Phase Rotator Circuit Using TIA Conversion for High-Speed Links
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Solution Overview
Problem
Current-mode logic (CML) based phase rotators face efficiency and bandwidth limitations at higher speeds, leading to increased power demands and reduced performance in high-frequency clock data recovery systems.
Innovation Solution
A phase rotator system incorporating a phase interpolation stage with gain stages and a transimpedance amplifier (TIA) stage, using current-source loads instead of resistors, and employing current-output digital-to-analog converters to provide weight signals, allowing for finer control of phase rotation and bandwidth with reduced power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If CML-based phase rotators are used to achieve phase rotation functionality, then the structure remains simple, but power consumption increases and efficiency decreases at high frequencies
Solution Approach 1:
The patent changes the operating parameters by using voltage-mode logic instead of current-mode logic, and employs transimpedance amplifiers to convert current signals to voltage signals. This parameter change allows the system to achieve the same phase rotation function with lower power consumption at high frequencies, directly resolving the contradiction between structural simplicity and power efficiency.
2Productivity
If CML-based phase rotators operate at higher speeds to increase data rates, then productivity increases, but power demands increase and efficiency decreases
Solution Approach 1:
The patent substitutes the current-mode logic mechanism with a voltage-mode logic mechanism combined with transimpedance amplification. This substitution enables the system to operate at higher data rates with reduced power demand, as the voltage-mode approach with TIA conversion is more energy-efficient at high speeds compared to traditional CML architectures.
3Ease of operation
If weighting currents are applied to achieve phase shifting in CML architecture, then phase rotation is achieved, but the differential output current requires load resistors to convert to voltage, increasing complexity
Solution Approach 1:
The patent introduces transimpedance amplifiers as intermediary devices that convert the differential current output from the phase shifter into a differential voltage output. This intermediary conversion stage simplifies the overall architecture by eliminating the need for separate load resistors and subsequent voltage conversion stages, thereby reducing complexity while maintaining ease of phase shifting operation.
Data Source
AI summary
A phase rotator apparatus has phase interpolation and transimpedance amplifier (TIA) stages. This separates gain and bandwidth as degrees of design freedom, facilitating a reduction in power consumption while enabling the data link to transmit and receive higher speed data. Four phases of an incoming signal are combined by the phase interpolation stage using weighting currents and current-source loads to produce a phase shifted current based signal that the TIA stage receives as input. The TIA stage then converts the signal to a voltage based signal. The quiescent operating voltage of the stage outputs can be maintained with common mode feedback circuits and injector currents.