Capacitive Level Shifter Circuit for Continuous Voltage Domain Shifting
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Solution Overview
Problem
Existing level shifter circuits face challenges in achieving continuous mode operation and efficient voltage domain changes, particularly when using low-voltage devices and capacitive shifting methods.
Innovation Solution
The implementation of a capacitive level shifter circuit with a cascoded configuration, utilizing low-voltage MOS components and capacitor refresh circuitry to facilitate continuous operation and fast voltage propagation without crossbar current.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If capacitor-based level shifting is used to achieve fast voltage propagation, then speed is improved, but the circuit cannot operate in continuous mode due to lack of refresh mechanism
Solution Approach 1:
The patent implements periodic refresh action through clocked transistors that periodically recharge the capacitors maintaining the voltage shift. This periodic refreshing enables continuous operation mode while preserving the fast voltage propagation benefits of capacitor-based level shifting.
Solution Approach 2:
The patent applies preliminary action by pre-charging the capacitors through dedicated refresh circuitry before they are needed for signal transmission. This ensures the voltage shift is already established and ready for immediate signal propagation, enabling both fast switching and continuous operation.
2Speed
If boosted clock is used for voltage shifting in cascoded buffers, then speed is improved, but the approach cannot be applied in continuous mode
Solution Approach 1:
The patent makes the circuit dynamic by using clocked transistors that are activated periodically to refresh the capacitors. This dynamic refresh mechanism allows the circuit to adapt to continuous operation requirements while maintaining the fast voltage shifting performance achieved through boosted clock techniques.
Solution Approach 2:
The patent ensures continuity of useful action by implementing a refresh mechanism that continuously maintains the voltage shift on the capacitors. This continuous refreshing action eliminates the limitation of previous approaches that could only operate in discrete modes, enabling true continuous mode operation.
3Area of stationary object
If low-voltage MOS devices are used up to twice their maximum voltage range, then area is reduced, but voltage range extension becomes difficult
Solution Approach 1:
The patent introduces capacitors as intermediary elements that store and transfer voltage shifts between different voltage domains. This intermediary approach allows low-voltage MOS devices to operate in higher voltage ranges by using the capacitors to bridge the voltage difference, thus reducing area while extending voltage range capability.
Solution Approach 2:
The patent changes the operating parameters by using capacitive coupling to shift voltage levels dynamically. This allows low-voltage devices to effectively operate at higher voltage ranges by superimposing AC voltage shifts on DC bias points, thereby extending the usable voltage range without increasing device area.
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
This approach enables efficient voltage domain changes and fast propagation of shifted voltages, while maintaining low power consumption and area occupancy, thus supporting continuous mode operation in level shifter circuits.
Implementation Method 1
a first shift capacitor coupled to the first drive node and a second shift capacitor coupled to the second drive node
Implementation Method 2
a first refresh transistor having a control terminal as well as a first refresh current flow path therethrough between a supply node and the first shift capacitor via the first drive node, the first refresh current flow path configured to become conductive in response to a first refresh signal applied to the control terminal of the first refresh transistor
Data Source
AI summary
A level-shifter circuit receives one or more input signals in an input level domain and includes provides at an output node an output signal in an output level domain shifted with respect to the input level domain. The circuit includes output circuitry including a first drive node and a second drive node that receive first and second logical signals so that the output signal has a first output level or a second output level in the output level domain as a function of at least one of the first and second logical signals. The circuit includes first and second shift capacitors coupled to the first and second drive nodes as well as capacitor refresh circuitry.