Off-Chip Driver Slew Rate Calibration Using Edge Pulse Comparison
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Solution Overview
Problem
Existing off-chip driver circuits face challenges in controlling slew rate due to variations in process, voltage, temperature, and output load, requiring costly manual calibration and complex systems with many elements.
Innovation Solution
A simplified apparatus and method that compares the peak magnitude values of actual and ideal edge transition pulses to adjust the slew rate of off-chip driver circuits using RC filters, rectifiers, comparators, and a bitstate counter to increment or decrement pre-driver strength.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If manual calibration with trial and error approach is used to configure pre-driver circuit, then slew rate control can be achieved, but implementation cost increases and operation complexity increases
Solution Approach 1:
The system performs self-calibration by automatically comparing actual slew rate with target slew rate and adjusting pre-driver configuration without requiring manual trial and error. The calibration circuit autonomously determines the optimal pre-driver setup based on measured performance.
Solution Approach 2:
The system implements a feedback mechanism where the actual slew rate is measured and compared with the target slew rate, and the difference is used to automatically adjust the pre-driver configuration. This closed-loop control eliminates manual calibration requirements.
2Extent of automation
If DLL-based slew rate control system is implemented, then automated slew rate control is achieved, but system complexity increases and additional components are required
Solution Approach 1:
The invention extracts and eliminates the complex DLL components from the slew rate control system, retaining only the essential calibration functionality. By removing the delay locked loop and its associated delay elements and phase comparators, the system achieves automation without the burden of complex additional components.
Solution Approach 2:
Instead of implementing a full DLL-based control system, the invention uses a simplified calibration circuit that copies only the necessary measurement and adjustment functions, achieving the same automated control goal with fewer components.
3Speed
If pre-driver strength is increased to compensate for slow slew rate, then transition speed improves, but power consumption increases
Solution Approach 1:
The system dynamically adjusts pre-driver strength based on actual performance measurements rather than using fixed maximum settings. This allows the pre-driver to operate at the minimum necessary strength to achieve target slew rate, optimizing the balance between transition speed and power consumption.
Solution Approach 2:
The invention changes the operational parameters of the pre-driver based on measured slew rate performance, adjusting the drive strength to match the specific requirements of each operating condition rather than always using maximum strength, thereby reducing unnecessary power consumption.
Data Source
AI summary
An apparatus for compensating slew rate of a driving circuit includes: a first circuit, for receiving an edge transition from the driving circuit and generating a first pulse proportional to an actual slope of the edge transition; a second circuit, for receiving an ideal edge transition of the driving circuit and generating a second pulse proportional to an ideal slope of the ideal edge transition; a comparison circuit, coupled to the first circuit and the second circuit, for comparing an extreme value of amplitude of the first pulse with an extreme value of amplitude of the second pulse to produce a comparison signal; and a control circuit, coupled to the comparison circuit, for increasing or decreasing the slew rate of the driving circuit according to the comparison signal.