Driver Output Slew Rate Compensation Using Delay and Phase Detection
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current techniques for controlling driver output slew rate variation are inadequate due to indirect compensation and lack of accuracy, particularly in high-frequency applications where tight specifications are required, and fail to account for across-chip and local power supply variations.
Innovation Solution
A method and apparatus that directly measures and controls driver output slew rate by using a delay circuit with a tunable delay line, comparators, and a phase detector to align phases and adjust the driver output slew rate based on measured transition times compared to a reference, enabling precise compensation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If indirect PVT correlation compensation is used, then device complexity is reduced, but measurement precision and control accuracy of slew rate deteriorate
Solution Approach 1:
The patent replaces indirect electrical correlation-based compensation with direct time-domain measurement and control. By substituting the mechanical/electrical measurement approach (voltage division and PVT correlation) with a direct time measurement system using delay circuits and phase detectors, the patent achieves superior slew rate control accuracy while maintaining practical device complexity.
2Reliability
If tight slew rate specifications are enforced, then signal integrity improves, but device complexity and compensation difficulty increase
Solution Approach 1:
The patent implements a closed-loop feedback system where the measured driver output transition time is continuously compared against a reference delay, and the phase detector generates correction signals to adjust the driver slew rate in real-time. This feedback mechanism enables tight slew rate control for signal integrity while avoiding the need for overly complex open-loop compensation circuits.
3Reliability
If PVT correlation techniques are used, then some compensation is achieved, but across-chip and local power supply variations are not accounted for
Solution Approach 1:
The patent employs local quality by placing individual delay circuits and phase detectors at each driver location across the chip. Each driver has its own dedicated measurement and control circuitry that locally senses transition times and applies specific compensation tailored to that location's unique PVT conditions, thereby achieving comprehensive coverage of across-chip and power supply variations.
Data Source
AI summary
Apparatus and method for controlling the driver output slew rate. The apparatus includes a driver circuit having an input signal and an output signal, where the driver circuit is structured and arranged to facilitate control of the slew rate of the output signal. A delay circuit having a time delay proportional to a desired transition time of the driver output signal is coupled to the output of the driver circuit. A first comparator detects when the driver output signal rises through a specified level, and a second comparator detects when the driver output falls through a second specified level. A phase detector is coupled to outputs of the first and second comparators and an output of the delay circuit for aligning the phases of the comparator outputs and the delayed comparator outputs by adjusting the driver output slew rate.