Two-Wire Bus Interface With Adjustable Bias Resistors
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Solution Overview
Problem
Two-wire bus systems face issues with undefined input levels when not in use, leading to reflections, which existing termination resistors fail to adequately address, necessitating additional pull-up and pull-down resistors to prevent such conditions.
Innovation Solution
A bus interface with adjustable pull-up and pull-down resistor devices, implemented using digital potentiometers and switches, allows for dynamic resistance value setting based on control signals to manage voltage levels and prevent undefined inputs, featuring a computing unit to evaluate voltages and activate current paths accordingly.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If termination resistors are arranged at the ends of the bus line to avoid reflections, then reflections are reduced, but the voltage is pulled to zero which creates undefined input levels for bus subscribers
Solution Approach 1:
The patent applies local quality by implementing different resistor configurations at different locations on the bus. Termination resistors are placed at bus ends to handle reflections, while additional pull-up and pull-down resistors are strategically positioned at specific locations to maintain valid voltage levels. This localized differentiation allows each resistor to serve its specific function without interfering with others, resolving the contradiction between reflection reduction and preventing undefined input levels.
2Reliability
If additional pull-up and pull-down resistors are provided to prevent undefined input levels, then reliability is improved, but device complexity increases
Solution Approach 1:
The patent employs dynamics by making the resistor connections controllable and switchable rather than fixed. Switches are introduced to dynamically connect or disconnect pull-up and pull-down resistors based on bus activity states. During active communication, termination resistors are connected while pull-up/pull-down resistors are disconnected. During idle periods, the configuration switches to prevent undefined levels. This dynamic reconfiguration reduces overall device complexity by activating only the necessary resistors at any given time.
3Ease of manufacture
If fixed resistance values are used for pull-up and pull-down resistors, then ease of manufacture is improved, but adaptability to different bus conditions is reduced
Solution Approach 1:
The patent applies parameter changes by providing multiple resistor devices with different resistance values (e.g., first pull-up resistor with value R1 and second pull-up resistor with value R2). These different resistance parameters allow the system to adapt to various bus conditions, cable lengths, and loading scenarios. The controller can select appropriate resistance values by switching between different resistor devices, maintaining ease of manufacture with standard resistor components while achieving adaptability through selective configuration.
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
The solution effectively prevents undefined voltage levels during bus inactivity by dynamically adjusting resistance values, ensuring reliable communication and preventing reflections in two-wire bus systems.
Implementation Method 1
The pull-up resistor device is arranged to set a pull-up resistance value based on a pull-up control signal
Implementation Method 2
the pull-down resistor device is arranged to set a pull-down resistance value based on a pull-down control signal
Implementation Method 3
The pull-up resistor device can be designed as a digital potentiometer. Likewise, the pull-down resistor device can be designed as a digital potentiometer
Data Source
AI summary
Bus interface for a two-wire bus with adjustable pull-up/pull-down resistance values. A device has a bus interface for a two-wire bus comprising a first terminal and a second terminal for connection to the two-wire bus, a pull-up resistor device connected to the first terminal for a first conductor of the two-wire bus, and a pull-down resistor device connected to the second terminal for a second conductor of the two-wire bus. The pull-up resistor device is arranged to set a pull-up resistance value based on a pull-up control signal. The pull-down resistor device is arranged to set a pull-down resistance value based on a pull-down control signal.