Output Driver Calibration Using Averaged Counts for Impedance Matching
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Solution Overview
Problem
As operational speeds of electronic devices increase, impedance mismatches between semiconductor devices and transmission networks lead to decreased transmission speed and distorted data, causing setup/hold failures and errors, which conventional impedance matching techniques are inadequate to address.
Innovation Solution
A calibration circuit and method for adjusting the impedance of output drivers in semiconductor devices, using pull-up and pull-down variable impedance circuits and comparators to generate averaged count signals for precise impedance matching, allowing for trimming of output impedance post-fabrication.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional processing controls are used to control output driver impedance, then manufacturing simplicity is maintained, but impedance matching precision deteriorates at high transmission data rates
Solution Approach 1:
The patent applies preliminary action by performing impedance calibration during a test period before normal operation begins. The calibration circuit measures actual impedance characteristics and adjusts trim elements to optimize impedance matching in advance, ensuring high-precision impedance control without adding complexity to the manufacturing process itself.
Solution Approach 2:
The patent implements parameter changes by introducing trimable elements (such as trimmable resistors or capacitors) that allow post-fabrication adjustment of impedance parameters. During calibration, these parameters are modified to achieve optimal impedance matching, enabling precise control without changing the fundamental manufacturing process.
2Productivity
If transmission data rates are increased to improve productivity, then data transmission speed improves, but impedance mismatches worsen causing distortion and errors
Solution Approach 1:
The patent implements feedback by using a calibration circuit that measures the actual impedance characteristics of the output driver and uses this information to adjust trim elements. This closed-loop feedback mechanism ensures that impedance matching is optimized based on actual performance, maintaining reliability even at high transmission data rates.
Solution Approach 2:
The patent applies preliminary action by performing impedance calibration during a test period before normal operation begins. This advance optimization ensures that the output driver is properly tuned for high-speed operation, preventing distortion and errors that would otherwise occur at high data rates.
3Reliability
If output driver impedance is made adjustable to improve impedance matching, then transmission reliability improves, but device complexity increases
Solution Approach 1:
The patent extracts the impedance adjustment function into a separate calibration circuit that operates independently during a test period. This separation allows the output driver to remain simple during normal operation while providing adjustability when needed, minimizing the impact on device complexity.
Solution Approach 2:
The patent performs impedance calibration during a test period before normal operation, extracting the complexity of impedance adjustment to a preliminary setup phase. This allows the output driver to maintain simple operation during data transmission while still achieving high reliability through pre-calibration.
Data Source
AI summary
A method, system, and output driver calibration circuit determine calibration values for configuring adjustable impedance output drivers. The calibration circuit includes a pull-up calibration circuit configured to generate an averaged pull-up count signal for calibrating p-channel devices in the output driver with the averaged pull-up count signal being an average of a plurality of pull-up count signals. The calibration circuit further includes a pull-down calibration circuit configured to generate an averaged pull-down count signal for calibrating n-channel devices in the output driver with the averaged pull-down count signal being an average of a plurality of pull-down count signals.