SerDes Transmitter Dual DCC Loops for Duty Cycle Distortion
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Solution Overview
Problem
High-speed serializer/deserializer (SerDes) systems face duty cycle distortion issues due to non-ideal duty cycles and unbalanced rise/fall times in transmitter clock signals, leading to data distortion, especially at high data rates like 50 Gbps, where conventional correction methods are inefficient and power-intensive.
Innovation Solution
A dual duty cycle correction loop system is implemented, comprising a main path and a replica path with multiplexers and drivers, using pre-defined data patterns to correct duty cycle distortions during chip initialization and dynamic adjustments to address process variations and temperature/voltage drift, minimizing power consumption and size.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional duty cycle correction methods are used in high-speed SerDes systems, then duty cycle distortion can be corrected, but power consumption increases and efficiency decreases
Solution Approach 1:
The correction system is divided into two independent loops: a main DCC loop that operates continuously and a calibration DCC loop that operates periodically. This segmentation allows the main loop to use minimal power for ongoing corrections while the calibration loop periodically optimizes accuracy, reducing overall power consumption compared to continuous high-precision correction.
Solution Approach 2:
The calibration DCC loop operates periodically rather than continuously, performing duty cycle calibration at intervals determined by control logic. This periodic operation significantly reduces power consumption compared to continuous calibration methods, while still maintaining correction accuracy through regular optimization cycles.
2Device complexity
If a single duty cycle correction loop is used, then the system is simpler, but it cannot effectively correct both initial duty cycle distortions and dynamic variations
Solution Approach 1:
The correction functionality is segmented into two specialized loops: the main DCC loop handles continuous duty cycle correction during normal operation, while the calibration DCC loop performs periodic accuracy optimization. This segmentation enables each loop to be optimized for its specific function, improving overall correction effectiveness without excessive complexity.
Solution Approach 2:
A control logic unit acts as an intermediary between the main DCC loop and calibration DCC loop, managing their coordinated operation. The control logic determines when calibration is needed and switches between loops appropriately, enabling the system to achieve high correction effectiveness through structured multi-loop architecture without requiring complex direct coupling between correction mechanisms.
3Measurement precision
If duty cycle correction is implemented continuously, then accuracy is maintained, but power consumption and processing overhead increase
Solution Approach 1:
The calibration DCC loop operates periodically under control of control logic that determines when calibration is necessary based on system state. This periodic calibration approach maintains duty cycle accuracy through regular optimization while consuming significantly less power than continuous calibration methods.
Solution Approach 2:
The system segments correction operations into continuous low-power main loop corrections and periodic high-precision calibration loop corrections. This segmentation allows the system to maintain acceptable accuracy through continuous operation while using periodic calibration only when needed, optimizing the balance between accuracy and power consumption.
Data Source
AI summary
Aspects of the invention include receiving, by a controller, an indication of a chip initialization for a duty cycle correction (DCC) circuit, wherein the duty cycle correction circuit includes a main path including a main multiplexer (MUX) having a first input and a main driver circuit, a replica path including a replica MUX having a second input and a replica driver circuit, a selection MUX connected to the main path and the replica path, operating the selection MUX, during a period for the chip initialization, to select the main path as an input to the selection MUX, inputting a pre-defined data pattern to the main path, comparing an output of the selection MUX with the pre-defined data pattern to determine duty cycle issue, and generating an adjustment vector based on the determined duty cycle issue.