DAC Regulator with Variable Resistances for Voltage Step Uniformity
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Solution Overview
Problem
Digital-to-analog converters, particularly R-2R type converters used in Flash-type memories, face issues with non-uniform voltage steps due to resistance variations, leading to anomalous programming and degradation of multi-level memory reliability, especially when changes occur in the most significant bits of the input digital signal.
Innovation Solution
A regulator for digital-to-analog converters is designed with variable resistances in each circuit branch, calibrated by a calibration circuit to ensure uniform voltage steps, using a device that measures the analog signal and adjusts the resistances to compensate for differences, thereby maintaining consistent voltage steps across all operating conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If fixed resistances are used in the R-2R converter branches, then the device complexity is reduced, but the voltage step uniformity deteriorates due to resistance variations
Solution Approach 1:
The patent applies the dynamics principle by replacing fixed resistances with variable resistances in the R-2R converter branches. Each variable resistance can be adjusted individually to compensate for manufacturing tolerances and ensure uniform voltage steps across all digital input transitions, thereby resolving the contradiction between simplified structure and precise voltage uniformity.
Solution Approach 2:
The patent implements parameter changes by allowing the resistance values in the converter branches to be varied through calibration. The variable resistances enable adjustment of the resistance parameter to achieve the desired voltage step uniformity, addressing the manufacturing precision issue while maintaining the overall R-2R converter architecture.
2Manufacturing precision
If variable resistances are added to each branch for calibration, then the voltage step uniformity is improved, but the device complexity increases
Solution Approach 1:
The patent applies local quality by introducing variable resistances specifically in the branches corresponding to the most significant bits, where resistance variations have the greatest impact on voltage step uniformity. This targeted approach improves voltage uniformity while minimizing the overall increase in device complexity compared to making all resistances variable.
Solution Approach 2:
The patent implements preliminary action through a calibration process that adjusts the variable resistances before the converter is put into normal operation. The calibration circuit measures the actual voltage steps and adjusts the variable resistances to compensate for manufacturing variations, ensuring uniform voltage steps are achieved before the device is used, thereby managing complexity through a one-time setup process.
3Measurement precision
If resistance variations occur in the most significant branches, then the voltage step accuracy deteriorates, but adding calibration circuits increases the manufacturing complexity
Solution Approach 1:
The patent applies self-service by implementing an automatic calibration process where the converter uses its own output to measure and adjust its internal resistances. The calibration circuit measures the voltage steps generated by the converter and automatically adjusts the variable resistances to achieve uniformity, eliminating the need for external manual calibration and simplifying the manufacturing process despite the added circuitry.
Data Source
AI summary
A regulator for a digital-to-analog converter having in input a digital signal and suitable for providing an analog signal in output, the regulator including at least one pair of buffers having in input the digital signal and the outputs connected to a pair of circuit branches connected to the output of the regulator; each of the at least two circuit branches having at least one resistance. To at least one of the at least one pair of buffers a variable resistance is associated, and the regulator includes a circuit having in input the analog signal and adapted for measuring its waveform and acting on the variable resistance in response to its possible anomalous waveform compared to a desired waveform.