Differential SAR ADC Charge Balancing for Constant Common Mode
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Solution Overview
Problem
Differential SAR analog-digital converters face challenges in maintaining a constant input common mode voltage, which affects decision accuracy and conversion speed, often requiring larger electronic components and increased power consumption to mitigate these issues.
Innovation Solution
The implementation of a differential analog-digital converter with charging and discharging units on each input signal line, where the control unit selectively switches these units to either increase or decrease the potential on one line while decreasing the other, thereby maintaining a constant input common mode voltage by adjusting the charge accordingly.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If capacitors are switched to positive reference potential during conversion phase, then conversion accuracy is improved, but input common mode voltage increases causing latch noise and reduced conversion speed
Solution Approach 1:
The patent applies counterweight principle by introducing discharging units that remove charge from input signal lines. When charging units add charge to increase potential, discharging units simultaneously remove charge to counterbalance the effect, thereby maintaining the input common mode voltage constant and preventing the voltage increase that would otherwise occur during conversion phase
Solution Approach 2:
The patent changes the operational parameters of the capacitor banks by introducing dual control modes: charging mode where capacitors are switched to positive reference potential, and discharging mode where capacitors are switched to negative reference potential. This parameter change allows the system to maintain constant common mode voltage by dynamically adjusting the charge state of capacitors based on conversion requirements
2Measurement precision
If capacitors are switched to positive reference potential during conversion phase, then conversion accuracy is improved, but electronic component size must increase to maintain constant common mode voltage
Solution Approach 1:
The patent applies counterweight principle by introducing discharging units that remove charge from input signal lines. When charging units add charge to increase potential, discharging units simultaneously remove charge to counterbalance the effect, thereby maintaining the input common mode voltage constant and preventing the voltage increase that would otherwise occur during conversion phase
Solution Approach 2:
The patent merges the charging and discharging functions into a unified capacitor bank structure where the same capacitors can be selectively switched between charging mode (connected to positive reference potential) and discharging mode (connected to negative reference potential). This integration reduces the need for separate component sets, thereby minimizing electronic component size while maintaining constant common mode voltage
3Measurement precision
If capacitors are switched to positive reference potential during conversion phase, then conversion accuracy is improved, but power consumption increases
Solution Approach 1:
The patent applies counterweight principle by introducing discharging units that remove charge from input signal lines. When charging units add charge to increase potential, discharging units simultaneously remove charge to counterbalance the effect, thereby maintaining the input common mode voltage constant and preventing the voltage increase that would otherwise occur during conversion phase
Solution Approach 2:
The patent employs periodic action by alternately switching capacitors between charging and discharging phases during the conversion process. Rather than continuously maintaining high voltage states, the system periodically toggles capacitor connections between positive and negative reference potentials, achieving the necessary voltage adjustments while minimizing continuous power dissipation
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 reduces or eliminates input common mode voltage variations, allowing for smaller electronic components, reduced power consumption, and improved conversion speed while maintaining optimal common mode conditions.
Implementation Method 1
Each capacitor bank has capacitors of different values... Each capacitor is connected between the signal line and a first reference potential... a voltage level of an input signal applied to the signal lines is stored on each capacitor of the capacitor bank
Implementation Method 2
Each capacitor is connected between the signal line and a first reference potential and is further associated with a switch, so that the respective capacitor can be disconnected from the first reference potential and connected to a second reference potential
Implementation Method 3
a decision latch to receive the input signal line voltage and a logic block which adjusts the switching of the capacitor levels depending on a previous determination in the decision latch
Data Source
AI summary
A differential analog-digital converter is provided. The converter comprises a decision unit for evaluating a potential difference between two input signal lines, a number of charging units for each input signal line each configured to add a predetermined charge onto the respective input signal line, a number of discharging units for each input signal line each configured to remove a predetermined charge from the respective input signal line and a control unit for selectively switching each of the charging units and discharging units so that depending on one result of evaluating the potential difference between the two input signal lines one of the input signal lines is charged by adding the predetermined charge of the respective switched charging unit while the respective other of the input signal lines is discharged by removing the predetermined charge of the respective switched discharging unit.