Gated Ring Oscillator TDC Calibration for Nonlinear Time Measurement
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Solution Overview
Problem
Gated ring oscillators (GRO) based time-to-digital converters (TDCs) face non-linearities in measurement results due to power supply ripples, leading to increased errors over time, which affect the accuracy of time measurements in applications like phase locked loops (PLLs).
Innovation Solution
A method is introduced to determine and correct non-linearities in GRO-based TDCs by using a series of programmed pulses to establish a non-linearity model, which is applied during calibration to generate corrected measurement results, mitigating the effects of power supply ripples and temperature variations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a gated ring oscillator based TDC is used to measure time, then a large conversion range with multiple bits output is achieved, but non-linearities in measurement results occur due to power supply ripples causing increased errors over time
Solution Approach 1:
The patent applies preliminary action by performing calibration measurements before actual time measurements to characterize and store non-linearity correction data. The TDC is calibrated at multiple known time points to establish a non-linearity model that is stored and later applied to correct measurement results, preventing accuracy degradation over time.
Solution Approach 2:
The patent implements feedback by using the calibration data to generate correction values that are applied to subsequent measurements. The system continuously references the stored non-linearity model to adjust and correct measurement outputs, ensuring accuracy is maintained throughout the conversion range.
2Use of energy by moving object
If GRO draws non-constant pulse-like current from power supply, then time savings and power consumption benefits are achieved, but ripple is caused in power supply causing response time variation
Solution Approach 1:
The patent substitutes the mechanical/electrical problem of power supply ripple with a data processing solution. Instead of modifying the GRO current draw, the system measures the effect through calibration and corrects it through digital processing using non-linearity models, replacing physical stabilization with computational correction.
3Measurement precision
If calibration is performed to determine non-linearity model, then measurement accuracy is improved, but additional calibration time and processing is required
Solution Approach 1:
The calibration process is performed as a preliminary action during initialization or setup phases, separating the time-consuming accuracy improvement from the actual measurement operations. This allows the system to undergo detailed calibration once, then use the stored model for rapid corrections during normal operation.
Solution Approach 2:
The system performs calibration at a sufficient number of points to accurately characterize non-linearity across the full conversion range, using more calibration points than the minimum necessary to ensure the correction model remains valid throughout the entire measurement range.
Data Source
AI summary
Aspects of the disclosure provide for an apparatus comprising a time-to-digital converter (TDC) and a processor coupled to the TDC. In some examples, the TDC may be configured to receive a signal and generate a measurement result indicating a time between start and stop events of the signal. The processor may be configured to receive the measurement result, compare the measurement result to a target value, and determine a non-linearity model configured to correct a variance of the measurement result from the target value.