Multi-Stage Phase Mixer Circuit for Equal Clock Phase Steps
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Solution Overview
Problem
Conventional phase mixer circuits fail to maintain equal phase differences between output clock signals due to drivability differences between pull-up and pull-down units, resulting in reduced resolution and increased jitter, especially around intermediate weight control code values.
Innovation Solution
A multi-stage phase mixer circuit is implemented, comprising a first-stage mixer for coarse control and a second-stage mixer for fine control, using thermometer codes to ensure consistent phase mixing across the entire range of weight control codes, thereby equalizing phase differences between output clock signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a single-stage phase mixer circuit is used with weight control codes to adjust output phase, then the phase can be adjusted between two input clock signals, but the phase differences between adjacent output clock signals become unequal due to drivability differences between pull-up and pull-down units
Solution Approach 1:
The phase mixer is divided into multiple stages: a first phase mixer that performs coarse phase adjustment and a second phase mixer that performs fine phase adjustment. This segmentation allows each stage to handle specific portions of the phase control range, ensuring equal phase differences across the entire output spectrum while maintaining full phase adjustment capability.
2Measurement precision
If weight control codes are used to increase output clock signal resolution, then more precise phase control is achieved, but jitter increases due to unequal phase differences between adjacent output signals
Solution Approach 1:
By segmenting the phase mixing into coarse and fine stages, each stage operates with optimized control codes that ensure equal phase stepping. The coarse stage handles larger phase increments while the fine stage handles smaller increments, together providing high resolution output with equal phase differences that minimize jitter.
Solution Approach 2:
The invention changes the control parameter structure by using separate coarse and fine control codes instead of a single weight control code. This parameter transformation allows the system to maintain precise resolution while ensuring equal phase differences, thereby reducing jitter in the output clock signal.
3Manufacturing precision
If a multi-stage phase mixer circuit is implemented with coarse and fine control signals, then equal phase differences are achieved across the entire range, but the circuit complexity increases
Solution Approach 1:
The phase mixer is segmented into two functional stages with distinct control signals. The first phase mixer handles coarse adjustment and the second handles fine adjustment. This segmentation achieves equal phase differences across the full range while organizing the complexity into manageable, functionally-distinct modules that can be independently optimized.
Data Source
AI summary
A multi-stage phase mixer circuit includes: a first phase mixer configured to receive first and second input clock signals and output a first intermediate clock signal according to control of a first coarse control signal; a second phase mixer configured to receive the first and second input clock signals and output a second intermediate clock signal according to control of a second coarse control signal; and a third phase mixer configured to receive the first and second intermediate clock signals and output an output clock signal according to control of a fine control signal.