Voltage Reference Programmable Output Resistance Linearity
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Solution Overview
Problem
Voltage references face challenges in maintaining linearity due to variable impedance characteristics at the output node, primarily caused by differences in effective series resistance of decoupling capacitors across different fabrication batches, leading to non-linear output voltage variations with load current changes.
Innovation Solution
Incorporating a programmable resistance portion at the output node, which is either hard-programmed or dynamically adjusted based on sampling frequency to match the output resistance of the voltage reference with the series resistance of the output capacitor, ensuring improved linearity by minimizing non-linearity caused by fabrication variations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If decoupling capacitors are used at the output node, then stability is improved, but impedance characteristics vary across fabrication batches leading to non-linearity
Solution Approach 1:
The patent applies parameter changes by making the output resistance programmable and adjustable. The system measures the actual output resistance of the voltage reference circuit and programs the programmable output resistance to match this measured value, thereby compensating for fabrication variations in decoupling capacitor ESR and achieving consistent impedance characteristics across different manufacturing batches.
2Device complexity
If output resistance is fixed, then circuit simplicity is maintained, but linearity deteriorates due to mismatch with varying load conditions
Solution Approach 1:
The patent implements dynamics by making the output resistance programmable and adjustable based on operating conditions. The system measures the output resistance at different frequencies and loads, then programs the programmable output resistance accordingly to maintain optimal matching with the decoupling capacitor ESR across varying load conditions and frequencies.
Solution Approach 2:
The patent applies feedback by measuring the actual output resistance of the voltage reference circuit and using this measurement to program the programmable output resistance. This closed-loop approach ensures that the total output resistance matches the decoupling capacitor ESR, thereby maintaining linearity and compensating for fabrication variations.
3Reliability
If programmable resistance is added to match impedance, then linearity is improved, but device complexity increases
Solution Approach 1:
The patent uses an intermediary approach by introducing a programmable output resistance element that acts as a mediator between the fixed voltage reference circuit and the decoupling capacitor. This programmable resistance can be adjusted to match the ESR of the decoupling capacitor, thereby improving linearity without requiring fundamental changes to the core voltage reference circuit architecture.
Data Source
AI summary
A voltage reference containing a programmable resistance portion at an output node at which an output reference voltage is provided. The desired magnitude of the programmable portion which provides optimum matching of an output resistance of the voltage reference and a series resistance of an output capacitor of the voltage reference is determined and hard-programmed. As a result, the output voltage of the voltage reference is provided with improved linearity. In an embodiment, the determination of the magnitude of the programmable portion is performed by providing an input to an analog to digital converter (ADC) with the voltage reference driving the ADC. The resistance setting corresponding to the third harmonic being less than a desired threshold is then hard-programmed. In an alternative embodiment, the programmable portion is set to specific resistance dynamically during operation.