On-Die Termination Feedback Calibration for Offset-Stable Code Values
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Solution Overview
Problem
Conventional on-die termination circuits in semiconductor memory apparatuses suffer from offset voltages that cause unstable comparison results and erroneous code values, leading to impedance mismatches and signal loss due to impedance mismatch.
Innovation Solution
An on-die termination circuit with a comparing block, counting block, and controlling block that compares a reference voltage with a code voltage, generates comparison signals, and adjusts counting operations based on previous and current match results to prevent abnormal code value changes, using D/A converters, comparators, counters, and control units to maintain accurate code values.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional on-die termination circuit uses comparator to compare reference voltage with code voltage, then impedance matching can be achieved, but offset voltage causes unstable comparison results and erroneous code values
Solution Approach 1:
The patent introduces a feedback mechanism where the comparison result is fed back to the code adjustment circuit. The code adjustment circuit adjusts the code value based on the comparison result to compensate for offset voltage effects. This closed-loop feedback system continuously corrects the code value to maintain accurate impedance matching despite comparator offset voltages.
Solution Approach 2:
The on-die termination circuit performs self-calibration by using its own comparison output to adjust its own code values. The code adjustment circuit automatically compensates for offset errors without requiring external calibration equipment, making the system self-correcting and eliminating the need for external calibration processes.
2Measurement precision
If on-die termination adjusts code values to compensate for offset voltage, then measurement precision improves, but device complexity increases due to additional control circuits
Solution Approach 1:
The code adjustment circuit serves multiple functions: it acts as a digital-to-analog converter, implements feedback control, performs offset compensation, and adjusts termination impedance. By combining these functions into a single multi-functional block, the patent reduces overall circuit complexity while maintaining high measurement precision.
Solution Approach 2:
The patent merges the code adjustment circuit with the existing on-die termination structure, integrating the feedback control and offset compensation functions into the termination circuit itself. This consolidation eliminates the need for separate calibration circuits and reduces the overall device complexity.
Data Source
AI summary
An on-die termination circuit in a semiconductor memory apparatus can comprise a comparing block for comparing a reference voltage with a code voltage corresponding to a code and outputting a comparison signal, a counting block for changing the code based on the comparison signal, and controlling block for controlling the counting block based on a match result of previous and current values of the comparison signal.