Digital Isolator Sleep-Wake Circuit for High CMTI
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Solution Overview
Problem
Digital isolators in noisy industrial environments face challenges in achieving high Common Mode Transient Immunity (CMTI) and low power consumption while maintaining reliable communication across isolation barriers.
Innovation Solution
A digital isolator system comprising a transmitter that generates buffered differential signals, an isolation barrier, and a receiver that converts these signals into valid logic levels with inherited propagation delays, along with a control method that enables power-saving features by disabling components during idle periods and using a validation circuit to detect signal patterns for resetting and timing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the digital isolator uses continuous signal transmission to ensure reliable communication, then the communication reliability is improved, but the power consumption increases
Solution Approach 1:
The isolator enters sleep mode during idle periods and wakes up periodically to check for incoming signals. The receiver circuit is disabled during sleep mode and only activated when a wake-up event occurs, such as detecting a signal edge or receiving a wake-up command. This periodic activation significantly reduces average power consumption while maintaining communication reliability when needed.
Solution Approach 2:
The isolator dynamically adjusts its operational state between active and sleep modes based on communication activity. The system transitions from a static continuous operation mode to a dynamic state-changing mode, where power consumption is adjusted according to actual communication needs, thereby resolving the contradiction between reliability and power consumption.
2Reliability
If the digital isolator activates all components continuously to maintain high CMTI performance, then the Common Mode Transient Immunity is improved, but the power consumption increases
Solution Approach 1:
The high-CMTI circuitry is activated only during periods when communication is required or when transient immunity is actually needed (such as during wake-up transitions). During steady-state sleep mode, the system maintains the capability to achieve high CMTI when activated, but does not consume the power required to maintain continuous high-CMTI performance, thus resolving the contradiction.
3Use of energy by moving object
If the isolator enters sleep mode to reduce power consumption, then the power consumption is reduced, but the response time to resume communication increases
Solution Approach 1:
The isolator performs preliminary actions during the wake-up process by detecting signal edges or wake-up commands that trigger immediate activation. The system prepares to wake up by monitoring for these trigger conditions even in sleep mode, and once triggered, the activation process is expedited, minimizing the actual wake-up time while still allowing deep sleep mode for power savings.
Data Source
AI summary
An isolator system has a transmitter configured to generate a first pair of buffered differential signals base based on an input signal; an isolation barrier having an input side coupled to the transmitter to receive the first pair of buffered differential signals, and an output side configured to provide a second pair of differential signals; and a receiver coupled to the output side of isolation barrier to receive the second pair of differential signals, wherein the receiver provides an output signal based on restoring the second pair of differential signals into a third pair of differential signals, wherein the output signal is converted from the third pair of differential signals and is a duplicate of the input signal with inherited propagation delays.