ADC Lookup Table Segmentation for High-Speed Linearity Correction
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Solution Overview
Problem
High-speed analog-to-digital converters (ADCs) operating at giga samples per second face challenges in correcting non-linearity, which leads to increased power dissipation and area requirements, especially in RF sampling receivers.
Innovation Solution
A circuit and method that utilize a multiplexer, analog-to-digital converter (ADC), and storage circuit to generate and store input codes and output codes in a look-up table, allowing for high-speed operation while reducing memory requirements and power consumption by using a combination of index values and coarse values to represent input codes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a lookup table is used to correct non-linearity in high-speed ADCs, then linearity is improved, but power dissipation and area requirements increase
Solution Approach 1:
The patent segments the input code into two parts: an index value (most significant bits) and a coarse value (least significant bits). Only the index value is used to address the lookup table, while the coarse value is processed separately. This segmentation reduces the lookup table size from requiring storage for all input codes to only requiring storage for index values, thereby reducing power dissipation and area while maintaining linearity correction effectiveness.
Solution Approach 2:
The patent extracts only the necessary portion of the input code (the index value) for lookup table addressing, separating it from the coarse value. This extraction allows the system to use a smaller lookup table that stores correction data only for index values, rather than storing complete input-output mappings for all possible input codes, thus reducing power and area requirements.
2Measurement precision
If a lookup table is used to correct non-linearity in high-speed ADCs, then linearity is improved, but area requirements increase
Solution Approach 1:
The patent segments the input code into an index value and a coarse value, using only the index value to address the lookup table. This segmentation dramatically reduces the lookup table size from needing to store entries for all possible input codes to storing entries only for index values, thereby reducing the area required while maintaining effective linearity correction.
Solution Approach 2:
The patent extracts only the index value portion of the input code for lookup table addressing, separating it from the coarse value. This extraction enables the use of a compact lookup table that requires minimal area while still providing effective non-linearity correction for the high-speed ADC.
3Productivity
If high-speed operation is implemented, then productivity is improved, but non-linearity correction becomes more difficult
Solution Approach 1:
The patent performs preliminary action by pre-calculating and storing correction data in the lookup table during a calibration phase before the high-speed conversion operation begins. During high-speed operation, the system simply retrieves pre-computed correction values using the index value, avoiding complex real-time calculations that would slow down the sampling rate. This preliminary action enables both high productivity and accurate non-linearity correction.
Data Source
AI summary
In described examples, a circuit includes a multiplexer. The multiplexer receives an input voltage and a calibration signal. An analog-to-digital converter (ADC) is coupled to the multiplexer and generates an output code in response to the calibration signal. A storage circuit is coupled to the ADC and stores the input code representative of the calibration signal at an address corresponding to the output code. The stored input code includes an index value and a coarse value.