Bootstrap Digital Buffer for Low-Voltage High-Threshold MOS Drive
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Solution Overview
Problem
Existing ICs with MOS circuits face inefficiencies due to high standby power consumption and inability to operate at lower voltages, particularly when dealing with high-threshold voltage requirements, leading to inefficiency and leakage issues.
Innovation Solution
A circuit design that includes a first inverter connected to a high-threshold MOS device, with diodes and capacitors configured to enable operation below the threshold voltage, utilizing low-threshold MOS devices to reduce leakage and allow efficient operation with single supply low-dropout regulators.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a high-threshold MOS device is used, then the circuit can operate at higher voltages with better noise immunity, but the circuit cannot operate at lower voltages and consumes more standby power
Solution Approach 1:
The bootstrap capacitor is pre-charged to a voltage higher than the supply voltage before the MOS device needs to operate. This preliminary charging action stores energy that can be transferred to the gate terminal when needed, enabling the device to operate below its threshold voltage without requiring continuous high voltage supply, thus reducing standby power consumption while maintaining noise immunity.
Solution Approach 2:
The bootstrap capacitor acts as an intermediary energy storage element between the supply voltage and the MOS device gate. It temporarily holds and transfers voltage energy, allowing the gate to reach the required threshold voltage even when the supply voltage is lower than the device's normal operating threshold. This mediator enables low-voltage operation while preserving the high-threshold device's noise immunity characteristics.
2Reliability
If the threshold voltage of the MOS device is increased, then the noise immunity is improved, but the standby power consumption increases due to threshold drop effects
Solution Approach 1:
The bootstrap capacitor is pre-charged to a voltage higher than the supply voltage before the MOS device needs to operate. This preliminary charging action stores energy that can be transferred to the gate terminal when needed, enabling the device to operate below its threshold voltage without requiring continuous high voltage supply, thus reducing standby power consumption while maintaining noise immunity.
Solution Approach 2:
The invention dynamically changes the gate voltage parameter by using the bootstrap capacitor to boost the gate voltage above the supply voltage during operation, and allowing it to discharge during standby periods. This parameter change enables the high-threshold device to operate efficiently at lower voltages, reducing the threshold drop effects and associated standby power losses while preserving noise immunity when needed.
3Reliability
If existing bootstrap circuits are used to raise the gate potential, then the threshold drop effects are reduced, but the circuit complexity increases and standby power consumption increases
Solution Approach 1:
The bootstrap capacitor serves multiple functions: it acts as an energy storage element for voltage boosting, a timing element for controlling the operation cycles, and a filter for stabilizing the gate voltage. By making this single component multi-functional, the invention reduces the need for additional circuit elements, thereby lowering overall circuit complexity while maintaining threshold voltage stability and reducing standby power consumption.
Solution Approach 2:
The bootstrap capacitor automatically charges and discharges based on the operational state of the MOS device without requiring external control circuitry. During the off-state, it discharges to maintain the gate voltage; during the on-state, it charges to provide the necessary voltage boost. This self-service behavior eliminates the need for complex control logic and additional active components, simplifying the overall circuit while maintaining reliable threshold voltage stability.
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
Enables high-threshold MOS devices to operate at lower voltages with reduced leakage current and efficient power usage, effectively addressing inefficiencies in existing designs by using a low-threshold MOS inverter and charging/discharging capacitors to maintain circuit functionality.
Implementation Method 1
charging and discharging of a first capacitor and a second capacitor in the circuit enables the high threshold MOS device to operate on a low supply voltage line
Data Source
AI summary
The present invention is a method and circuitry for driving a high-threshold MOS device on low input voltages. The invention includes a circuit that operates on a supply voltage that is less than the threshold voltage of the high-threshold MOS device. The circuit includes one or more low threshold MOS inverters and one or more capacitors that operate at low input voltages. The one or more low threshold MOS inverters operate in a manner that the one or more capacitors get charged to a voltage greater than the low input voltage. Thereafter, the charged capacitor drives the high threshold MOS device.