Capacitive Level Shifter With Interrupted Feedback for Safe Voltage Swing
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Solution Overview
Problem
Existing level shifters often fail to maintain a consistent voltage swing for both input and output signals, which can damage core devices with thinner gate dielectric layers, and do not effectively increase the logically low voltage level, leading to reliability concerns and increased device size.
Innovation Solution
A level shifting apparatus comprising an inverter, a capacitor, and an edge detector that selectively interrupts feedback to maintain a constant voltage swing, using capacitors with specific capacitance values to prevent direct current connection and reduce voltage swing, allowing operation with devices having thin gate dielectric layers and enabling frequency-independent signal propagation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If level shifters use I/O devices with thicker gate dielectric layers to withstand higher voltages, then voltage swing range increases, but device size increases
Solution Approach 1:
The patent applies local quality by using I/O devices with thicker gate dielectric layers specifically in the level shifter circuit where high voltage swing is required, while core devices with thinner gate dielectric layers are used elsewhere where smaller size is critical. This localized application allows the level shifter to handle higher voltages without unnecessarily increasing the size of the entire system.
2Speed
If level shifters increase voltage level of logically high voltage but maintain same logically low voltage level, then output voltage swing increases, but core devices with thinner gate dielectric may be damaged
Solution Approach 1:
The patent implements feedback by continuously monitoring the output voltage level and adjusting the bias voltage accordingly. The bias circuit receives feedback about the output voltage and dynamically adjusts the bias to ensure that the logically low voltage level is elevated sufficiently to prevent damage to core devices, while still maintaining the desired voltage swing for logically high voltages.
Solution Approach 2:
The patent changes parameters by dynamically adjusting the bias voltage level based on operating conditions. The bias circuit modifies the voltage parameters in real-time to maintain safe operating margins for core devices while optimizing the voltage swing characteristics. This parameter adjustment ensures that the logically low voltage is always at a safe level above what core devices can tolerate.
3Reliability
If level shifters include bias circuit to increase logically low voltage level, then device reliability improves, but device complexity increases
Solution Approach 1:
The patent merges the bias circuit functionality with the existing level shifter structure. The bias circuit is integrated into the level shifter design, sharing common transistors and interconnect structures with the main signal path. This merging approach allows the bias circuit to provide reliability enhancement without adding completely separate components, thereby reducing the overall complexity increase compared to a fully independent bias circuit implementation.
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 maintains a consistent voltage swing for both input and output signals, reduces device size, and increases switching speed, while preventing voltage swing-related damage to core devices, allowing operation up to 10 Gb/s without signal attenuation.
Implementation Method 1
A first capacitor is coupled between a first voltage node and a second voltage node. The first capacitor prevents a direct current (DC) connection between the first inverter and the second inverter.
Implementation Method 2
An edge detector is configured to detect an edge in the first voltage corresponding to a first current from the first voltage node to the second voltage node.
Data Source
AI summary
A level shifting apparatus includes a first inverter configured to receive an input signal and a second inverter capacitively coupled with an output of the first inverter, the second inverter being configured to output an output signal. A transmission gate is configured to feed back the output signal to an input of the second inverter, wherein the transmission gate is configured to selectively interrupt feedback of the output signal to the input of the second inverter.