DCXO Capacitor Array Self-Test Using Row-Level DEM Screening
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Solution Overview
Problem
Testing large capacitor arrays in digitally controlled crystal oscillators (DCXO) is impractically time-consuming and costly due to the need to test each individual capacitor, and failed capacitors can cause nonlinearity in output frequency, making it difficult to identify and correct issues.
Innovation Solution
Implementing dynamic element matching (DEM) during regular operation of the DCXO, allowing capacitors to be tested in rows as single entities rather than individually, which reduces testing time and identifies failures by analyzing row-level frequency characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If each individual capacitor in the matrix is tested, then measurement precision is improved, but testing time increases to more than an hour
Solution Approach 1:
The patent merges the testing of multiple capacitors by grouping them into rows, where each row is tested as a single unit rather than testing each capacitor individually. This combining approach reduces the total number of tests required while maintaining adequate measurement precision through the aggregated signal.
Solution Approach 2:
The patent segments the capacitor matrix into row groups, where capacitors are organized in a matrix structure with rows and columns. By segmenting the testing into row-based groups rather than individual capacitor tests, the system reduces testing complexity and time while maintaining measurement accuracy.
2Adaptability or versatility
If a large matrix of capacitors is used for tuning, then tuning range is improved, but device complexity increases
Solution Approach 1:
The capacitor array is segmented into rows and columns with row and column decode circuits that control groups of capacitors. This segmentation allows for systematic control and testing of large numbers of capacitors while managing complexity through organized structure and hierarchical control.
Solution Approach 2:
The row and column decode circuits serve multiple functions: they control which capacitors are activated for tuning and also facilitate the testing mechanism by enabling row-based selection and evaluation. This multi-functionality reduces overall system complexity despite the large number of capacitors.
3Reliability
If individual capacitor testing is performed, then reliability is improved, but ease of operation deteriorates due to testing complexity
Solution Approach 1:
The testing operation merges multiple capacitor evaluations into row-based tests, where the state of an entire row is determined by a single test result. This combining approach maintains reliability assessment while dramatically simplifying the ease of operation by reducing the number of test operations required.
Data Source
AI summary
A novel testing mechanism operative to test large capacitor arrays such as those used in a digitally controlled crystal oscillator (DCXO). The invention is adapted for use in DCXO circuits that employ dynamic element matching in their array decoding circuits. The invention combines the use of DEM during regular operation of the DCXO with a testing technique that greatly reduces the number of tests required. The invention tests the capacitors in the array on a row by row, wherein all the capacitors in a row are tested lumped together and treated as a single entity, which results in significantly reduced testing time. This permits the measurement of significantly higher frequency deviations due to the larger capacitances associated with an entire row of capacitors being tested.