Sampling Circuit Bias Control for Leakage Current Reduction
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Switched capacitor circuits in sampling circuitry experience significant leakage current due to floating voltages at the input terminals of unused sampling capacitors, leading to erroneous charge transfer and degraded performance, particularly at high gain configurations or high temperatures.
Innovation Solution
Implement bias control circuitry to isolate unused sampling capacitors during the first operational phase by using isolation switches and common coupling switches, ensuring controlled voltage levels and minimizing leakage current.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If switched capacitor circuits are used in sampling circuitry, then the circuit can sample analog voltage and provide sampled values for processing, but leakage current occurs due to floating voltages at input terminals of unused sampling capacitors
Solution Approach 1:
The bias control circuitry proactively sets the input terminals of unused sampling capacitors to a predetermined voltage (common mode voltage) before the sampling operation begins. This preliminary action prevents the floating voltage condition that causes leakage current, ensuring that when switches are opened or closed during sampling, no erroneous charge transfer occurs due to uncontrolled voltage states.
Solution Approach 2:
The bias control circuitry acts as an intermediary between the sampling capacitors and the rest of the circuit. It introduces additional control switches that mediate the connection between the input terminals of sampling capacitors and the common mode voltage terminal, ensuring that unused capacitors are properly biased through this intermediate control layer rather than floating independently.
2Power
If high gain configurations are used in sampling circuitry, then the amplification capability is improved, but leakage current increases leading to erroneous charge transfer
Solution Approach 1:
Before high gain amplification occurs, the bias control circuitry ensures that all sampling capacitors are properly biased to common mode voltage. This preliminary biasing prevents leakage current from developing during the high gain operation, maintaining charge transfer accuracy even when amplification is significant.
Solution Approach 2:
The invention changes the voltage parameter of unused sampling capacitor input terminals from a floating state to a controlled common mode voltage state. This parameter change eliminates the conditions that lead to leakage current, thereby maintaining charge transfer accuracy in high gain configurations where even small leakage currents would cause significant errors.
3Speed
If high temperatures are experienced in sampling circuitry, then operational speed may be maintained, but leakage current increases degrading performance
Solution Approach 1:
The bias control circuitry proactively biases unused sampling capacitors to common mode voltage before temperature-induced leakage becomes problematic. This preliminary action creates a stable voltage reference that resists temperature effects, preventing leakage current from increasing even when operational temperature rises during high-speed operation.
Solution Approach 2:
The invention provides beforehand cushioning by establishing a controlled biasing mechanism that counteracts the effects of temperature increase. By pre-establishing the common mode voltage reference and control switches, the circuit is cushioned against the harmful effects of temperature-induced leakage current before it can degrade performance during high-speed operation.
4Object-generated harmful factors
If bias control circuitry is added to isolate unused sampling capacitors, then leakage current is reduced, but device complexity increases
Solution Approach 1:
The bias control circuitry is designed to be universally applicable to all sampling capacitors in the array. The same control switches and biasing mechanism serve multiple functions: isolating unused capacitors, maintaining common mode voltage reference, and preventing leakage current. This multi-functionality reduces the need for separate dedicated components for each function, thereby limiting the increase in device complexity.
Solution Approach 2:
The invention changes the operational parameter of sampling capacitors from floating voltage to controlled common mode voltage using a systematic approach. By applying the same voltage control parameter uniformly across all capacitors through the bias control circuitry, the solution achieves leakage reduction without requiring complex individualized control for each capacitor, thus limiting complexity increase.
Data Source
AI summary
An example apparatus includes bias control circuitry and sampling circuitry. The example sampling circuitry includes a first switch coupled to a first capacitor in series between an input voltage terminal and a common mode voltage terminal, the first switch including a first terminal coupled to the input voltage terminal. Additionally, the example sampling circuitry includes a second switch coupled to a second capacitor in series between the input voltage terminal and the common mode voltage terminal, the second switch including a first terminal coupled to the input voltage terminal. The example sampling circuitry also includes a third switch including a first terminal, a second terminal, and a control terminal, the first terminal of the third switch coupled to a power supply terminal, the second terminal of the third switch coupled between the first switch and the first capacitor, the control terminal coupled to the bias control circuitry.