Segmented SST Transmitter Slices for Orthogonal Zcal and FFE
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Solution Overview
Problem
Existing segmented multiple level source-series terminated (SST) transmitters face limitations in implementing impedance tuning (Zcal) and feed forward equalization (FFE) operations, with Zcal operations often constrained by FFE units or vice versa, necessitating new techniques for independent and orthogonal implementation.
Innovation Solution
The system performs impedance tuning within each output driver slice of a segmented SST transmitter, using fine and coarse tuning methods, and assigns driver slices to specific FFE taps for orthogonal FFE resolution, with binary-weighted devices and digital control, enabling separate and independent impedance tuning and FFE operations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If Zcal and FFE are implemented together using conventional arrangements, then the transmitter can perform both impedance tuning and equalization, but the Zcal operations are limited by the FFE unit and FFE operations are limited by the Zcal operations
Solution Approach 1:
The output driver is divided into multiple parallel-connected driver slices, where each slice can be independently configured for either Zcal or FFE operations. This segmentation allows the transmitter to perform impedance tuning and equalization independently by selectively enabling specific slices for each function, thereby resolving the mutual limitation problem while maintaining operational independence.
Solution Approach 2:
The driver slices are designed with multi-functionality, capable of serving either Zcal or FFE purposes. By configuring different slices for different functions, the system achieves universal operation where the same hardware resources can adapt to different operational modes without requiring separate dedicated circuits for each function.
2Measurement precision
If multiple driver slices are used for FFE, then FFE resolution can be improved, but the number of enabled slices must be changed which affects impedance matching
Solution Approach 1:
The driver is segmented into multiple parallel slices that can be independently controlled. For FFE operations, specific slices can be enabled to achieve the desired resolution without affecting the overall number of active slices for impedance matching, as each slice contributes additively to the FFE function while maintaining the total drive strength.
Solution Approach 2:
Different driver slices can be configured with different local characteristics (e.g., different weights or tap positions) to optimize FFE resolution. The local quality of each slice can be adjusted independently through selective enabling and weighting, allowing high FFE resolution while maintaining global impedance matching through proper configuration of the enabled slices.
3Manufacturing precision
If conventional Zcal arrangements are used, then impedance tuning can be performed, but the tuning range and precision are limited
Solution Approach 1:
The impedance tuning function is distributed across multiple parallel driver slices, each capable of contributing to the overall impedance adjustment. By selectively enabling and configuring different slices, the system achieves both fine precision (through individual slice control) and wide tuning range (through combinatorial configuration of multiple slices).
Solution Approach 2:
The impedance tuning capability is made dynamic through selective enabling of different driver slice combinations. The system can adaptively adjust the number and configuration of active slices based on the desired impedance target, providing both precision and wide range tuning capabilities that are not available in conventional static Zcal arrangements.
Data Source
AI summary
Embodiments of the present disclosure provide systems and methods for implementing separate and orthogonal impedance tuning (Zcal) and feed forward equalization (FFE) operations of a segmented multiple level source-series terminated (SST) transmitter. An SST transmitter output driver comprising a plurality of parallel-connected output driver slices coupled to a data communication link and a multiple-tap FFE unit comprising at least one pre-cursor tap, main tap or post-cursor tap. The system performs impedance tuning within each of the plurality of parallel-connected output driver slices of the output driver. The system performs FFE resolution on the plurality of parallel-connected output driver slices of the output driver by assigning respective ones of the plurality of parallel-connected output driver slices to a specific FFE tap of the of the at least one pre-cursor tap, main tap or post-cursor tap of the FFE unit.