Reference Precharge Circuit for Low-Power Accurate ADC Biasing
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
High-performance systems face challenges in providing stable reference voltages for ADCs due to power consumption issues in precharge buffers, which can introduce errors in delta-sigma ADCs, and existing solutions either consume excessive power or lack accuracy in precharging the feedback DAC capacitor.
Innovation Solution
A reference precharge circuit comprising a gain amplifier, comparator, reservoir capacitor, logic circuit, current source, common mode feedback loop, and switching network, which uses a current source and comparator to charge the reservoir capacitor with reduced power consumption and improves precharge accuracy by leveraging the comparator's time delay for additional gain.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If operational amplifiers are used in the precharge buffer, then the precharge function is provided, but power consumption increases significantly
Solution Approach 1:
The patent extracts the essential precharge function from the operational amplifier and implements it using a simplified circuit consisting of a precharge buffer, reservoir capacitor, and control switches. This removes the high-power operational amplifier while retaining the necessary precharge capability, directly resolving the contradiction between providing precharge function and reducing power consumption.
Solution Approach 2:
The patent uses a simple precharge buffer circuit with a reservoir capacitor that is activated only when needed (during integration operation) and then discarded until the next precharge cycle. This temporary, on-demand approach replaces the continuously active operational amplifier, reducing overall power consumption while maintaining precharge functionality when required.
2Stability of the object's composition
If reservoir capacitor is added to reduce voltage dip, then voltage stability improves, but power consumption increases
Solution Approach 1:
The reservoir capacitor is pre-charged to the reference voltage before the integration operation begins. This preliminary charging action stores energy in the capacitor, which then naturally discharges to supply the feedback DAC capacitor during integration, providing voltage stability without requiring continuous power consumption from an operational amplifier.
Solution Approach 2:
The reservoir capacitor serves itself by being charged during the precharge phase and then automatically discharging to maintain voltage stability during integration. This self-service mechanism eliminates the need for continuous active power consumption, resolving the contradiction between voltage stability and power consumption.
3Measurement precision
If gain is added to the precharge buffer to improve precharge accuracy, then precharge accuracy improves, but power consumption increases even more
Solution Approach 1:
The patent introduces a comparator as an intermediary device that compares the reservoir capacitor voltage with the reference voltage and generates a control signal for the precharge buffer. This intermediary approach enables precise control of the precharge operation without requiring high gain amplification, thereby achieving precharge accuracy while maintaining low power consumption.
Solution Approach 2:
The comparator provides feedback by continuously monitoring the reservoir capacitor voltage and controlling the precharge buffer activation. This feedback mechanism ensures accurate precharging without requiring high gain, as the feedback loop naturally regulates the charging process, resolving the contradiction between precharge accuracy and power consumption.
4Reliability
If precharge buffer is used to reduce switching load, then ADC performance improves, but reference voltage dips during feedback capacitor coupling
Solution Approach 1:
The precharge buffer pre-charges the reservoir capacitor to the reference voltage before the integration operation begins. This preliminary action ensures that when the feedback capacitor couples to the reference voltage, the reservoir capacitor can naturally discharge to supply the required charge, preventing voltage dips and maintaining reference voltage stability while enabling ADC performance.
Data Source
AI summary
A precharge circuit comprises a gain amplifier, a comparator, a reservoir capacitor, a switch, a current source, and a switching network. The gain amplifier has a gain G1 and receives an input voltage Vrefp. The gain amplifier outputs an amplified voltage G1Vrefp to the comparator, which compares G1Vrefp to a voltage across the reservoir capacitor. The comparator outputs a control signal for the switch based on the comparison. The switch couples the current source to the reservoir capacitor. The current from the current source charges the reservoir capacitor. The switching network couples the reservoir capacitor to an output of the precharge circuit during a first operating mode and provides the input voltage Vrefp to the output during a second operating mode.