Bootstrap Sampling Switch Circuit Power Reduction
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Solution Overview
Problem
Existing bootstrap circuits for switched capacitor sampling in analog to digital converters (ADCs) consume high power due to the need to repeatedly charge the bootstrap capacitor and gate capacitance, leading to non-linear effects and increased power dissipation, which affects the performance and efficiency of the ADCs in applications like medical imaging and security systems.
Innovation Solution
A novel bootstrap circuit design that charges the bootstrap capacitor only once per conversion cycle and uses a three-phase control signal scheme to maintain a constant gate-to-source voltage for the sampling transistor, reducing the load on the driver amplifier and minimizing power consumption while ensuring linear performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the bootstrap capacitor is repeatedly charged during each sampling operation, then the sampling switch can be turned on rapidly, but power consumption increases significantly
Solution Approach 1:
The bootstrap capacitor is charged in advance during a dedicated precharge phase before the sampling operation begins. This preliminary charging action ensures that when the sampling switch needs to turn on, the capacitor is already charged and can immediately provide the necessary gate voltage boost without requiring repeated charging during the sampling cycle, thus reducing power consumption while maintaining fast switch turn-on speed.
2Reliability
If the driver amplifier drives the bootstrap capacitor and sampling switch gate capacitance repeatedly, then the sampling switch operates correctly, but non-linear effects increase
Solution Approach 1:
The operation is divided into distinct phases: a precharge phase where the bootstrap capacitor is charged, and a sampling phase where the capacitor is not driven. This segmentation separates the charging action from the sampling action, ensuring that during the critical sampling phase, the driver amplifier does not repeatedly charge the capacitor, thereby reducing non-linear effects and improving linearity while maintaining correct switch operation through proper phase timing.
3Productivity
If the sampling switch is turned on rapidly using a bootstrap circuit, then sampling efficiency improves, but power dissipation increases
Solution Approach 1:
The bootstrap capacitor charging is performed periodically at specific intervals (during precharge phases) rather than continuously or with every sampling operation. This periodic action maintains the necessary voltage boost for efficient sampling switch operation while minimizing the frequency of charging events, thereby reducing overall power dissipation while preserving sampling efficiency.
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
The solution significantly reduces power consumption by approximately 20% and maintains high linearity in ADCs, improving the overall performance and efficiency of the analog to digital conversion process, particularly in applications requiring precise signal processing like medical imaging and security systems.
Implementation Method 1
a bootstrap capacitor having a top plate coupled to the gate terminal of the MOS transistor
Data Source
AI summary
A bootstrap circuit for a sampling transistor. A circuit includes a MOS transistor having a source terminal coupled to an input for receiving an input voltage; an output at a drain terminal of the MOS transistor coupled to one plate of a sampling capacitor; a first switch coupling the input voltage to a gate terminal of the MOS transistor responsive to an initial phase control signal; a bootstrap capacitor having a top plate coupled to the gate terminal of the MOS transistor and coupled to the first switch; a second switch coupling a bottom plate of the bootstrap capacitor to a first low voltage supply responsive to the initial phase control signal; a third switch coupling the bottom plate of the bootstrap capacitor to a positive voltage supply greater than the first low voltage supply responsive to a first phase periodic control signal. Additional circuits and systems are disclosed.