LVDS Driving Circuit With Transition Acceleration for Fast Slew Rates
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Solution Overview
Problem
Low voltage differential signal (LVDS) driving circuits for high-speed transmission interfaces, such as HDMI and USB, face inefficiencies due to slow signal slew rates caused by limited operation voltage, affecting transmission efficiency.
Innovation Solution
The implementation of a low voltage differential signal driving circuit with a transition accelerator that couples differential output terminals to high and low voltage sources based on control signals, accelerating signal transitions and maintaining proper speed without being affected by low operation voltage, utilizing an automatic level selector and output level detector to generate reference voltages and control signals for optimal transition acceleration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If low operation voltage is used to save power consumption, then power consumption is reduced, but signal slew rate becomes slow and transmission efficiency is affected
Solution Approach 1:
The circuit dynamically switches between low voltage mode (for power saving) and high voltage mode (for fast signal transition) based on the operational state. The transition accelerator circuit is enabled only during signal transitions to boost slew rate, while remaining inactive during steady states to maintain low power consumption.
Solution Approach 2:
The patent changes the voltage parameter dynamically by introducing a transition accelerator that temporarily raises the operating voltage during signal transitions. This allows the system to achieve high slew rates when needed while maintaining low operating voltage for power savings during normal operation.
2Speed
If transition accelerator is added to speed up signal transitions, then signal slew rate is improved, but device complexity increases
Solution Approach 1:
The transition accelerator acts as an intermediary circuit between the LVDS driving circuit and the transmission interface. It mediates the voltage levels by providing temporary high voltage boosts during transitions without requiring complete redesign of the core LVDS circuitry, thus limiting the increase in device complexity.
Solution Approach 2:
The patent segments the voltage boosting function into a separate transition accelerator module that can be independently controlled. This segmentation allows the core LVDS circuit to remain simple while the acceleration function is added as a modular component with dedicated control logic.
3Productivity
If high voltage source is coupled to speed up transitions, then transmission efficiency is improved, but power consumption increases
Solution Approach 1:
The high voltage source is activated periodically only during signal transitions rather than continuously. The control circuit detects transition events and triggers the transition accelerator only at these moments, achieving high transmission efficiency during transitions while maintaining low power consumption during steady states.
Solution Approach 2:
The transition accelerator prepares and charges the high voltage source in advance during steady states, so that when a transition is needed, the high voltage is already ready to be applied immediately. This preliminary charging allows fast transitions without requiring continuous high voltage application, thus reducing overall power consumption.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This solution effectively speeds up signal transitions in LVDS driving circuits, ensuring efficient transmission even at low operation voltages, by directly acting on the impedance element to reduce the RC charging time constant and adapt transition duration to specific transmission interfaces, thus meeting performance requirements.
Implementation Method 1
directly acting on the impedance element to reduce the RC charging time constant
Implementation Method 2
The automatic level selector outputs a reference voltage corresponding to the transmission interface
Implementation Method 3
The output level detector generates a low-high transition acceleration control signal based on the data signal, the reference voltage, and a VTXP signal at the positive differential output terminal
Data Source
AI summary
A low voltage differential signal driving circuit including positive and negative differential output terminals, an automatic level selector, an output level detector and a transition accelerator. The positive and negative differential output terminals provide a transmission interface with a differential output signal for transmission of a data signal. The automatic level selector outputs a reference voltage corresponding to the transmission interface. The output level detector generates a low-high (or high-low) transition acceleration control signal based on the data signal, the reference voltage, and VTXP signal at the positive differential output terminal (or VTXN signal at the negative differential output terminal). In accordance with the low-high (or high-low) transition acceleration control signal, the transition accelerator couples the positive (or negative) differential output terminal to a high voltage source and couples the negative (or positive) differential output terminal to a low voltage source to accelerate transition of the differential output signal.