Clock Path Architecture for Low-Power Phase Alignment
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Solution Overview
Problem
High-speed wireline transmitters face challenges in optimizing performance and power consumption, particularly in achieving accurate clock alignment and considering process-voltage-temperature (PVT) variations, which can lead to power penalties and data corruption.
Innovation Solution
A clock path architecture for an interleaved transmitter using a multiplexer-based phase sampler with a bootstrap switch, an average duty cycle sensor, and a clock-to-data phase detector, which enables sub-unit interval alignment and optimal duty cycle tracking, reducing power consumption and improving jitter and Signal-to-Noise-and-Distortion Ratio (SNDR).
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional clock alignment circuits are used in high-speed wireline transmitters, then clock alignment can be achieved, but power consumption increases and performance is degraded due to sensor loading on the clock network
Solution Approach 1:
The patent introduces an intermediary buffer stage between the clock network and the phase alignment circuits. This buffer acts as a mediator that isolates the sensor loading from the clock network, allowing accurate phase detection without directly loading the clock signals. The buffer absorbs the loading effect while maintaining clock signal integrity, thus resolving the contradiction between achieving accurate clock alignment and minimizing power consumption.
Solution Approach 2:
The patent creates a copy of the clock signal through the buffer stage rather than directly sensing the original clock network. The buffer generates a replicated clock signal that can be safely monitored and adjusted without affecting the primary clock distribution network. This copying approach enables phase alignment measurements while preventing sensor loading from degrading the original clock signals.
2Measurement precision
If sensor loading is applied to detect phase errors, then phase alignment can be achieved, but the clock network performance deteriorates due to loading effects
Solution Approach 1:
The buffer stage serves as an intermediary that enables phase error detection without directly loading the clock network. It provides a isolated sensing point where phase measurements can be taken accurately while the buffer isolates these measurement circuits from the main clock distribution network, preventing loading effects from degrading clock signal quality.
3Reliability
If process-voltage-temperature variations are compensated for accurate alignment, then data integrity is improved, but device complexity increases
Solution Approach 1:
The patent implements feedback mechanisms where phase error detectors continuously monitor clock phase relationships and feed this information back to control circuits. These control circuits adjust delay elements in real-time to compensate for PVT variations. The feedback loop automatically adapts to changing conditions without requiring complex manual calibration, maintaining data integrity while managing device complexity through automated control.
Solution Approach 2:
The patent incorporates preliminary calibration and initialization routines that establish baseline phase relationships before normal operation. Delay elements are pre-configured with initial values that account for expected PVT ranges, and the system performs self-adjustment during startup. This preliminary action reduces the complexity of continuous compensation during operation by establishing a known good state beforehand.
Data Source
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AI summary
A data transmitter with a phase detector, average duty cycle sensor and phase sampler to optimize a clock/data paths. Phase and duty cycle information are provided to a digital control to adjust a timing in the data path and clock path, respectively. The phase detector reads a skew between the data and negative and positive phase clock signals inside a driver. An optimal pulse width delta is determined by the target duty cycle sensor. Using a measured averaged duty cycle sensor, the digital control calculates the duty cycle error to the target value that is needed inside the driver. The phase sampler has a multiplexer which routes the clock signals to phase sensors which determine a phase error based on, e.g., a rising edge-to-rising edge comparison and a falling edge-to-falling edge comparison. In addition, it includes a duty cycle sensor for each clock phase.