PHY Data Alignment Using Phase Interpolator and CDRLF
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Solution Overview
Problem
Traditional data alignment methods in PHY devices introduce significant latency due to the need for deskewing operations using FIFO structures, which are inefficient in aligning sampler clocks with received serial data.
Innovation Solution
A clock data recovery loop filter (CDRLF)-based data alignment system that uses a phase interpolator to align sampler clocks optimally relative to received high-speed data, performing initial lock calibration and fine adjustments to ensure the first bit of parallel data is aligned correctly, thereby reducing latency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional FIFO structures are used for deskewing operations, then data alignment is achieved, but significant latency is introduced
Solution Approach 1:
The patent extracts the alignment information (first bit position detection) from the data stream and processes it separately through a feedback mechanism. The system detects where the first bit appears in parallel bit positions, extracts this alignment information, and uses it to adjust sampler clock phases without requiring data to wait in FIFO buffers, thereby achieving alignment with minimal latency.
Solution Approach 2:
The patent implements a feedback mechanism where the receiver detects the position of the first bit in the received parallel data, determines the required phase adjustment, and sends control signals back to the transmitter to adjust the sampler clock phases. This closed-loop feedback system enables dynamic alignment adjustment without introducing the latency associated with FIFO-based deskewing.
2Productivity
If sampler clocks are not aligned optimally, then data transmission continues, but sampling precision deteriorates
Solution Approach 1:
The patent makes the sampler clock phases dynamic and adjustable rather than fixed. The system continuously monitors the position of the first bit and dynamically adjusts the phase of sampler clocks based on detected alignment requirements. This dynamic adjustment ensures that sampling remains precisely aligned with incoming data transitions while maintaining continuous data transmission.
Solution Approach 2:
The patent changes the phase parameter of sampler clocks based on detected alignment conditions. When misalignment is detected (first bit not in expected position), the system modifies the phase parameter of the sampler clocks to correct the timing, thereby maintaining optimal sampling precision without interrupting the data transmission process.
3Loss of information
If first bit position detection is implemented, then alignment information is obtained, but system complexity increases
Solution Approach 1:
The patent performs preliminary detection of the first bit position immediately upon receiving data. By detecting the alignment information as early as possible in the data reception process, the system obtains necessary alignment data without requiring complex continuous monitoring mechanisms. This preliminary detection approach simplifies the overall system while effectively recovering alignment information.
Data Source
AI summary
A physical layer (PHY) device comprises a phase interpolator to generate a set of sampler clocks. A sampler of the PHY device samples a calibration data pattern based on the set of sampler clocks. A data alignment system of the PHY device performs a coarse calibration and a fine calibration on the sampler clock signals. During the coarse calibration, the data alignment system moves the sampler clock signals earlier or later in time relative to the sampled data based on a first bit of the sampled data. During the fine calibration, the data alignment system moves the sampler clock signals earlier or later in time relative to the sampled data based on the first bit, a second bit, and a third bit in the sampled data.