Audio Codec BIST Using Dual-Channel DFT Without DSP Core
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Solution Overview
Problem
Conventional audio codec testing methods require expensive external equipment and complex setups, and existing self-test methods are limited in scope and increase chip area and cost due to the need for a built-in DSP core.
Innovation Solution
A built-in self-test (BIST) method using discrete Fourier transform (DFT) calculations, performed by dual channels of the audio codec's DAC and ADC, eliminates the need for a DSP core and external testing equipment, allowing for cost-effective and efficient self-testing during mass production.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Extent of automation
If a DSP core is built-in for self-testing, then testing capability is improved, but chip area and cost increase
Solution Approach 1:
The patent extracts the DFT calculation function from a DSP core and implements it using only the existing DAC and ADC channels of the audio codec. This removes the need for a separate DSP core while maintaining self-testing capability, directly resolving the contradiction between automation and chip area.
Solution Approach 2:
The patent makes the DAC and ADC channels perform multiple functions: they serve both as audio processing components and as test signal generation/analysis components. By using the same hardware resources for both audio functionality and self-testing, the need for additional dedicated test hardware is eliminated.
2Measurement precision
If external mixed-signal test equipment is used, then testing accuracy is improved, but equipment cost and setup complexity increase
Solution Approach 1:
The audio codec performs self-testing using its own internal resources (DAC, ADC, and existing processing channels). The device serves itself by generating test signals, performing conversions, and analyzing results without requiring external test equipment, thereby eliminating setup complexity while maintaining measurement capability.
Solution Approach 2:
The patent combines the test signal generation, conversion, and analysis functions into the existing audio processing path. By merging testing operations with the audio codec's normal operation channels, the system achieves accurate measurements without requiring separate external test equipment.
3Productivity
If DSP core is used for DFT calculation, then calculation speed is improved, but chip cost increases
Solution Approach 1:
The patent replaces the expensive DSP core with a simpler, lower-cost implementation using basic DAC and ADC operations. While a DSP core would provide faster calculation, this approach uses readily available, lower-cost components that achieve sufficient calculation speed for the application, reducing overall chip cost.
Data Source
AI summary
An audio codec and a BIST method adapted for the audio codec are provided. The BIST method includes the following steps. A first channel digital-to-analog converter (DAC) of the audio codec converts a test signal into an analog signal. A first channel analog-to-digital converter (ADC) of the audio codec converts the analog signal into a digital signal. Use a second channel DAC of the audio codec and a second channel ADC of the audio codec to calculate the magnitudes of a plurality of spectral components of the DFT of the digital signal. Determine whether the audio codec passes the test according to the magnitudes of the spectral components.