SAR ADC Timing Control With Bit-Dependent DAC Settling
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Solution Overview
Problem
Conventional analog-to-digital conversion methods are often slow and inaccurate, particularly in successive approximation register (SAR) converters.
Innovation Solution
The implementation of a SAR ADC system that dynamically adjusts DAC settling times based on bit positions within the digital output code, using a DAC settling timer with adjustable RC circuits to optimize conversion speed while maintaining effective number of bits (ENOB), by allocating more time for significant bits and less time for less significant bits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If conventional SAR ADC methods use uniform settling time for all bits, then the conversion process is simple to implement, but the conversion speed is slow and accuracy is limited
Solution Approach 1:
The patent applies dynamics by making the settling time variable rather than fixed. The settling time is dynamically adjusted based on the bit position being converted, with different settling times allocated for different bits. This dynamic adjustment optimizes the conversion speed for each bit while maintaining accuracy, directly resolving the contradiction between conversion speed and implementation complexity.
Solution Approach 2:
The patent changes the parameter of settling time from a uniform constant to a variable parameter that depends on bit position. By modifying this key parameter, the system achieves faster conversion speeds for less significant bits while maintaining adequate settling time for significant bits, thereby improving overall conversion speed without sacrificing accuracy.
2Measurement precision
If more settling time is allocated for all bits, then measurement precision improves, but conversion speed decreases
Solution Approach 1:
The patent applies local quality by allocating different settling times to different bit positions based on their specific requirements. Less settling time is allocated to less significant bits where high precision is less critical, while adequate settling time is maintained for significant bits. This localized optimization improves overall conversion speed while maintaining the effective number of bits.
Solution Approach 2:
The patent uses partial action by providing more than sufficient settling time only when necessary (for significant bits), and reducing settling time for less critical operations (less significant bits). This selective allocation of settling time resources achieves the required measurement precision while minimizing total conversion time.
3Ease of manufacture
If uniform settling time is used for all bit positions, then the design is simple, but conversion accuracy and speed are compromised
Solution Approach 1:
The patent applies segmentation by dividing the conversion process into distinct stages, each handling a specific bit position with its own optimized settling time. This segmentation allows each bit conversion to be independently optimized, improving overall conversion accuracy and speed while maintaining a structured, manageable design approach.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach enhances the speed of analog-to-digital conversion while maintaining high ENOB, primarily by determining the timing margin with least significant bits, thereby improving the overall efficiency of the conversion process.
Implementation Method 1
a DAC settling timer with adjustable RC circuits to optimize conversion speed
Data Source
AI summary
Aspects of a method and apparatus for converting an analog input value to a digital output code are provided. One embodiment of the apparatus includes a digital-to-analog converter, a comparator, and control logic circuitry. The digital-to-analog converter is configured to generate an analog reference value based on a received digital reference value. The comparator is configured to compare an analog input value to the analog reference value after expiration of an allotted settling time for the digital-to-analog converter and generate a comparison result indicative a relationship between the analog input value and the analog reference value. The control logic circuitry is configured to select the allotted settling time for the digital-to-analog converter based on a bit position of a digital output code to be determined, and update the bit position of the digital output code based on the comparison result.