RDAC Reference Tuning for Temperature-Stable SAR ADC Calibration
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing analog-to-digital converters, particularly successive approximation register (SAR) ADCs, suffer from temperature-dependent errors due to process variations among transistors, leading to gain differences among SAR slices, which cannot be separately adjusted or calibrated without introducing additional temperature variations.
Innovation Solution
The implementation of a resistor digital-to-analog converter (RDAC) with a global reference circuit and independently controllable switches, allowing for temperature-independent voltage adjustments to each SAR slice, enabling precise calibration and compensation of gain differences without affecting temperature stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If separate voltage adjustments are added to each SAR slice to compensate for gain differences, then manufacturing precision is improved, but device complexity increases
Solution Approach 1:
The RDAC is designed as a universal circuit that can be replicated across multiple SAR slices, providing both voltage adjustment and temperature compensation functions through a single standardized block. This multi-functional approach enables gain matching across slices without requiring different circuit implementations for each slice, thus improving manufacturing precision while controlling device complexity through reuse.
Solution Approach 2:
The RDAC adjusts the reference voltage parameter (VREF) to compensate for gain differences among SAR slices. By changing the voltage parameter through digital control of switch configurations, the circuit achieves precise gain matching without adding complex analog adjustment mechanisms, resolving the contradiction between precision and complexity.
2Manufacturing precision
If voltage adjustments are implemented to compensate for process variations, then manufacturing precision is improved, but temperature stability deteriorates
Solution Approach 1:
The RDAC dynamically adjusts the reference voltage parameter to compensate for temperature-induced drift in SAR slice outputs. By changing the voltage parameter in response to temperature variations, the system maintains both manufacturing precision and temperature stability, resolving the contradiction between these two requirements.
Solution Approach 2:
The system uses feedback from temperature sensing and output voltage monitoring to dynamically adjust the RDAC reference voltage. This feedback mechanism ensures that voltage adjustments maintain precision across temperature variations without introducing instability, as the adjustments are continuously optimized based on actual operating conditions.
3Manufacturing precision
If RDAC with independent voltage adjustment is added to each slice, then manufacturing precision is improved, but device complexity increases
Solution Approach 1:
The solution segments the voltage adjustment function into discrete, independently controllable RDAC units, each associated with a specific SAR slice. This segmentation allows precise individual calibration of each slice while maintaining a modular architecture that manages complexity through standardization and replication of identical functional blocks.
Solution Approach 2:
The RDAC circuit is designed as a universal, replicated block that performs multiple functions: reference voltage generation, gain adjustment, and temperature compensation. By making this single circuit design universal across all slices, the system achieves high manufacturing precision without proportionally increasing overall device complexity, as the same standardized block is reused throughout the architecture.
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 solution ensures that the output voltages of different SAR slices remain constant and individually tunable across temperature variations, effectively addressing the temperature-dependent errors and providing a mechanism for compensating fabrication-related mismatches without introducing additional temperature variations.
Implementation Method 1
a resistor digital-to-analog converter (RDAC) with a global reference circuit and independently controllable switches, allowing for temperature-independent voltage adjustments
Data Source
AI summary
Circuits for an analog-to-digital converter and methods of operating an analog-to-digital converter. A resistor digital-to-analog converter (RDAC) has a first reference node coupled to a first current source, a second reference node coupled to a second current source, an input port configured to receive a first voltage, and an output port coupled to a buffer. The RDAC is configured to generate a second voltage including a first voltage shift from the first voltage and to supply the second voltage from the output port of the RDAC to the buffer.