SerDes Pattern Detection for Equalization Freeze and CDR Lock

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Solution Overview

Problem

Existing SerDes receiver systems face challenges in achieving optimal jitter tolerance and equalization adaptation due to limitations in detecting dual tones and low activity periods, leading to sub-optimal performance and potential drifting of the CDR circuit sampling point.

Innovation Solution

A pattern detector is implemented to detect insufficiently randomized pattern periods and low activity periods, generating a freeze signal to disable equalization adaptation during these times, allowing for precise synchronization and delaying freeze de-assertion to help the CDR circuit regain lock to the data eye center.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If equalization adaptation is continuously enabled to maintain optimal jitter tolerance, then equalization performance is improved, but sub-optimal adaptation occurs during insufficiently randomized pattern periods

Engineering Contradiction:

Improvejitter toleranceVSAvoidequalization adaptation accuracy

Core Design Contradiction:

ReliabilityVSManufacturing precision

Solution Approach 1:

The pattern detector proactively identifies insufficiently randomized patterns and low activity periods before they cause harmful adaptation effects. By detecting these conditions in advance and generating freeze signals, the system prevents sub-optimal equalization adaptation from occurring, thereby maintaining both reliability and adaptation accuracy without continuous monitoring during all operating conditions.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent extracts and isolates the harmful adaptation process during specific problematic periods by implementing equalization adaptation freeze. The adaptation is selectively disabled only during detected insufficiently randomized pattern periods and low activity periods, while remaining enabled during normal randomized data conditions. This selective extraction of the adaptation function resolves the contradiction by maintaining adaptation accuracy when needed while preserving reliability during critical periods.

Inventive Principle:

Principle #2Taking out (Extraction)

2Manufacturing precision

If equalization adaptation is enabled during low activity periods to maintain optimal performance, then equalization accuracy is improved, but CDR circuit sampling point drifting occurs

Engineering Contradiction:

Improveequalization adaptation accuracyVSAvoidCDR sampling point stability

Core Design Contradiction:

Manufacturing precisionVSStability of the object's composition

Solution Approach 1:

The pattern detector acts as an intermediary between the data stream and the equalization adaptation process. It monitors the incoming data for low activity conditions and insufficient randomization, and based on this monitoring, controls the timing and enabling of adaptation. This intermediary function allows the system to maintain adaptation accuracy during normal conditions while preventing CDR sampling point drifting during low activity periods by selectively freezing adaptation when needed.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Manufacturing precision

If pattern detection is implemented to protect equalization adaptation, then adaptation accuracy is improved, but dual tone detection capability is insufficient

Engineering Contradiction:

Improveequalization adaptation accuracyVSAvoidpattern detection coverage

Core Design Contradiction:

Manufacturing precisionVSAdaptability or versatility

Solution Approach 1:

The pattern detector is designed with multi-functional capability to detect multiple types of harmful patterns including single tones, dual tones, and low activity periods. By incorporating universal detection mechanisms that can identify various pattern types through analysis of data stream characteristics, the system achieves comprehensive pattern detection coverage while maintaining high adaptation accuracy across different operating conditions and pattern types.

Inventive Principle:

Principle #6Universality (Multi-functionality)

Data Source

PatentUS8548038B2Pattern detector for serializer-deserializer adaptation

Publication Date: 2013.10.01 AVAGO TECHNOLOGIES INTERNATIONAL SALES PTE LTD

AI summary

In described embodiments, a Serializer-Deserializer (SerDes) receiver includes a pattern detector that allows for detection of insufficiently randomized pattern periods and low activity periods. A freeze of equalization adaptation during these periods might occur by embedding disqualifying patterns into adaptation data. Some embodiments also allow for detection of long intervals of freeze, and so delay a freeze de-assertion in order for a clock and data recovery (CDR) circuit of the receiver to regain lock to the serial data. Embedding freeze information in the receive data allows for precise synchronization of receive data and freeze.