Online DTC Gain Calibration Using a Comparator Reference Path
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Solution Overview
Problem
Existing methods for recalibrating the gain of digital-to-time converters (DTCs) during operation are challenging due to low probability of the DTC code being zero, leading to increased jitter and degradation of performance, which is problematic for applications with stringent jitter requirements.
Innovation Solution
A system and method for gain calibration of DTCs using a calibration DTC and a latch comparator to align output signals, adjusting the calibration DTC code to minimize time differences, and using an average computation module to determine the gain error, allowing calibration at near-zero and near-full code values.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If existing recalibration methods are used when DTC code is zero, then gain calibration can be performed, but the probability of DTC code being zero is very low (0.00024 for 12-bit code), making calibration rare and ineffective
Solution Approach 1:
The patent introduces a calibration DTC that performs calibration operations in advance or independently from the main DTC operation. The calibration DTC can be configured to generate specific code values (including zero and other test patterns) proactively, rather than waiting for the main DTC to naturally produce these codes. This preliminary action ensures calibration opportunities are created regardless of the main DTC's operational state.
Solution Approach 2:
The patent uses a calibration DTC as an intermediary device that facilitates gain calibration without directly interfering with the main DTC's normal operation. The calibration DTC acts as a mediator by generating calibration signals that can be compared with the main DTC output, enabling indirect measurement and adjustment of gain parameters without requiring the main DTC to enter specific code states.
2Reliability
If recalibration methods are used during operation, then gain error can be compensated, but jitters increase in the output, degrading DTC performance
Solution Approach 1:
The patent segments the DTC system into a main operational DTC and a separate calibration DTC. This segmentation allows calibration functions to be performed independently from the main signal path. The calibration DTC processes calibration codes separately, and its output is used only for measurement and adjustment purposes, not for the primary time-critical signal generation, thus isolating jitter-inducing calibration operations from the main output.
Solution Approach 2:
The patent creates a copy of the DTC structure (the calibration DTC) that replicates the essential functionality needed for calibration. This copy can be configured to generate specific output patterns for calibration purposes without affecting the original DTC's performance-critical operations. The calibration DTC serves as a test duplicate that enables gain measurement and adjustment while leaving the main system untouched.
3Duration of action of stationary object
If DTC operates uninterrupted for several years, then continuous operation is maintained, but analog impairments occur causing gain deviations due to aging
Solution Approach 1:
The patent implements a feedback mechanism where the output of the calibration DTC is continuously monitored and compared with expected values. The latch comparator detects deviations between calibration output and reference signals, and this feedback information is used to adjust the calibration DTC code, thereby compensating for gain drift caused by aging. This closed-loop feedback enables long-term reliability by continuously correcting age-related degradations.
Solution Approach 2:
The calibration DTC performs self-calibration by automatically adjusting its own code based on feedback from the latch comparator. The system uses itself (the calibration DTC) to measure and correct its own gain errors without requiring external intervention or manual recalibration. This self-service capability enables the system to maintain accuracy over extended periods by autonomously compensating for aging effects.
Data Source
AI summary
A system includes a first digital-to-time converter (DTC) adapted to receive a first DTC code and a first clock signal. The first DTC provides an output clock signal. The system includes a calibration DTC adapted to receive a calibration DTC code and a second clock signal. The calibration DTC provides a calibration output signal. The system includes a latch comparator which provides outputs indicative of which of the output clock signal and the calibration output signal is received first. The system includes an average computation module which provides an average value of the outputs of the latch comparator. The system includes a digital controller adapted to receive the average value. The digital controller provides the DTC code and the calibration DTC code.