Analog Switch Gate Control for High-Voltage Signal Transmission
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Solution Overview
Problem
Analog switch circuits face challenges in handling high input voltages beyond the breakdown voltage of NMOS and PMOS transistors, leading to increased costs and reduced transistor integration in high breakdown voltage processes.
Innovation Solution
The proposed analog switch circuit includes a controller with a voltage generating circuit that generates high-side and low-side voltages based on the input voltage and supply voltages, allowing for control of the gates and back gates of NMOS and PMOS transistors to manage voltages within safe limits, enabling switching beyond the breakdown voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If high breakdown voltage elements are used to handle high input voltages, then the analog switch can transmit higher voltages, but the manufacturing cost increases and transistor integration degree lowers
Solution Approach 1:
The patent introduces a voltage dividing circuit as an intermediary between the high-voltage input signal and the gate terminals of the transistors. This voltage dividing circuit divides the input signal into multiple voltage levels, allowing the transistors to operate within their safe breakdown voltage limits while still handling high-voltage signals. This resolves the contradiction by enabling high-voltage transmission without requiring expensive high-breakdown-voltage transistors.
2Reliability
If high breakdown voltage elements are used to handle high input voltages, then the analog switch can transmit higher voltages, but the transistor integration degree lowers
Solution Approach 1:
The voltage dividing circuit acts as a mediator that protects the transistor integration structure from high-voltage damage. By dividing the input voltage before it reaches the transistor gates, the circuit allows standard low-breakdown-voltage transistors to be used, maintaining high integration density while still enabling the overall circuit to handle high-voltage signals through the intermediary voltage division mechanism.
3Ease of operation
If the gate voltage follows the input voltage directly, then the switching control is simple, but the voltage exceeds the breakdown voltage of the transistor
Solution Approach 1:
The voltage dividing circuit serves as an intermediary that transforms the input voltage into safe gate control voltages. This maintains the simplicity of switching control through the control signal while preventing the gate voltage from exceeding transistor breakdown limits. The intermediary circuit automatically performs the voltage transformation without complicating the switching operation.
Data Source
AI summary
Provided is an analog switch circuit that allows switching between an on-state and an off-state according to a control signal, the analog switch circuit including a main input terminal that receives an input voltage, an output terminal, an upper-side power supply terminal that receives an upper supply voltage, a lower-side power supply terminal that receives a lower supply voltage, a main N-channel MOS transistor and a main P-channel MOS transistor that are disposed in parallel between the main input terminal and the output terminal, and a controller that includes a voltage generating circuit that generates a high-side voltage according to the upper supply voltage and the input voltage and a low-side voltage according to the input voltage and the lower supply voltage. The controller can control a gate and a back gate of each of the main N-channel and P-channel MOS transistors based on the high-side and low-side voltages.