Charge-Coupled DFE Receiver for Low-Latency Equalization
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Solution Overview
Problem
Receiver equalization techniques, particularly decision feedback equalization (DFE), face challenges with loop latency and the need for increased sense-amplifiers, leading to power dissipation and silicon area costs, and are prone to latency issues that require loop unrolling, which complicates the integration of feedback within the unit interval.
Innovation Solution
The implementation leverages capacitive switches and a cascade of flip-flop latches to integrate feedback within one unit interval, reducing the need for additional sense-amplifiers and maintaining constant net capacitance, allowing for consistent voltage resolution and single-cycle operation in high-speed serial communications.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If decision feedback equalization (DFE) is implemented to mitigate inter-symbol interference, then equalization performance is improved, but loop latency increases and requires additional sense-amplifiers leading to increased power dissipation and silicon area
Solution Approach 1:
The patent combines the feedback path with the main signal path by directly coupling the DAC output to the S/H common node, merging multiple functions into a single integrated structure that eliminates the need for separate sense-amplifiers while maintaining DFE functionality
Solution Approach 2:
The sample and hold circuit's common node serves multiple functions: it acts as the signal path node, the feedback injection point, and the DAC output node, allowing a single component to perform what traditionally required multiple specialized components
2Loss of time
If loop unrolling is used to integrate feedback within the unit interval, then latency is reduced, but device complexity and integration difficulty increase
Solution Approach 1:
The feedback signal is prepared in advance during the sample phase when the DAC output tracks the S/H output, so that when the hold phase begins and the S/H output goes high-impedance, the feedback is already ready to be coupled without requiring complex timing control or additional latency
3Speed
If additional sense-amplifiers are added to reduce latency, then speed is improved, but power dissipation increases
Solution Approach 1:
The patent extracts and eliminates the unnecessary sense-amplifier components from the traditional DFE architecture, retaining only the essential feedback functionality through direct capacitive coupling, thereby reducing power consumption while maintaining speed
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach reduces the number of required sense-amplifiers, minimizes power dissipation, and maintains consistent voltage resolution, effectively addressing latency and efficiency issues in receiver equalization while enabling high-speed serial communication.
Implementation Method 1
charge is capacitively coupled to or from the first common node during an immediately subsequent hold phase so that the capacitively coupled charge modulates the analog output voltage
Data Source
AI summary
A mixed signal receiver includes a first sample and hold (S/H) circuit having a first S/H input terminal to receive an analog input signal and a first S/H output terminal directly coupled to a first common node; a first data slicer having a first slicer input terminal coupled to the first common node; and a first data-driven charge coupling digital-to-analog converter (DAC) including: (i) a DAC input terminal to receive a first digital signal from a first digital output of the first data slicer, (ii) a DAC output terminal directly coupled to the first common node, (iii) a plurality of capacitor modules configured to be pre-charged during a sample phase, and (iv) logic components, wherein when the logic components toggle a voltage on the plurality of capacitor modules, charge is capacitively coupled to or from the first common node during an immediately subsequent hold phase.