Self-Referenced DAC Calibration for INL Precision
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Solution Overview
Problem
Conventional digital-to-analog converters (DACs) require complex external circuitry for calibration, which can be cumbersome and inefficient, especially in achieving high precision due to stochastic and deterministic non-idealities.
Innovation Solution
A Built-In-Self-Test (BIST) and calibration system that uses self-referencing components to calibrate DAC linearity by comparing outputs in an analog environment and providing digital feedback to a digital signal processor, eliminating the need for external referencing components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional external calibration circuitry is used, then DAC calibration can be achieved, but device complexity and manufacturing cost increase
Solution Approach 1:
The patent combines the calibration functionality with the existing DAC structure by using the same DAC core for both normal operation and calibration measurements. The BIST circuit integrates comparison logic and control mechanisms within the DAC architecture, eliminating the need for separate external calibration equipment and reducing overall system complexity.
Solution Approach 2:
The DAC performs self-calibration through built-in self-test (BIST) circuitry that automatically measures and adjusts its own transfer function. The system uses internal resources including the DAC core, comparison logic, and control mechanisms to conduct calibration without requiring external referencing components or complex external circuitry.
2Manufacturing precision
If external referencing components are used for calibration, then DAC linearity can be measured, but manufacturing cost and device complexity increase
Solution Approach 1:
The DAC performs self-calibration through built-in self-test (BIST) circuitry that automatically measures and adjusts its own transfer function. The system uses internal resources including the DAC core, comparison logic, and control mechanisms to conduct calibration without requiring external referencing components or complex external circuitry.
Solution Approach 2:
The same DAC core is used for multiple purposes: normal signal conversion during operation and calibration measurements during self-test. This multi-functionality eliminates the need for dedicated calibration hardware, reducing component count and manufacturing complexity while maintaining calibration accuracy.
3Productivity
If floating-point to fixed-point conversion processes are used, then digital signal processing can be performed, but precision is reduced
Solution Approach 1:
The patent replaces floating-point arithmetic operations with fixed-point arithmetic in the digital signal processing portion of the system. By carefully designing the fixed-point representation and using integer-based calculations, the system maintains sufficient precision for calibration measurements while improving computational efficiency and reducing the complexity of floating-point to fixed-point conversion processes.
Data Source
AI summary
In contrast to some existing techniques, a calibration technique compares multiple outputs which may be, for example, successive or different outputs from the digital-to-analog converter (DAC) in an analog environment and determines differences between at least two outputs in an analog environment. A feedback signal is provided in the digital environment to provide an internal or self-calibration regime. The digital feedback signal is provided to a digital signal processing (DSP) component of the calibration circuitry which uses the feedback signal to determine appropriate input codes to provide to the DAC. The same DAC can be used for both signal generation and feedback DAC purposes, and this provides a self-calibration of the DAC performance which is typically related to the integral non-linearity (INL) characteristics of the DAC transfer function.