Voltage Generator Biasing Using Capacitive Coupling
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Solution Overview
Problem
Conventional high bias voltage generators for MEMS microphones require expensive high-voltage technologies, such as CMOS Flash or DeMOS, which increase production costs and are not suitable for standard CMOS processes, limiting the use of standard CMOS devices in voltage generator designs.
Innovation Solution
The implementation of a capacitive coupling scheme to bypass the output ripple filter in the high voltage domain, allowing the use of standard CMOS technology by steering the control node of a bypass switch using a coupling capacitor, eliminating the need for high-voltage devices and enabling the design of high bias voltage generators with standard CMOS components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If high-voltage technologies (CMOS Flash or DeMOS) are used in voltage generator design, then the ability to handle high voltages (>5V) is improved, but production costs increase and device complexity increases
Solution Approach 1:
The voltage generator is divided into two distinct domains: a high-voltage domain for voltage generation and a low-voltage domain for control logic. This segmentation allows each domain to use appropriately optimized technology - high-voltage transistors for power handling and standard CMOS for cost-effective control, resolving the contradiction between high-voltage capability and manufacturing cost
Solution Approach 2:
A level shifter circuit acts as an intermediary between the high-voltage and low-voltage domains. This mediator translates control signals from the low-voltage standard CMOS domain to the high-voltage domain, enabling standard CMOS devices to control high-voltage operations without requiring expensive high-voltage technology throughout the entire system
2Reliability
If high-voltage technologies are used in voltage generator, then high voltage handling capability is improved, but the number of processing steps and layers increases
Solution Approach 1:
The device structure is segmented into high-voltage and low-voltage regions with different processing requirements. The high-voltage transistors use fewer processing steps and thinner gate oxides compared to standard CMOS, while the control logic uses standard CMOS processing. This segmentation reduces the overall device complexity by not requiring the entire device to undergo the more complex standard CMOS high-voltage processing steps
Solution Approach 2:
Different regions of the device are given different local qualities - the high-voltage transistors have thinner gate oxides optimized for high-voltage operation with simpler processing, while the control logic region has thicker gate oxides for standard CMOS compatibility. This local differentiation allows each region to be optimized for its specific function without requiring the entire device to have the more complex standard CMOS high-voltage structure
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 production costs by eliminating the need for high-voltage technologies, allowing for the use of standard CMOS devices in high bias voltage generators, while maintaining efficient voltage regulation and reducing startup times for MEMS microphones.
Implementation Method 1
A coupling capacitor comprising a first plate and a second plate is provided. The first plate is coupled to a control node of the bypass switch. A bypass control signal is received. The control node of the bypass switch is toggled between a first voltage to a second voltage different from the first voltage by toggling the second plate of the coupling capacitor based on the bypass control signal.
Data Source
AI summary
In accordance with an embodiment of the present invention, a method of operating a voltage generator includes providing a bypass switch to bypass a ripple filter coupled to a power converter. A coupling capacitor includes a first plate and a second plate. The first plate is coupled to a control node of the bypass switch. A bypass control signal is received. The control node of the bypass switch is toggled between a first voltage to a second voltage different from the first voltage by toggling the second plate of the coupling capacitor based on the bypass control signal.