Successive Approximation ADC with Flash-Based Initial D/A Range Setting
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Solution Overview
Problem
Successive approximation analog-to-digital converters face challenges in accurately converting analog signals at low voltage conditions due to comparator operational limitations, leading to potential non-linearity and reduced accuracy.
Innovation Solution
The implementation of a multi-bit flash A/D converter and successive approximation logic that determines an initial D/A value to keep the output within the comparator's operational range, using a capacitive D/A converter and a voltage regulator to minimize offset drift and ensure accurate conversions across varying supply voltages.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If a conventional successive approximation A/D converter is used, then the converter can operate at low voltage conditions, but the comparator operational limitations cause non-linearity and reduced accuracy
Solution Approach 1:
The patent applies preliminary action by determining an initial D/A value before the main successive approximation process begins. This initial value is calculated based on the input voltage range to ensure that the comparator operates within its linear region from the start, preventing non-linearity issues that would otherwise occur at low voltage conditions.
Solution Approach 2:
The patent changes the operating parameters by adjusting the D/A converter output range dynamically. By modifying the initial D/A value based on the input voltage range and ensuring the comparator operates within its optimal voltage swing range, the system maintains high accuracy across varying supply voltages without being constrained by low voltage limitations.
2Measurement precision
If the D/A converter output range is increased to improve resolution, then the signal level increases, but the comparator may operate outside its optimal range causing non-linearity
Solution Approach 1:
The patent dynamically adjusts the D/A converter output parameters to match the comparator's optimal operating range. By calculating an appropriate initial D/A value based on the input voltage and scaling it to fit within the comparator's linear region, the system maintains both high signal resolution and reliable linear operation across different operating conditions.
3Measurement precision
If voltage regulation is added to maintain comparator operating range, then accuracy is improved, but circuit complexity and area increase
Solution Approach 1:
The patent makes the existing D/A converter multi-functional by having it serve both as the primary conversion element and as a voltage regulation mechanism. The initial D/A value calculation and output scaling functions replace the need for separate voltage regulation circuitry, maintaining high conversion accuracy while avoiding additional circuit area and complexity.
Solution Approach 2:
The system performs self-regulation by using its own D/A converter to generate the appropriate voltage levels for comparator operation. Rather than requiring external voltage regulation components, the converter automatically adjusts its output range to ensure the comparator operates within its optimal region, reducing overall circuit complexity.
Data Source
AI summary
In accordance with an embodiment, a method of performing a successive approximation analog-to-digital (A/D) conversion includes determining a voltage range of an analog input voltage in a single cycle using a multi-bit flash A/D converter, determining an initial D/A value for a successive approximation based on determining the voltage range, and successively approximating the analog input voltage. Successively approximating includes providing the initial D/A value to a D/A converter, comparing an output of the D/A converter with the analog input voltage, and determining a further D/A value based on the comparing.