Lookahead Pipelined ADC With Open-Loop Residue Amplifier Calibration
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Solution Overview
Problem
High-speed analog-to-digital converters (ADCs) face challenges in achieving both high speed and high accuracy while minimizing power consumption, particularly for 10 Gbit/s serial data transmission applications, as existing technologies consume excessive power and have limitations in offset requirements and comparator metastability.
Innovation Solution
The implementation of a lookahead pipelined ADC architecture using open-loop residue amplifiers with calibration, which reduces power consumption and increases sampling rate by eliminating the need for linear amplifiers, and incorporates redundancy and digital calibration to compensate for non-linearity and errors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional closed-loop residue amplifiers are used in pipeline ADC stages, then linearity and accuracy are improved, but power consumption increases significantly
Solution Approach 1:
The patent extracts and removes the feedback loop from the residue amplifier configuration, transitioning from a closed-loop operational amplifier to an open-loop amplifier. This extraction of the feedback mechanism eliminates the associated power consumption while maintaining the essential amplification function through alternative means such as calibration and redundancy.
Solution Approach 2:
The patent changes the operating parameters of the residue amplifier by removing the feedback connection, fundamentally altering the amplifier's behavior from a controlled closed-loop system to an uncontrolled open-loop system. This parameter change (from closed to open loop) reduces power consumption while requiring compensating mechanisms for linearity.
2Use of energy by moving object
If open-loop residue amplifiers are used to reduce power consumption, then power efficiency is improved, but non-linearity and offset errors increase
Solution Approach 1:
The patent applies preliminary calibration actions to characterize and compensate for the non-linearities and offset errors of open-loop amplifiers before they are used in the ADC conversion process. By pre-measuring and storing correction data, the system compensates for the inherent imperfections of open-loop operation without requiring complex real-time correction circuits.
Solution Approach 2:
The patent introduces a digital feedback mechanism where the output of the open-loop amplifier is compared with expected values, and correction signals are generated to compensate for non-linearities. This digital feedback loop restores accuracy without requiring an analog feedback connection that would increase power consumption.
3Speed
If flash ADC architecture is used to achieve high speed conversion, then conversion speed is improved, but device complexity and power consumption increase geometrically with resolution
Solution Approach 1:
The patent segments the high-speed conversion task into multiple lower-resolution pipeline stages, each handling a portion of the total conversion. Instead of using a single flash converter with 2^N-1 comparators for N-bit resolution, the system divides the conversion into sequential stages, each with fewer comparators, thereby reducing overall complexity while maintaining high throughput.
Solution Approach 2:
The patent transitions from the temporal dimension (single high-speed flash conversion) to the spatial dimension by adding multiple pipeline stages that operate concurrently on different data samples. This dimensional change allows parallel processing of multiple inputs, achieving high effective conversion rate without requiring geometrically increasing numbers of comparators.
4Measurement precision
If higher resolution flash ADCs are implemented to improve accuracy, then measurement precision is improved, but offset requirements become tighter and power consumption increases
Solution Approach 1:
The patent applies preliminary offset calibration and characterization to each comparator and amplifier stage before operation. By pre-measuring and storing offset values, the system compensates for manufacturing variations without requiring extremely tight matching during fabrication, thereby achieving high resolution with relaxed manufacturing tolerances.
Solution Approach 2:
The patent uses digital copies and models of the analog component characteristics to compensate for physical imperfections. By creating digital representations of offset and gain errors through calibration, the system can correct these errors in the digital domain, eliminating the need for high-precision analog matching.
Data Source
AI summary
A lookahead pipelined ADC architecture uses open-loop residue amplifiers with calibration. This approach is able to achieve a high-speed, high-accuracy ADC with reduced power consumption. In one aspect, an ADC pipeline unit includes a plurality of lookahead pipeline stages (i.e., an ADC lookahead pipeline) coupled to a calibration unit. The ADC lookahead pipeline uses open-loop residue amplifiers. The calibration unit compensates for non-linearity in the open-loop amplifiers.