Bulk-Controlled Switch Circuit for Fast Low-Leakage Voltage Selection
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Solution Overview
Problem
Conventional bulk switching transistor circuits face issues with parasitic coupling leading to unintended power leakage and latch-up due to variable source and drain voltages, which necessitate faster and more accurate switching to mitigate these adverse effects.
Innovation Solution
The implementation of a bulk-controlled switch circuit with parallel transistors, current mirror circuits, and impedance circuits that dynamically switch between source and drain voltages, along with constant current generators to introduce hysteresis and improve control, ensuring accurate voltage domain preference and reducing parasitic diode coupling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If conventional bulk switching circuitry is used with variable source and drain voltages, then the circuit can operate with floating voltages, but parasitic coupling causes unintended power leakage and latch-up
Solution Approach 1:
The patent introduces an intermediary bulk voltage control mechanism that mediates between the source and drain voltages. By controlling the bulk voltage to follow the higher of the two voltages through controlled coupling, the patent prevents direct parasitic coupling between source and drain, thereby eliminating unintended power leakage while maintaining floating voltage operation capability
Solution Approach 2:
The patent implements a feedback mechanism where the bulk voltage is dynamically adjusted based on the relative levels of source and drain voltages. The bulk voltage control circuit continuously monitors and responds to voltage differences, creating a feedback loop that maintains proper voltage relationships and prevents latch-up conditions while preserving adaptability to floating voltage scenarios
2Speed
If the switching transistor transconductance is increased to speed up switching, then switching speed improves, but parasitic coupling effects become more pronounced
Solution Approach 1:
The patent converts the potentially harmful parasitic coupling effects into a beneficial mechanism by intentionally utilizing the parasitic diode coupling to achieve controlled bulk voltage follow-up. Instead of trying to eliminate all parasitic effects, the patent harnesses them to create the desired bulk voltage tracking behavior, thereby maintaining fast switching while preventing harmful leakage through clever use of the parasitic effects
3Device complexity
If simple bulk switching is implemented, then device complexity is reduced, but leakage control and switching accuracy deteriorate
Solution Approach 1:
The patent segments the bulk voltage control function into distinct operational modes: a high-impedance state for normal operation and a controlled coupling state for leakage prevention. By dividing the control mechanism into these segments that can be selectively activated, the patent achieves improved leakage control without requiring complete redesign of the entire circuit, thus maintaining reasonable complexity while enhancing reliability
Data Source
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AI summary
According to an aspect, there is provided an apparatus comprising: a bulk-controlled switch circuit comprising a first transistor coupled to a load and having a source coupled to a source voltage and a drain coupled to a drain voltage, a second transistor and a third transistor coupled, in parallel with the first transistor, to one another in series between the source voltage and the drain voltage, wherein a bulk of the first transistor is coupled with bulks of the second transistor and the third transistor, wherein a gate of the second transistor is coupled to the source voltage via a first impedance circuit and a gate of the third transistor is coupled to the drain voltage via a second impedance circuit to form a comparator switch controlled by the source voltage and the drain voltage and to dynamically switch a greater one of the source voltage and the drain voltage to the load; a first current generator circuit and a second current generator circuit; a first current mirror circuit biased by the first current generator circuit, responsive to the source voltage, and configured to trigger the second transistor to couple the source voltage to the load when the source voltage is above the drain voltage; a second current mirror circuit biased by the second current generator circuit, responsive to the drain voltage, and configured to trigger the third transistor to couple the drain voltage to the load when the drain voltage is above the source voltage.