Slew Rate Control Circuit With Compensation for Low-Delay Switching
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Faster switching ON/OFF in integrated circuits leads to issues like SSO noise, crosstalk, EMI, and increased propagation delay, which are mitigated by slew rate control but result in undesirable delays.
Innovation Solution
A compensation circuit is enabled at the beginning of a driving signal's edge to speed up transistor switching in the output circuit, reducing propagation delay, and then disabled when the edge starts to rise or fall, allowing controlled slew rate management.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If slew rate control is applied to mitigate SSO noise, crosstalk, and EMI, then electromagnetic interference is reduced, but propagation delay increases
Solution Approach 1:
The compensation circuit is enabled at the beginning of a first edge of a driving signal to speed up switching of a transistor in an output circuit before the main signal transition occurs. This preliminary action reduces the propagation delay of the output signal edge while the slew rate control circuit subsequently controls the slew rate of the output signal to mitigate SSO noise, crosstalk, and EMI.
Solution Approach 2:
The solution segments the signal transition process into two distinct phases: (1) an initial phase where the compensation circuit speeds up transistor switching to reduce propagation delay, and (2) a subsequent phase where the slew rate control circuit manages the slew rate to control electromagnetic interference. This segmentation allows both objectives to be achieved in sequence without conflict.
2Speed
If switching speed is increased to improve IC performance, then speed performance is improved, but SSO noise and crosstalk increase
Solution Approach 1:
The compensation circuit provides a preliminary speed boost to the transistor switching process, allowing the output signal to start transitioning faster. This reduces the overall propagation delay while the subsequent slew rate control phase manages the electromagnetic interference generated by the fast switching.
Solution Approach 2:
The system dynamically adjusts the switching behavior in two stages: first allowing fast switching through the compensation circuit to improve speed performance, then transitioning to controlled slew rate management to mitigate the harmful electromagnetic effects. This dynamic approach adapts the switching characteristics to different phases of the signal transition.
Data Source
AI summary
In a method of operating a circuit, at a beginning of a first edge of a driving signal, a first transistor is turned ON to pull, at a first changing rate, a voltage of the driving signal on the first edge from a first voltage toward a second voltage. Then, in response to the voltage of the driving signal on the first edge reaching a threshold voltage between the first voltage and the second voltage, the first transistor is turned OFF and an output circuit is caused to start a second edge of an output signal in response to the first edge of the driving signal. The second edge has a slew rate corresponding to a second changing rate of the voltage of the driving signal on the first edge from the threshold voltage toward the second voltage. The second changing rate is controlled by a passive circuit and is smaller than the first changing rate.