TI-ADC Timing Calibration Using Sample Correlation Feedback
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Solution Overview
Problem
Data distortion occurs due to timing errors, specifically time skews, between analog-to-digital converters in high-speed analog-to-digital conversion operations for high-frequency signals, which deteriorates the performance of analog-to-digital conversion circuits.
Innovation Solution
An analog-to-digital conversion circuit that includes a plurality of analog-digital converters operating in a time-interleaving manner, a timing calibrator that calculates calibration values and time skews based on correlation values between target samples and adjacent samples, and a clock phase adjuster that adjusts clock signal phases to correct time skews.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If multiple ADCs operate in time-interleaving manner to increase sampling frequency, then conversion speed is improved, but time skew between ADCs causes data distortion and performance deterioration
Solution Approach 1:
The patent implements a feedback mechanism where the timing calibrator continuously monitors correlation values between samples from multiple ADCs, calculates time skew, and generates calibration codes that are fed back to adjust the sampling timing of each ADC. This closed-loop feedback system dynamically compensates for time skew variations, maintaining conversion accuracy while enabling high-speed time-interleaved operation.
Solution Approach 2:
The patent dynamically adjusts the sampling timing parameter (phase) of each ADC based on calculated time skew values. By changing the timing parameter of each ADC's sampling clock according to its specific skew, the system compensates for timing errors and restores accurate time-interleaved sampling without reducing the overall sampling frequency.
2Measurement precision
If time skew calibration is performed using auto-correlation operation, then timing accuracy is improved, but conversion operation must be interrupted
Solution Approach 1:
The patent enables continuous time skew calibration by performing auto-correlation operations on samples that are already being processed during normal conversion operation. The timing calibrator operates concurrently with the ADCs, using available sample data to calculate correlation values and update calibration codes without interrupting the analog-to-digital conversion process, thus maintaining continuous useful action.
Solution Approach 2:
The system performs self-calibration by automatically calculating time skew from its own operating samples and adjusting its own timing parameters. The calibration process uses the actual sample data generated during conversion operation, allowing the system to self-correct timing errors without external intervention or interruption of the conversion process.
3Reliability
If the number of ADCs is increased to satisfy Nyquist frequency for high-bandwidth signals, then conversion performance is improved, but device complexity and time skew calibration difficulty increase
Solution Approach 1:
The timing calibrator is designed as a universal calibration unit that can handle any number of ADCs in the time-interleaved configuration. It calculates correlation values between samples from multiple ADCs and generates individual calibration codes for each ADC, providing a scalable solution that works for 2 ADCs or any larger number, thus managing complexity through a unified multi-functional approach.
Data Source
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AI summary
A analog-to-digital conversion circuit includes a plurality of time interleaved analog-digital converters (TI-ADCs), a timing calibrator configured to calculate calibration values of the plurality of TI-ADCs based on correlation values between target samples output from target TI-ADCs and adjacent samples of adjacent TI-ADCs in two respective cycles and output codes for calibrating time skews of the plurality of TI-ADCs based on the calibration values and a plurality of calibration parameters, and a clock phase adjuster configured to adjust phases of a plurality of clock signals based on the codes.