview

Problem

Testing of continuous time delta sigma (CTDS) analog-to-digital converters (ADCs) within integrated circuits is challenging due to the difficulty in generating an analog test signal on-chip, which is essential for efficient and cost-effective validation of ADC accuracy, especially in complex System on-Chip (SoC) or System in Package (SiP) environments where external access is limited.

Innovation Solution

A test circuit within the integrated circuit generates an analog test signal by converting multibit digital reference data into a single bit data stream using a finite impulse response (FIR) digital-to-analog converter (DAC), which is then used to test the CTDS ADC, allowing for on-chip testing and comparison with digital reference data to determine accuracy.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If external automated test equipment is used for testing ADCs, then testing accuracy can be maintained, but testing cost and complexity increase significantly

Engineering Contradiction:

ImproveADC testing accuracyVSAvoidtesting system complexity

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The patent extracts the test signal generation function from external test equipment and implements it within the integrated circuit itself using a digital-to-analog converter and signal generator. This removes the need for complex external analog signal generation equipment while maintaining testing accuracy through on-chip signal generation and comparison.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The patent introduces a digital intermediary approach by converting the test signal to digital form within the chip, processing it through digital circuits, and comparing digital outputs. This digital intermediary eliminates the need for complex external analog testing infrastructure while preserving measurement accuracy through digital signal processing and comparison.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Device complexity

If on-chip test signal generation is implemented, then testing cost and complexity are reduced, but generating a reliable analog test signal becomes difficult

Engineering Contradiction:

Improvetesting system complexityVSAvoidanalog test signal generation difficulty

Core Design Contradiction:

Device complexityVSEase of manufacture

Solution Approach 1:

The patent replaces the mechanical/analog approach of generating test signals with a digital approach. A digital-to-analog converter generates the analog test signal from digital data stored in memory, and a digital signal processor controls the generation process. This substitution makes the system easier to manufacture and program while maintaining signal reliability.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent changes the fundamental parameter of signal generation from analog circuit design to digital data processing. By storing test signal parameters as digital data in memory and converting them to analog form on-demand, the system achieves flexibility and reliability without the complexity of analog signal generation circuits.

Inventive Principle:

Principle #35Parameter changes

3Measurement precision

If functional specification testing with external equipment is used, then ADC accuracy can be validated, but access to internal subsystems becomes problematic in complex SoC

Engineering Contradiction:

ImproveADC accuracy validationVSAvoidaccess to internal subsystems

Core Design Contradiction:

Measurement precisionVSEase of operation

Solution Approach 1:

The patent merges the test signal generation, signal processing, and result comparison functions into a single on-chip integrated system. The digital-to-analog converter, signal generator, ADC under test, and comparator are all integrated within the same chip, eliminating the need for external equipment and providing direct access to internal subsystems for accurate ADC validation.

Inventive Principle:

Principle #5Merging (Combining)

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

This approach enables efficient and effective on-chip testing of CTDS ADCs, reducing testing costs and complexity by generating a reliable analog test signal internally, thereby improving the accuracy assessment of ADCs without the need for external devices.

Implementation Method 1

converting, with a finite impulse response digital-to-analog converter of the integrated circuit, the single bit data stream to an analog test signal

Methodology Applied

Scientific EffectDigital-to-Analog Conversion:

Implementation Method 2

converting, with a continuous time delta sigma analog-to-digital converter of the integrated circuit, the analog test signal to digital test data

Methodology Applied

Scientific EffectAnalog-to-Digital Conversion:

Data Source

PatentUS11901919B2On chip test architecture for continuous time delta sigma analog-to-digital converter

Publication Date: 2024.02.13 STMICROELECTRONICS INT NV

AI summary

An integrated circuit includes a continuous time delta sigma analog-to-digital converter (CTDS ADC) and a test circuit for testing the CTDS ADC. The test circuit converts multi-bit digital reference data to a single-bit digital stream. The test circuit then passes the single-bit digital stream to a finite impulse response digital-to-analog converter (FIR DAC). The FIR DAC converts the single-bit digital stream to an analog test signal. The analog test signal is then passed to the CTDS ADC. The CTDS ADC converts the analog test signal to digital test data. The test circuit analyzes the digital test data to determine the accuracy of the CTDS ADC.