SAR ADC Compensation Circuit for Voltage Reference Stability
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Solution Overview
Problem
The accuracy of successive-approximation ADC circuitry is compromised due to voltage reference fluctuations caused by charge switching operations, leading to noise and distortion, which limits the frequency of operation and introduces inaccuracies.
Innovation Solution
Incorporating compensation circuitry with controllable parameters to adjust the charge injected into the voltage reference, matching the drawn and injected charges, thereby reducing settling time and noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If charge switching operations are performed in successive-approximation ADC circuitry, then conversion speed and frequency of operation are improved, but voltage reference fluctuations occur causing noise and distortion that compromise accuracy
Solution Approach 1:
The compensation circuit pre-charges the voltage reference node before the charge switching operations begin, creating a preliminary counter-action that offsets the upcoming charge draw. This preemptive measure reduces the voltage reference fluctuation that would otherwise occur during the conversion process, thereby maintaining accuracy while allowing fast operation.
Solution Approach 2:
The compensation circuit acts as an intermediary between the charge switching circuitry and the voltage reference. It mediates the interaction by providing a compensating charge that balances the charge drawn during switching operations, isolating the voltage reference from direct exposure to large charge transients and thus reducing noise and distortion.
2Productivity
If charge switching operations are performed at higher frequencies, then productivity and operation frequency are improved, but settling time increases and noise is introduced
Solution Approach 1:
The compensation circuit performs preliminary charging of the voltage reference node before the main charge switching operations. This advance preparation ensures that the voltage reference is already partially charged, reducing the time required for it to settle after charge switching occurs, thereby enabling higher operation frequencies without sacrificing stability.
3Measurement precision
If compensation circuitry is added to reduce voltage reference fluctuations, then accuracy and noise performance are improved, but device complexity increases
Solution Approach 1:
The compensation circuit adjusts the compensation charge parameter dynamically based on the conversion stage and requirements. By varying the compensation charge amount and timing, the circuit achieves accurate voltage reference compensation without requiring overly complex circuitry, optimizing the balance between accuracy and simplicity.
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 operation, reduces noise, and improves the accuracy of the ADC circuitry by minimizing voltage reference fluctuations, allowing for increased frequency and stability.
Implementation Method 1
compensation circuitry comprising at least one compensation capacitor and configured, in a precharge operation prior to the subconversion operation, to connect the at least one compensation capacitor so that the at least one compensation capacitor stores a compensation charge
Data Source
AI summary
Analogue-to-digital converter, ADC, circuitry including: successive-approximation circuitry configured in a subconversion operation to draw a charge from a first voltage reference, REF1; compensation circuitry including a compensation capacitor and configured, in a precharge operation, to connect the compensation capacitor so that the compensation capacitor stores a compensation charge, and, in the subconversion operation, to connect the compensation capacitor to the first voltage reference so that a charge is injected into the first voltage reference, REF1; and control circuitry, wherein: the successive-approximation circuitry and the compensation circuitry are configured such that one or more parameters defining at least one of said charges are controllable; and the control circuitry is configured to adjust at least one said parameter to adjust an extent to which the charge injected into the first voltage reference, REF1, by the compensation circuitry compensates for the charge drawn from the first voltage reference, REF1, by the successive-approximation circuitry.