CMOS Quarter-Rate Multiplexer Circuit Design for High-Speed Serial Links
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Solution Overview
Problem
Conventional multiplexers face challenges in achieving high-speed clock generation and distribution due to increased power consumption as operational speeds increase, making it difficult to support higher data transfer rates in modern applications like cloud computing and carrier networks.
Innovation Solution
A CMOS multiplexer circuit design with a first and second stage data path multiplexer circuit, utilizing unequally sized transmission gates and additional inverters and transmission gates to improve bandwidth and balance jitter, while reducing power consumption by absorbing input data retiming into a previous multiplexing stage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If conventional multiplexer designs are used to increase operational speed, then bandwidth improves, but power consumption increases
Solution Approach 1:
The multiplexer is divided into two stages: a first stage that selects between multiple input data signals (e.g., 4:1 multiplexing) and a second stage that selects between the outputs of the first stage. This segmentation allows each stage to operate at lower speeds while achieving higher overall bandwidth, thereby reducing power consumption compared to a single-stage high-speed design
Solution Approach 2:
The first stage multiplexer performs preliminary selection of data signals before the second stage. By pre-processing and reducing the number of signals early in the pipeline, the second stage operates on fewer signals at lower speed, optimizing the overall power-speed tradeoff
2Productivity
If conventional multiplexer designs are used to support higher data transfer rates, then bandwidth improves, but clock distribution difficulty increases
Solution Approach 1:
The clock distribution is segmented to match the two-stage architecture, with the first clock signal controlling the first stage multiplexer and the second clock signal controlling the second stage multiplexer. This allows independent optimization of clocking for each stage, simplifying overall clock distribution while supporting high data transfer rates
Solution Approach 2:
The multiplexer uses dynamic clocking where the first and second clock signals can have different frequencies and phases. The first stage may operate at a lower clock frequency while the second stage operates at a higher frequency, allowing adaptive speed optimization without complex unified clock distribution
Data Source
AI summary
Various aspects provide for a multiplexer for high-speed serial links. For example, a system can include a first stage data path multiplexer circuit and a second stage data path multiplexer circuit. The first stage data path multiplexer circuit comprises a first inverter circuit to select a first data signal from a set of data signals and a second inverter circuit to select a second data signal from the set of data signals. The first inverter circuit comprises a first set of inverters and a first set of transmission gates. The second inverter circuit comprises a second set of inverters and a second set of transmission gates. The second stage data path multiplexer circuit is configured as a third inverter circuit to select the first data signal or the second data signal as an output data signal. The third inverter circuit comprises a third set of inverters and a third set of transmission gates.