LVDS Input Circuit for Single-Pair Bidirectional Signaling
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
LVDS signaling requires double the number of connections between sending and receiving circuits, limiting simultaneous bidirectional communication and increasing interconnect complexity, while also facing challenges with reduced noise margins due to parallel termination resistors.
Innovation Solution
Designing LVDS drivers and receivers to enable simultaneous communication over a single pair of signal paths using series resistors and specialized input circuits, including inverters, differential receivers, window comparators, and multiplexers, to maintain appropriate signaling voltages and noise margins.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional LVDS signaling is used with separate signal paths for bidirectional communication, then communication reliability is improved, but the number of connections doubles and device complexity increases
Solution Approach 1:
The patent combines bidirectional communication functionality into a single LVDS signal path by merging the transmitter and receiver operations. The input circuit selectively couples the LVDS signal path to either the driver output or the destination input based on communication direction, eliminating the need for separate signal paths while maintaining full-duplex communication capability.
Solution Approach 2:
The LVDS signal path is designed to serve multiple functions - it can transmit signals from driver to destination and vice versa. The input circuit acts as a universal interface that can receive signals in either direction, allowing the same physical connection to handle both transmit and receive operations simultaneously or alternately.
2Stability of the object's composition
If parallel termination resistors are used in LVDS signaling, then signal stability is improved, but noise margins are reduced
Solution Approach 1:
The patent applies different termination strategies to different parts of the circuit based on local requirements. Series resistors are placed at the driver output to control signal integrity and impedance matching, while the destination input uses parallel termination resistors for stability. This localized approach allows each component to be optimized for its specific function without compromising overall noise margins.
Solution Approach 2:
The input circuit serves as an intermediary between the LVDS signal path and the destination input, providing buffer and level-shifting functionality. This intermediary stage isolates the destination from direct exposure to noisy differential signals while maintaining signal stability through controlled impedance and proper termination at critical points.
3Reliability
If series resistors are added to LVDS signal paths, then signal integrity is improved, but circuit complexity increases
Solution Approach 1:
The patent extracts the impedance matching and signal conditioning functions from the main LVDS receiver circuit and places them in separate series resistor elements at the driver output. This separation allows the core receiver circuit to remain simple while the series resistors handle the complex signal integrity requirements independently.
Data Source
AI summary
First and second devices may simultaneously communicate bidirectionally with each other using only a single pair of LVDS signal paths. Each device includes an input circuit and a differential output driver connected to the single pair of LVDS signal paths. An input to the input circuit is also connected to the input of the driver. The input circuit may also receive an offset voltage. In response to its inputs, the input circuit in each device can use comparators, gates and a multiplexer to determine the logic state being transmitted over the pair of LVDS signal paths from the other device. This advantageously reduces the number of required interconnects between the first and second devices by one half.