PLL Self-Testing via Pseudo-Random Phase Noise Correlation
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Solution Overview
Problem
Self-testing of phase-locked loop (PLL) parameters in integrated circuits is challenging due to the need for maintaining performance within specific limits over the circuit's lifetime, especially in applications requiring compliance with standards that mandate continuous monitoring and detection of faults like Single Event Upsets (SEUs).
Innovation Solution
Incorporating pseudo-random noise into the PLL's input signal to self-test PLL parameters by cross-correlating the output signal with the noise, allowing for continuous monitoring and assessment of performance levels, including phase margin and impulse response, which can trigger actions such as error messages or system reboot if failures are detected.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional production testing methods are used for PLL parameters, then initial performance can be verified, but continuous monitoring and detection of faults over the circuit's lifetime cannot be achieved
Solution Approach 1:
The PLL system performs self-testing by injecting pseudo-random noise into its own input signal and correlating the output with the injected noise. The phase detector output is cross-correlated with the injected pseudo-random sequence to extract impulse response and phase margin information, enabling the circuit to monitor its own health without external testing equipment.
Solution Approach 2:
The self-testing mechanism operates continuously during normal PLL operation by injecting pseudo-random noise into the reference clock signal. This allows uninterrupted monitoring of PLL parameters (phase margin, impulse response) throughout the circuit's lifetime, enabling real-time detection of drift or faults caused by aging, temperature, or radiation effects.
2Reliability
If PLL parameters are monitored continuously to detect faults like SEUs, then reliability and safety compliance are improved, but the complexity of the monitoring system increases
Solution Approach 1:
The pseudo-random noise injection mechanism serves multiple functions: it acts as a test stimulus, a dither signal to linearize the phase detector, and a correlation reference for extracting impulse response. The same hardware components (phase detector, correlation circuit) are used for both normal PLL operation and self-testing, eliminating the need for separate dedicated test equipment.
Solution Approach 2:
The system monitors changes in key PLL parameters (phase margin, impulse response characteristics) over time by continuously performing cross-correlation measurements. When these parameters deviate from acceptable ranges or show trends indicating degradation, the system can detect faults such as Single Event Upsets and trigger appropriate responses.
3Productivity
If pseudo-random noise is injected into the PLL input signal for self-testing, then continuous parameter monitoring is enabled, but additional signal processing complexity is introduced
Solution Approach 1:
The patent replaces traditional mechanical or external electrical testing methods with a digital signal processing approach using pseudo-random sequences and cross-correlation. Instead of applying external test equipment and manually analyzing results, the system uses mathematical correlation of the phase detector output with the injected pseudo-random sequence to automatically extract impulse response and phase margin information.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Enables continuous, efficient self-testing of PLL parameters during operation, detecting faults and maintaining performance within specified limits, thus ensuring compliance with safety standards and extending the lifespan of safety-sensitive integrated circuits.
Implementation Method 1
The correlation circuit self-tests the PLL by cross-correlating a signal corresponding to the output signal from the phase detector with the pseudo-random noise and by assessing results of the cross-correlation relative to a known threshold indicative of a performance level of the PLL
Implementation Method 2
The input application clock signal can be phase modulated to generate the reference clock signal, as input to the PLL, that carries the pseudo-random phase noise
Data Source
AI summary
An apparatus includes signal control circuitry, a phase-locked loop (PLL), and a correlation circuit. The signal control circuitry provides a reference clock signal carrying pseudo-random phase noise and as derived from an application clock signal and pseudo-random noise. The PLL, responsive to the reference clock signal carrying the pseudo-random phase noise, provides an output signal that is related to the phase of the reference clock signal. The correlation circuit self-tests the PLL by cross-correlating a signal corresponding to the output signal from the phase detector with the pseudo-random noise and, in response, by assessing results of the cross-correlation relative to a known threshold indicative of a performance level of the PLL.