SerDes PVT Detection via Closed-Loop DFE Monitoring
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Solution Overview
Problem
Serializer/deserializer (SerDes) devices face performance variations due to process, voltage, and temperature (PVT) variations, leading to significant data path gain variations, which result in sub-optimal bit error rate (BER) performance and inefficient power consumption, as existing open-loop compensation methods are optimized for worst-case scenarios.
Innovation Solution
A closed-loop compensation method is implemented in the SerDes receiver, which detects PVT conditions by monitoring the decision feedback equalizer (DFE) target level and variable gain amplifier (VGA) gain, adjusting the VGA and LEQ/DFE data path gains to maintain optimal data path gain and attenuation, using a voltage regulator and differential pair gain adjustments.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If open-loop PVT compensation circuits are used to compensate for process, voltage and temperature variations, then device performance can be maintained across PVT corners, but the device dissipates more power and consumes more area than required for typical applications
Solution Approach 1:
The patent measures the actual data path gain at power-up using the DFE H0 target level before normal operation begins. This preliminary measurement allows the system to establish an accurate baseline of the actual gain condition, enabling subsequent closed-loop compensation to operate efficiently without requiring excessive power budgeted for worst-case scenarios
Solution Approach 2:
The patent implements closed-loop compensation by continuously monitoring the DFE H0 target level and using this feedback to dynamically adjust the VGA gain setting. This feedback mechanism allows the system to adapt to actual PVT conditions rather than relying on open-loop pre-compensation, reducing power consumption while maintaining performance consistency across PVT corners
2Reliability
If the SerDes device is designed for the worst case scenario to ensure performance across all PVT corners, then reliability is improved, but power consumption and area increase beyond what is required for typical applications
Solution Approach 1:
The system performs a preliminary measurement of the actual data path gain at power-up using DFE H0 target level monitoring. This allows the device to determine the actual PVT corner conditions rather than assuming worst-case scenarios, enabling efficient resource allocation without requiring excessive area for over-engineering
Solution Approach 2:
The patent employs dynamic adjustment of VGA gain based on real-time monitoring of DFE H0 target level. This dynamic approach allows the system to adapt to actual operating conditions, eliminating the need for static worst-case design margins that would consume additional area
3Reliability
If VGA gain is increased to compensate for low gain corner (fast process, low VDD, high T), then BER performance is improved, but the signal becomes highly compressed and loses adaptation information in high gain corner
Solution Approach 1:
The patent uses closed-loop feedback by monitoring the DFE H0 target level to dynamically adjust VGA gain. This feedback mechanism prevents over-compensation in high gain corners by continuously checking whether the actual gain condition requires additional amplification, thereby preserving signal adaptation information while ensuring adequate BER performance in low gain corners
Data Source
AI summary
In described embodiments, process, voltage, temperature (PVT) compensation in a serializer/deserializer (SerDes) device employs a closed loop adaptation compensation that is incorporated into the SerDes receiver adaptation process. A detection method, where the adapted decision feedback equalizer (DFE) target level (e.g., tap H0) is monitored, employs this DFE target level when implementing a closed loop variable gain amplifier adaptation. The DFE target level in conjunction with the VGA level is used to control the PVT setting to maintain target SerDes data path gain by detecting aPVT corner condition. The detected PVT corner condition is employed to generate a control signal to further adjust the LEQ and DFE data path differential pair gain as required by the PVT condition.