I2C Isolated Bidirectional Communication Circuit
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Solution Overview
Problem
Existing I2C bidirectional communication systems face challenges in detecting acknowledge (ACK) signals and maintaining signal direction across isolation barriers, leading to potential bus lockup conditions due to noise margin reduction and part-to-part variation in voltage levels.
Innovation Solution
The system employs a current source internal to the communication interface device to pull I2C buses to logic high levels and includes a detector to sense when a remote device pulls the signal to logic low, using a current comparator and controlled current sources to monitor signals and prevent bus lockup, while maintaining fast switching speeds.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the signal is driven just above the specification levels, then power consumption is reduced, but noise margin is reduced and reliability deteriorates
Solution Approach 1:
The patent changes the voltage level parameter by introducing a boosted voltage level (VBOOST) that is higher than the standard logic high level. This allows the signal to be driven with sufficient noise margin while maintaining power efficiency through controlled switching between voltage levels. The voltage booster circuit dynamically adjusts the output voltage based on the input signal state, providing enhanced noise immunity without continuous high power consumption.
2Reliability
If isolation barriers are introduced between I2C devices, then electrical isolation is achieved, but signal direction detection becomes difficult
Solution Approach 1:
The patent introduces a voltage booster circuit as an intermediary component between the isolated I2C devices. This intermediary actively senses the signal transitions and amplifies them to maintain proper logic levels across the isolation barrier. The voltage booster includes control logic that detects the direction of signal transitions and appropriately boosts the voltage to indicate the correct signal direction to the receiving device, thereby solving the direction detection problem while maintaining isolation.
3Reliability
If current sources are used to pull I2C buses to logic high, then signal levels are maintained, but bus lockup conditions may occur due to competing pull-down forces
Solution Approach 1:
The patent implements dynamic control of the current sources based on the detected signal state and transition direction. The voltage booster circuit continuously monitors the I2C bus signals and dynamically adjusts the current source output accordingly. When an ACK condition is detected or when signal transitions indicate a need for higher drive strength, the current source is activated or enhanced to pull the bus to logic high more strongly, preventing lockup conditions while maintaining signal level stability during normal operation.
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 detects ACK signals and maintains data direction across isolation barriers, preventing bus lockup conditions and ensuring reliable communication by using a current comparator and controlled current sources to manage signal levels.
Implementation Method 1
The system employs a current source internal to the communication interface device to pull I2C buses to logic high levels and includes a detector to sense when a remote device pulls the signal to logic low, using a current comparator and controlled current sources to monitor signals
Data Source
AI summary
This disclosure describes a circuit implementation providing the functions necessary to implement an isolated I 2 C bidirectional port. The technique implements a current source as a pull up device on at least one side of the isolation system. The circuit manages and communicates bidirectional data across an isolation barrier. A method of communicating bidirectional signals and an I 2 C acknowledge (ACK) or clock stretching through an isolation channel is disclosed.