Level Shifter Circuit with Separate Switching and Holding Currents
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Solution Overview
Problem
Conventional high-speed level shifters consume high power to maintain a constant logic level when operating between systems with multiple pairs of non-shared voltage rails, making it difficult to achieve efficient level shifting between circuits with different logic voltage domains.
Innovation Solution
A novel level shifting circuit with a switching current generator and a holding current generator, where the holding current is produced independently of the switching current, allowing for separate selection of switching speed and quiescent power, and utilizing differential current sensors and current mirrors to manage voltage levels across different voltage rails.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If a conventional high-speed level shifter is used to maintain constant logic level between circuits with non-shared voltage rails, then the logic level stability is improved, but the power consumption increases significantly
Solution Approach 1:
The level shifter is segmented into two independent functional blocks: a switching current generator for high-speed transitions and a holding current generator for maintaining logic levels. This segmentation allows each block to be optimized independently, with the holding current operating at minimal power levels while the switching current provides fast transitions only when needed.
Solution Approach 2:
The holding current generator uses periodic feedback control to maintain logic levels, adjusting the holding current only when voltage level shifts are detected. This periodic action replaces continuous high-power consumption with intermittent low-power adjustments, significantly reducing overall power usage while maintaining stability.
2Device complexity
If the holding current and switching current are combined in a single generator, then the device complexity is reduced, but the ability to independently optimize switching speed and power consumption is lost
Solution Approach 1:
The current generation function is divided into two separate generators: one dedicated to switching operations and another to holding operations. This segmentation enables independent optimization of switching speed (controlled by switching current parameters) and power consumption (controlled by holding current parameters), while the modular design minimizes the increase in overall circuit complexity.
3Adaptability or versatility
If voltage levels of one pair of voltage rails move with respect to another pair, then the adaptability to different voltage domains is improved, but the logic level stability at the output may change
Solution Approach 1:
The holding current generator acts as an intermediary that compensates for voltage level shifts between non-shared rails. By detecting changes in the voltage relationship between rail pairs and adjusting the holding current accordingly, it maintains stable logic levels at the output despite variations in the input voltage domains, enabling adaptable operation across different voltage configurations.
Data Source
AI summary
A level shifting circuit and methodology involving a switching current generator responsive to switching of an input signal for producing a switching current to switch an output signal, and a holding current generator for producing a holding current to hold the logic level of the output signal in accordance with the logic level of the input signal. The holding current is produced independently of the switching current.