Bi-Directional Buffer Bias Control for Fast I2C Transients
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Solution Overview
Problem
Bi-directional buffers in I2C and PMBUS systems often experience oscillations during signal transitions due to large bias voltages, which can lead to protocol non-compliance and false triggers, especially when connected in series.
Innovation Solution
A bi-directional buffer design incorporating a first and second driving switch, a switch, a comparator, and two operational amplifiers to regulate the voltage difference between input and output signals, with a smaller second bias voltage to minimize oscillations and improve transient response.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a big bias voltage is used between output and input signals, then oscillation is avoided, but the buffer cannot satisfy protocol standards of some bus systems
Solution Approach 1:
The patent implements dynamic bias voltage control by using two operational amplifiers that adjust the bias voltage between output and input signals based on signal transition states. During transient periods, a smaller bias voltage is applied to enable fast response and protocol compliance, while during stable states, a larger bias voltage prevents oscillation. This dynamic adjustment resolves the contradiction between oscillation avoidance and protocol compliance.
Solution Approach 2:
The patent changes the bias voltage parameter from a fixed large value to a variable value that transitions between small and large states. The first operational amplifier generates a first gate signal to control a first driving switch with a first bias voltage, while the second operational amplifier generates a second gate signal to control a second driving switch with a second bias voltage that is smaller than the first. This parameter change enables the system to meet protocol standards during transitions while maintaining oscillation avoidance during steady states.
2Reliability
If a big bias voltage is used between output and input signals, then oscillation is avoided, but transient response becomes slow
Solution Approach 1:
The patent dynamically switches between small and large bias voltages based on the transient state of the signal. During transient transitions, the control circuit applies a smaller bias voltage to enable fast response speed, and during stable operation, it applies a larger bias voltage to prevent oscillation. This dynamic approach resolves the contradiction between fast transient response and oscillation avoidance.
Solution Approach 2:
The patent employs periodic control action where the operational amplifiers continuously monitor the signal transition state and adjust the bias voltage accordingly. The first comparator detects when the input signal reaches a first voltage threshold to turn off the first switch, and a second comparator detects when the input signal reaches a second voltage threshold to turn on the first switch. This periodic monitoring and adjustment enables fast transient response while maintaining oscillation avoidance.
3Adaptability or versatility
If a small bias voltage is used between output and input signals, then protocol standards are satisfied, but oscillation occurs during transitions
Solution Approach 1:
The patent implements dynamic bias voltage adjustment where the bias voltage is small during signal transitions to satisfy protocol standards, and large during stable states to prevent oscillation. The two operational amplifiers and associated switches dynamically adjust the bias voltage based on the transient state, resolving the contradiction between protocol compliance and oscillation control.
Solution Approach 2:
The patent uses feedback mechanisms where the first and second operational amplifiers continuously monitor the voltage difference between output and input signals and adjust their gate signals accordingly. The first comparator provides feedback to control the first switch based on the first voltage threshold, and the second comparator provides feedback to control the first switch based on the second voltage threshold. This feedback ensures protocol compliance during transitions while preventing oscillation during steady states.
4Object-affected harmful factors
If a small bias voltage is used between output and input signals, then oscillation is reduced, but transient response needs to be improved
Solution Approach 1:
The patent dynamically adjusts the bias voltage to be small during transient transitions to reduce oscillation and enable fast response, and large during stable operation to maintain signal integrity. The dynamic switching between small and large bias voltages based on transient state resolves the contradiction between oscillation reduction and transient response speed.
Solution Approach 2:
The patent applies preliminary action by proactively switching to a smaller bias voltage before and during signal transitions to prevent oscillation and enable fast transient response. The operational amplifiers and comparators detect transition conditions in advance and adjust the bias voltage accordingly, ensuring both oscillation reduction and fast response without compromising signal integrity.
Data Source
AI summary
A bi-directional buffer for applications using in an I2C or SMBUS or other bus systems. The bi-directional buffer has an input terminal to receive an input voltage signal and an output terminal for providing an output voltage signal, and the output voltage signal follows the input voltage signal. The output voltage signal is regulated to have a first bias voltage greater than the input voltage signal by a first operational amplifier, or to have a second bias voltage greater than the input voltage signal by a second operational amplifier, the second bias voltage is smaller than the first bias voltage.