DTC Gain Calibration with Dynamic Reference Voltage Matching
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Solution Overview
Problem
DTC-based fractional-N phase lock loops face challenges in accurately calibrating DTC gain due to voltage and temperature variations, leading to increased phase noise and spur degradation, as fixed DTC gain values are insufficient and background calibration is compromised by threshold voltage mismatches.
Innovation Solution
A voltage generation circuit dynamically adjusts the reference voltage by generating a voltage output based on the difference between a sampled voltage and a reference voltage, ensuring the comparator threshold voltage matches the Gm circuit threshold voltage, thereby improving DTC gain convergence and reducing phase noise and spur degradation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a fixed DTC gain value is used, then the device complexity is reduced, but the measurement precision of DTC gain calibration deteriorates due to voltage and temperature variations
Solution Approach 1:
The patent implements a dynamic reference voltage adjustment mechanism that automatically adapts to voltage and temperature variations. The system continuously monitors the threshold voltage of the Gm circuit and adjusts the reference voltage accordingly, transforming the static calibration approach into a dynamic one that maintains accuracy under varying operating conditions.
Solution Approach 2:
The patent employs a feedback mechanism where the calibrated DTC gain is used to adjust the reference voltage in subsequent calibration cycles. This closed-loop feedback ensures that the system compensates for drift and variations over time, maintaining high measurement precision without requiring complex manual recalibration procedures.
2Ease of manufacture
If background calibration is performed without threshold voltage matching, then the calibration process is simplified, but the reliability of DTC gain calibration deteriorates due to threshold voltage mismatches
Solution Approach 1:
The system performs self-calibration by automatically detecting and compensating for threshold voltage mismatches between the comparator and Gm circuit. The calibration circuit autonomously adjusts the reference voltage to match the Gm circuit threshold, eliminating the need for manual intervention while ensuring high calibration reliability.
Solution Approach 2:
The patent changes the reference voltage parameter dynamically during calibration to match the Gm circuit threshold voltage. By adjusting this key parameter based on actual circuit characteristics rather than fixed design values, the system achieves reliable calibration despite process variations and temperature effects.
3Ease of operation
If the reference voltage is not dynamically adjusted, then the device operation is simpler, but the phase noise performance deteriorates due to inaccurate DTC gain calibration
Solution Approach 1:
The system performs preliminary calibration to determine the accurate DTC gain value before normal PLL operation begins. This pre-calibration step establishes the correct reference voltage offset that compensates for threshold mismatches, ensuring low phase noise performance from the start without requiring continuous complex adjustments during operation.
Solution Approach 2:
The calibrated reference voltage is fed back into the calibration circuit to maintain accuracy over time. This feedback mechanism ensures that the reference voltage remains properly adjusted despite aging, temperature drift, or process variations, consistently maintaining low phase noise without requiring frequent manual recalibration.
4Ease of operation
If the reference voltage is not dynamically adjusted, then the device operation is simpler, but the spur performance deteriorates due to inaccurate DTC gain calibration
Solution Approach 1:
The system performs preliminary calibration to establish the accurate DTC gain and corresponding reference voltage offset before fractional-N operation begins. This pre-calibration ensures that the DTC is properly compensated for threshold voltage mismatches, minimizing fractional spur generation from the outset without requiring complex runtime adjustments.
Solution Approach 2:
The patent adjusts the reference voltage parameter based on the calibrated DTC gain to optimize spur performance. By changing this parameter to match actual circuit characteristics rather than using fixed design values, the system achieves low fractional spur levels while maintaining simple operation during normal use.
Data Source
AI summary
A system and method for fast converging gain calibration for phase lock loops (PLL) are herein disclosed. According to one embodiment, a method includes receiving, with a voltage generation circuit, an input value representing a difference between a sampled voltage and a reference voltage, and adjusting, with the voltage generation circuit, the reference voltage by generating a voltage output based on the difference represented by the input value.