Output Driver Impedance Control for High-Speed Data Transmission
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Solution Overview
Problem
In high-speed electronic systems, data signals with small amplitudes can be distorted due to mismatched output impedance of data transmission circuits and transmission lines, leading to abnormal waveforms and reduced data transmission speed, and on-die termination (ODT) circuits require impedance calibration to address this issue.
Innovation Solution
A data transmission circuit comprising a control signal generator and an output driver, where the control signal generator produces count signals in response to a clock signal, and a signal converter generates pull-up and pull-down control signals to drive the transmission data signal, enhancing impedance matching and drivability during impedance calibration tests.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If data signals are transmitted with small amplitudes to improve data speed, then data transmission speed is improved, but signal waveform distortion occurs due to impedance mismatch
Solution Approach 1:
The patent dynamically adjusts the output impedance of the data transmission circuit by changing the resistance value of the ODT resistor based on detected signal waveform characteristics (overshoot/undershoot levels). This parameter change allows the circuit to maintain impedance matching under different operating conditions, preventing waveform distortion while enabling high-speed small-amplitude signal transmission
Solution Approach 2:
The patent implements a feedback mechanism where the data transmission circuit detects the waveform characteristics of transmitted signals and uses this information to automatically adjust the ODT resistor value. The detection unit monitors signal quality and feeds this information back to the control unit, which then modifies the termination impedance to eliminate overshoot and undershoot, ensuring reliable high-speed transmission
2Reliability
If ODT circuits are used for impedance matching, then signal waveform integrity is improved, but impedance varies according to PVT conditions requiring calibration
Solution Approach 1:
The patent enables the ODT circuit to perform self-calibration by automatically detecting its own impedance matching status through waveform analysis and adjusting the ODT resistor value accordingly. The calibration process is executed autonomously within the data transmission circuit itself, eliminating the need for external calibration equipment or complex test setups while maintaining accurate impedance matching across PVT variations
3Use of energy by moving object
If switching circuits are added to ODT circuits to reduce power consumption, then power consumption is reduced, but impedance control complexity increases
Solution Approach 1:
The patent employs dynamic control of the ODT resistor value based on real-time signal waveform conditions rather than static fixed impedance. The switching circuit selectively activates different ODT resistor values (e.g., 24.5Ω, 49Ω, 98Ω) depending on the detected overshoot/undershoot characteristics, allowing the circuit to maintain optimal impedance matching only when needed while reducing power consumption during normal operation
Data Source
AI summary
Data transmission circuits are provided. The data transmission circuit includes a control signal generator and an output driver. The control signal generator generates a pull-up control signal and a pull-down control signal by using a count signal that changes in response to a clock signal during a drive control period. The output driver receives an internal data signal and drives a transmission data signal in response to the pull-up control signal and the pull-down control signal.