Capacitive Voltage Level Shifter for EOS-Safe Multi-Domain Output
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Solution Overview
Problem
Existing voltage level shifters suffer from electrical overstress (EOS) and time-dependent dielectric breakdown (TDDB) issues, particularly due to the lack of effective voltage shifting for low logical values and the need for additional bias circuits, which are not favored.
Innovation Solution
A voltage level shifter design that uses core transistors and input-output (IO) transistors with thicker gate oxides, incorporating a protection circuit to manage voltage drops and prevent electrical breakdown, and a capacitive coupling mechanism to generate output voltages across multiple domains without static currents.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If existing voltage level shifters are used to shift voltage levels, then voltage level shifting is achieved, but transistors suffer from electrical overstress and time dependent dielectric breakdown
Solution Approach 1:
A protection circuit is introduced as an intermediary between the high voltage domain and low voltage domain transistors. This protection circuit includes transistors that act as mediators to control voltage drops across critical transistors, preventing electrical overstress and dielectric breakdown while allowing voltage level shifting to occur.
Solution Approach 2:
The invention changes the voltage parameters dynamically by using control signals to adjust the voltage drops across protection transistors. By varying the voltage parameters in real-time based on input signal levels, the circuit maintains transistor safety margins while achieving the required voltage level shifting functionality.
2Reliability
If a bias circuit is added to provide constant bias to prevent EOS and TDDB, then transistor protection is improved, but device complexity increases
Solution Approach 1:
The protection circuit is designed to be self-regulating, using the input signal itself to control the voltage drops across protection transistors. The circuit automatically adjusts its protection level based on the operating conditions without requiring external bias circuits, thereby maintaining reliability while minimizing added complexity.
Solution Approach 2:
The protection circuit transistors serve multiple functions: they protect against electrical overstress, prevent dielectric breakdown, and simultaneously enable voltage level shifting. This multi-functionality reduces the need for separate bias circuits and other protective components, keeping the overall device complexity low.
3Device complexity
If voltage level shifting is implemented without proper protection, then device complexity is reduced, but harmful factors such as EOS and TDDB increase
Solution Approach 1:
The protection circuit acts as an intermediary layer that adds minimal complexity while effectively blocking harmful voltage spikes. The intermediary transistors are strategically placed to protect critical nodes without requiring complex control logic or additional circuitry, achieving a good balance between simplicity and protection.
4Device complexity
If existing level shifters shift only high logical value voltage levels, then circuit design is simplified, but low logical value voltage levels are not shifted
Solution Approach 1:
The protection circuit is designed to handle both high logical value and low logical value voltage levels simultaneously. By using control signals that respond to both voltage levels, the circuit achieves universal voltage level shifting capability while maintaining relatively simple circuit design through shared protection transistors and control logic.
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
The solution effectively shifts voltage levels across multiple domains while protecting transistors from electrical breakdown, reducing the risk of EOS and TDDB, and eliminating the need for static currents, thus improving the reliability and efficiency of the voltage level shifting process.
Implementation Method 1
a capacitive coupling mechanism to generate output voltages across multiple domains
Data Source
AI summary
A circuit includes a first capacitive device and a first latch. The first capacitive device includes a first end configured to receive a first input signal and a second end coupled with the first latch. The first latch includes a first transistor and a second transistor that are of a first type. A first terminal of the first transistor and a first terminal of the second transistor are each configured to receive a first voltage value. A second terminal of the first transistor is coupled with a third terminal of the second transistor. A third terminal of the first transistor is coupled with a second terminal of the second transistor and with the second end of the capacitive device, and is configured to provide an output voltage for the first latch.