Buffer Slew Rate Equalization for Clock Duty Cycle Accuracy
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Mismatched rise and fall slew rates in clocking signals can lead to timing errors and undesired duty cycle propagation in integrated circuits, particularly affecting input/output drivers and phase interpolators.
Innovation Solution
A method and system that measure and compare rise and fall slew rates at the input and output of a buffer, generating control signals to adjust the slew rates and equalize them, using a slew reference based on input slew rates to ensure synchronized output slew rates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a buffer is used to transmit clock signals, then signal transmission is achieved, but rise and fall slew rates become mismatched leading to timing errors
Solution Approach 1:
The patent implements feedback by measuring the actual rise and fall slew rates at the buffer output, comparing them against target values, and using the comparison results to generate control signals that adjust the buffer's slew rates. This closed-loop feedback mechanism continuously monitors and corrects slew rate mismatches, ensuring timing accuracy is maintained despite process variations or environmental changes.
Solution Approach 2:
The patent changes the electrical parameters of the buffer by dynamically adjusting its rise and fall slew rates through control signals. These control signals modify the buffer's internal transistor operating points or resistance values, allowing independent optimization of rise and fall transition speeds to achieve matched slew rates for improved timing reliability.
2Reliability
If slew rates are adjusted to match, then timing errors are reduced, but additional measurement and control circuits are required
Solution Approach 1:
The patent merges the slew rate measurement, comparison, and control functions into an integrated calibration system that works closely with the existing buffer structure. The measurement circuits are combined with the buffer output stage, and the control signals are integrated into the buffer's existing control input structure, reducing the need for separate standalone components and minimizing overall circuit complexity.
Solution Approach 2:
The buffer system performs self-calibration by automatically measuring its own slew rates and generating its own control signals for adjustment. The measurement circuits monitor the buffer's output directly, and the control logic is embedded within the same system, allowing the buffer to self-correct its performance without requiring external calibration equipment or complex external control circuitry.
Data Source
AI summary
Aspects of the invention provide for equalizing rise and fall slew rates at an output for a buffer. In one embodiment, a method includes: measuring, simultaneously, rise and fall slew rates at an input of the buffer and rise and fall slew rates at the output of the buffer; generating a slew reference based on at least one of the rise slew rate or the fall slew rate at the input of the buffer; comparing the rise slew rate and the fall slew rate at the output of the buffer to the slew reference; and generating at least one of a rise control signal or a fall control signal for adjusting at least one of the rise slew rate or the fall slew rate at the output of the buffer.