Switched Capacitor Level Shifting With Lower Op-Amp Load
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Solution Overview
Problem
Switched capacitor circuits configured with the CLS technique face increased power consumption due to the additional load imposed by the level shift capacitor, which can limit the operational amplifier's performance and increase power usage.
Innovation Solution
The level shift capacitor is strategically connected between the output of the last operational amplifier stage and the output terminal, also functioning as a phase compensation capacitor in the estimate phase, reducing the load on the operational amplifier and minimizing power consumption by distributing the phase compensation role across multiple capacitors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the CLS technique is used to achieve high precision and large gain, then the output accuracy is improved, but the power consumption increases due to the additional load from the level shift capacitor
Solution Approach 1:
The level shift capacitor is made to serve dual functions: it performs level shifting of the output signal while simultaneously acting as a phase compensation capacitor for the operational amplifier. This multi-functionality eliminates the need for a separate phase compensation capacitor, thereby reducing the total capacitance load on the operational amplifier and lowering power consumption while maintaining the precision benefits of the CLS technique
Solution Approach 2:
The level shift function and phase compensation function are merged into a single capacitor component. By combining these two functions into one element, the circuit reduces component count and total capacitance load, which directly addresses the power consumption issue while preserving the accuracy improvements from the CLS technique
2Power
If the level shift capacitor is added to the CLS circuit, then the output amplitude is increased, but the load on the operational amplifier increases causing higher power consumption
Solution Approach 1:
The level shift capacitor performs dual roles: level shifting to increase output amplitude and phase compensation to reduce the effective load on the operational amplifier. This multi-functionality allows the circuit to achieve higher output amplitude without the proportional increase in power consumption that would otherwise result from additional capacitance loading
3Stability of the object's composition
If a separate phase compensation capacitor is added to the operational amplifier, then the stability is improved, but the circuit complexity and power consumption increase
Solution Approach 1:
The level shift capacitor is designed to provide both level shifting and phase compensation functions. By making this single capacitor serve multiple purposes, the circuit achieves operational amplifier stability without adding separate compensation components, thereby maintaining circuit simplicity while ensuring stable operation
Solution Approach 2:
The phase compensation function is merged into the level shift capacitor's operation. This consolidation eliminates the need for a separate phase compensation capacitor, reducing circuit complexity and component count while maintaining the stability requirements for proper operational amplifier function
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 configuration significantly reduces power consumption in switched capacitor circuits while maintaining high precision and large gain, even with a low-power operational amplifier, and decreases the overall circuit size and manufacturing costs.
Implementation Method 1
The capacitors C1 and C2 are sampling capacitors which are respectively connected to the switches SW1 to SW5, and which are made to store and hold charge corresponding to the analog input signal Vin by the switching of connection states of the switches SW1 to SW5
Implementation Method 2
The operational amplifier AMP1 is configured to amplify the analog input signal Vin sampled and held by the capacitors C1 and C2, according to the amplification degree based on the gain A and the feedback amount based on the loop feedback coefficient β
Data Source
AI summary
There is provided a switched capacitor circuit and a pipeline A/D converter which are capable of suppressing electric power from being increased by utilizing a level-shift capacitor, even in a case where the switched capacitor circuit and the pipeline A/D converter are configured by utilizing a CLS technique. In the estimate phase, the capacitor Cc1 (level shift capacitor) is connected between the output terminal of the operational amplifier AMP2 and the inverting input terminal of the operational amplifier AMP2, so as to sample the output from the operational amplifier AMP2, and also to compensate the phase of the operational amplifier AMP2. Additionally, in the level shift phase, the capacitor Cc1 is connected between the output terminal of the operational amplifier 4 and the output terminal Vb, so as to be used to level-shift the output of the operational amplifier AMP2. Thereby, the load (the capacitance of the capacitors Cc1 and Cc2) on the operational amplifier AMP2 is reduced, thereby reducing the electric power of the switched capacitor circuit 200.