Clock Domain Timing Calibration for ADC Data Interfaces
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Solution Overview
Problem
The synchronization of digital data between delay and digital domains in wireless communication devices is challenged by the data-dependent variation of the delay domain clock signal, leading to timing errors and potential data loss due to varying phase or duty cycle, particularly in high-performance applications like 5G cellular communications.
Innovation Solution
A circuit and method are introduced that include a clock delay driver with multiple outputs for early and late clock signals, a timing error detection circuit, and a timing loop to adjust the programmable delay of the digital domain clock, ensuring synchronization by detecting and correcting timing errors in real-time or during periodic calibration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the delay domain clock signal is used to interface digital data between clock domains, then data conversion performance is improved, but timing errors occur due to data-dependent phase and duty cycle variations
Solution Approach 1:
A timing error detection circuit monitors the phase and duty cycle variations of the delay domain clock signal relative to the digital domain clock signal. The detection circuit generates error flags that are fed back to a timing loop, which adjusts the delay domain clock timing to correct the detected errors, thereby maintaining reliable synchronization despite data-dependent variations
Solution Approach 2:
A timing error detection circuit is introduced as an intermediary between the delay domain and digital domain clock signals. This circuit monitors timing errors and generates error flags that mediate the synchronization process, allowing the system to detect and correct timing mismatches without directly altering the core data conversion operation
2Measurement precision
If the phase of delay domain clock signal varies with input voltage to enable high performance conversion, then conversion accuracy is improved, but data loss occurs due to timing errors at the interface
Solution Approach 1:
The timing error detection circuit continuously monitors for timing errors that could lead to data loss. When errors are detected (such as doubled or skipped cycles), error flags are generated and fed back to the timing loop, which adjusts the clock timing to prevent further data loss while preserving the voltage-dependent phase variations needed for high accuracy conversion
Solution Approach 2:
The timing loop proactively adjusts the delay domain clock timing based on predicted timing errors from the detection circuit. By cushioning against potential timing errors before they cause data loss, the system maintains both high conversion accuracy and data integrity
3Device complexity
If a fixed delay is used in the digital domain clock to simplify circuit design, then device complexity is reduced, but timing errors cannot be corrected under varying operating conditions
Solution Approach 1:
The fixed delay is replaced with a dynamic, adjustable delay mechanism controlled by the timing loop. The delay amount can be programmatically adjusted based on detected timing errors, allowing the circuit to adapt to varying operating conditions while maintaining relatively simple overall architecture through automated control
Data Source
AI summary
Analog-to-digital converter (ADC) circuitry including a delay domain ADC that outputs converted analog input data along with a delay domain clock. A clock delay driver outputs a digital domain clock, an early clock leading the digital domain clock signal, and a late clock lagging the digital domain clock. An output latch latches the ADC output by the digital domain clock signal. The circuitry includes a timing error detection circuit with inputs receiving the delay domain clock, the early clock, and the late clock. The timing error detection circuit outputs early and late fail flags responsive to detecting timing errors of the digital domain clock relative to the early and late clocks, respectively. Timing loop circuitry has an input coupled to the error flag output of the timing error detection circuitry, and an output coupled to a control input of the clock delay driver.