CMOS Bus Driver Circuit for High-Voltage Radiation-Tolerant Operation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional low-voltage CMOS processes are not radiation-tolerant and cannot handle the high voltage levels required for CAN bus communication, limiting the implementation of radiation-hard driver circuits for bi-directional communication buses like CAN.
Innovation Solution
A bi-state driver circuit design that includes a series of transistors and voltage divider circuits, allowing transistors to operate within safe voltage ranges even under high external voltages, implemented in a low-voltage CMOS process, enabling radiation-tolerant tri-state driver circuits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional low-voltage CMOS processes are used, then manufacturing cost and integration density are improved, but radiation tolerance and voltage handling capability deteriorate
Solution Approach 1:
The transistor gate is segmented into two independent gates (first gate and second gate), allowing separate control of channel formation and voltage stress protection. This segmentation enables the transistor to function in both low-voltage operation mode and high-voltage/radiation tolerant mode using the same physical structure fabricated in standard CMOS process.
Solution Approach 2:
A voltage divider circuit is introduced as an intermediary between the output terminal and the control terminal of the second transistor. This voltage divider scales down the high voltage signals from the output terminal to safe levels that can be handled by the low-voltage CMOS transistors, enabling the system to interface with high-voltage buses while protecting the sensitive transistor gates.
2Object-affected harmful factors
If high voltage transistors and protection diodes are used, then voltage handling capability is improved, but device complexity and manufacturing cost increase
Solution Approach 1:
The dual-gate transistor structure serves multiple functions simultaneously: it acts as a voltage-controlled switch for normal operation, provides inherent protection against voltage spikes through the second gate control, and enables radiation tolerance through the controlled channel formation. This eliminates the need for separate protection diodes and complex voltage clamping circuits required in conventional designs.
Solution Approach 2:
The invention changes the control parameter from single-gate voltage control to dual-gate independent control. By controlling the second gate with a scaled-down version of the output voltage through the voltage divider, the transistor operating parameters (threshold voltage, channel conductivity) are dynamically adjusted to match the instantaneous output voltage level, providing adaptive protection without additional components.
3Object-affected harmful factors
If high voltage CMOS processes are used, then voltage handling capability is improved, but radiation tolerance deteriorates
Solution Approach 1:
The invention changes the control parameter from single-gate voltage control to dual-gate independent control. By controlling the second gate with a scaled-down version of the output voltage through the voltage divider, the transistor operating parameters (threshold voltage, channel conductivity) are dynamically adjusted to match the instantaneous output voltage level, providing adaptive protection without additional components.
4Object-affected harmful factors
If voltage divider circuits are added, then voltage protection is improved, but device complexity increases
Solution Approach 1:
The voltage divider circuit is merged with the transistor gate control structure, where the divided voltage directly controls the second gate. This integration eliminates the need for separate protection circuits and allows the voltage scaling function to be performed within the existing transistor control path, minimizing additional complexity.
Data Source
Figure 1
Figure 2
Figure 3
AI summary
This application relates to a bi-state driver circuit (100) for switching an output terminal (60) between a first predetermined voltage level (VSS) and a high impedance state. The bi-state driver circuit (100) comprises a first string of transistors (10) connected between the output terminal (60) and the first predetermined voltage level (VSS) and comprising at least a first transistor (11-1) arranged closer to the first predetermined voltage level (VSS) and a second transistor (11-2) arranged closer to the output terminal (60), a voltage divider circuit (50) connected between the output terminal (60) and a voltage level of a control signal (TX) attaining voltage levels between the first predetermined voltage level and a second predetermined voltage level, comprising at least one intermediate node having an intermediate voltage level between a voltage level of the output terminal and the voltage level of the control signal, and a second string of transistors (20-1) connected between the intermediate node (51-1) of the voltage divider circuit (50) and the second predetermined voltage level (VDD), and comprising at least a third transistor (21-1-1). A control terminal of the second transistor (21-1-1) is connected to the intermediate node (51-1). The first transistor (11-1) is configured to be switched in accordance with the control signal (TX). The third transistor is configured to be switched in accordance with the control signal, in a phase-locked relationship with the first transistor. The application further relates to a driver circuit for switching a first output terminal between a first output voltage level and a high impedance state, and for switching a second output terminal between a second output voltage level and the high impedance state. The application yet further relates to a method of controlling a bi-state driver circuit.