Slew Rate Control Circuit With Edge Compensation for Lower Delay
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Solution Overview
Problem
Faster switching speeds in integrated circuits lead to issues like SSO noise, crosstalk, and EMI, which are partially mitigated by slew rate control, but this approach increases propagation delay, affecting speed performance.
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 by controlling the slew rate of the output signal, and is disabled when the second edge of the output signal starts to rise or fall, allowing the slew rate to be controlled by the changing rate of the driving signal's voltage.
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 the first edge of the driving signal to perform preliminary action by speeding up transistor switching before the output signal edge transitions. This preliminary speed-up action reduces propagation delay while the slew rate control circuit subsequently controls the transition rate to mitigate electromagnetic interference
Solution Approach 2:
The system dynamically switches between two modes: initially using the compensation circuit to reduce delay, then transitioning to slew rate control for EMI mitigation. The compensation circuit is disabled when the output signal edge starts to rise or fall, creating a dynamic, time-varying control strategy that optimizes both speed and interference reduction
Data Source
AI summary
A circuit includes a driver circuit configured to generate a driving signal having a first edge, an output circuit coupled to the driver circuit via a connection to receive the driving signal on the connection, and a compensation circuit coupled to the connection. The output circuit is configured to generate an output signal in response to the driving signal. A second edge of the output signal has a slew rate corresponding to a changing rate of a voltage of the driving signal on the first edge. The compensation circuit is configured to be enabled at a beginning of the first edge to pull the voltage of the driving signal on the first edge toward a threshold voltage. The compensation circuit is further configured to be disabled in response to and after the voltage of the driving signal on the first edge reaching the threshold voltage.