Single-Ended Receiver Reference Tracking for Fast Startup
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Solution Overview
Problem
In single-ended AC-coupled communication receivers, the termination voltage and reference voltage do not remain centered around the input signal until the line reaches its DC balanced point, leading to prolonged startup times and increased receiver jitter due to the tradeoff between startup time and ripple in RC filters.
Innovation Solution
A communication receiver is designed to detect peak high and low pulses and average these peak values to generate a reference voltage for a comparator, using an additional averaging portion that acts as a second RC filter to control the relaxation of the peak detection circuit, thereby reducing ripple and allowing the reference point to track the DC component as it settles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If an RC filter is used to extract the DC component, then the reference voltage is stabilized, but the startup time increases and receiver jitter increases due to the tradeoff between startup time and ripple
Solution Approach 1:
The patent divides the reference voltage generation into two separate circuits: a tracking voltage reference generator that provides fast response with higher ripple, and a filtered voltage reference generator that provides stable reference with lower ripple. The segmented approach allows each circuit to optimize for its specific function rather than trying to achieve both goals in a single RC filter.
Solution Approach 2:
The patent combines the outputs of the tracking voltage reference generator and the filtered voltage reference generator through an averaging circuit. This merging of two reference voltage sources allows the system to benefit from both the fast startup of the tracking generator and the low ripple of the filtered generator, resolving the contradiction between startup time and reference stability.
2Stability of the object's composition
If an RC filter is used to extract the DC component, then the reference voltage is stabilized, but the receiver jitter increases due to ripple
Solution Approach 1:
The patent segments the reference voltage generation into two functional parts: a tracking generator for fast response and a filtered generator for stability. This segmentation allows the system to avoid the high ripple that would otherwise be present in a fast-response single-ended reference circuit, thereby reducing receiver jitter while maintaining stability.
Solution Approach 2:
By merging the tracking voltage reference (fast response) and filtered voltage reference (low ripple) through averaging, the system achieves a combined reference voltage that has both fast startup characteristics and low ripple, thus improving receiver reliability without sacrificing reference stability.
3Measurement precision
If the line does not reach DC balanced point quickly, then the termination voltage and reference voltage are not centered around the input signal, but extending the startup window beyond specification is not acceptable
Solution Approach 1:
The tracking voltage reference generator performs preliminary action by quickly acquiring and tracking the DC component of the input signal during startup. This preliminary tracking provides an initial centered reference voltage before the line fully settles to its DC balanced point, enabling the receiver to operate correctly within the specified startup window.
Solution Approach 2:
The tracking voltage reference generator uses feedback from the differential input signal to continuously adjust and center the reference voltage around the input signal level. This feedback mechanism ensures that the reference voltage remains accurately centered even during the transient startup period before the line reaches its final DC balanced state.
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 solution enables a faster startup time with lower ripple, allowing the receiver to achieve reasonable reference values with fewer input data values and maintain noise margins by damping the ripple in the VREF_TRACK signal.
Implementation Method 1
A typical circuit that extracts the DC component of a switching signal uses an RC filter
Implementation Method 2
The filter also requires a representative density of positive and negative pulses to accurately render an average
Data Source
Figure 1
Figure 2
AI summary
A receiver includes an input node coupled to receive an analog signal, a first switch coupled between the input node and a first node, a second switch coupled between the input node and a second node, a first resistive element coupled between the first node and a reference node, a second resistive element coupled between the second node and the reference node, a first capacitive element coupled to the first node, and a second capacitive element coupled to the second node. The receiver also includes a comparator having a first input coupled to the input node to receive the analog signal, and a second input coupled to the reference node to receive a reference voltage, wherein an output of the comparator controls the first and second switches.