Radiation-Hardened Level Shifter Without Direction Control
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Solution Overview
Problem
Current level shifter circuits lack cold spare tolerance, radiation hardening, and compatibility with both push-pull and open drain signal types, and require external direction control inputs, limiting their use in high-radiation environments and frequency operation.
Innovation Solution
A novel level shifter circuit design that is cold spare tolerant and radiation hardened, eliminating the need for external direction control inputs, supporting both push-pull and open drain signaling, and operating at frequencies above 2 MHz, using a topology with NMOS pass-gates, pull-up resistors, and one-shot circuits for auto-sensing and improved signal transition times.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If external direction control inputs are used to swap between bi-directional configurations, then the level shifter can function bidirectionally, but the system design becomes more complex and costs increase
Solution Approach 1:
The level shifter circuit automatically detects the signal direction and configures itself without requiring external direction control inputs. The circuit monitors the voltage levels at its terminals and autonomously determines whether to operate in forward or reverse mode, eliminating the need for additional control circuitry while maintaining full bidirectional functionality
Solution Approach 2:
The circuit dynamically adapts its configuration based on real-time voltage level detection. Transistors are automatically switched between different operational states depending on which terminal is at a higher voltage potential, enabling the circuit to flexibly change its signal path direction without external control
2Reliability
If the level shifter is designed for radiation hardened environments with cold spare tolerance, then reliability in high-radiation environments improves, but device complexity increases
Solution Approach 1:
The level shifter circuit incorporates cold spare tolerance by pre-configuring redundant transistor pairs that can automatically take over if radiation causes failure in the active transistors. This fail-safe mechanism is built into the basic circuit topology, providing radiation hardening without requiring complex external redundancy management systems
Solution Approach 2:
The circuit uses universal transistor pairs that can serve dual purposes: active signal transmission during normal operation and standby replacement in case of radiation-induced failure. This multi-functional design allows the same circuit elements to provide both operational and backup functions, reducing overall complexity compared to separate active and standby circuits
3Adaptability or versatility
If the level shifter supports both push-pull and open drain signaling, then compatibility with various IC interfaces improves, but circuit design becomes more complex
Solution Approach 1:
The level shifter automatically detects whether it is connected to a push-pull or open drain output by monitoring the voltage levels and current flow characteristics. Based on this detection, the circuit self-configures its internal transistor states to provide appropriate level shifting for the detected signal type, eliminating the need for external configuration controls
Solution Approach 2:
The circuit dynamically adjusts its output impedance and transistor switching behavior based on the detected signal type. For push-pull inputs, the circuit operates in one mode, while for open drain inputs, it automatically transitions to a different operational mode with appropriate impedance matching, providing seamless adaptation without complex control logic
4Speed
If the level shifter operates at higher frequencies above 2 MHz, then frequency handling capability improves, but signal transition time control becomes more difficult
Solution Approach 1:
The level shifter uses synchronized transistor switching that operates in periodic cycles matched to the input signal frequency. This periodic switching ensures that transistors are turned on and off at optimal moments in each signal cycle, minimizing transition time and maximizing frequency handling capability up to and beyond 2 MHz
Solution Approach 2:
The circuit performs preliminary voltage level preparation by pre-charging or pre-discharging capacitor nodes before the actual signal transition occurs. This preliminary action reduces the time required for voltage levels to stabilize during high-frequency operation, enabling faster signal transition times at frequencies above 2 MHz
Data Source
AI summary
A level shifting circuit, the circuit comprising a VL input; an I/O VL; a VCC input; an I/O VCC; a first pull-up resistor disposed between the VL input and I/O VL; a second pull-up resistor disposed between the VCC input and I/O VCC; a first pull-up assist circuit comprising a first pull-up assist p-channel MOSFET having a source/body, drain, and gate, the source/body and drain being connected to VL and I/O VL; a second pull-up assist circuit comprising a second pull-up assist p-channel MOSFET having a source/body, drain, and gate, the source/body and drain being connected to VCC and I/O VCC, respectively; a pass-gate n-channel MOSFET in operative communication with I/O VL, I/O VCC, and VL, the pass-gate being configured to reduce the voltage level of a signal driven from I/O VCC to the voltage level of I/O VL; and a one-shot circuit configured to detect a I/O VL or I/O VCC transition from a low state to a high state, to produce a pulse in response thereto, and to communicate that pulse to the gates of the first and second pull-up assist p-channel MOSFETs, wherein the second pull-up resistor is configured to increase the voltage level of a signal driven from I/O VL to the voltage level of I/O VCC.