Level Shifter Circuit to Break Word-Line Fighting Paths
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Solution Overview
Problem
Conventional level shifters in non-volatile memory devices experience failures in word-line selection and de-selection due to a 'fighting path' between transistors, leading to inefficient voltage operation and read speed loss, and increasing transistor length to resolve this issue contradicts the design goal of compactness.
Innovation Solution
A level shifter design that includes a first and second level-switching device with switch devices and control switches to weaken the current path between input and operational voltages, allowing for proper output voltage selection and de-selection, thereby breaking the fighting path and improving voltage operation range and read speed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the resistance of transistor N2 (or P2) is increased to completely turn on transistor N1 (or P1) for proper voltage output, then the word-line de-selection (or selection) reliability is improved, but the transistor length increases which enlarges the X-decoder size
Solution Approach 1:
A control transistor (N21 or P21) is introduced as an intermediary component to regulate the current path between the input voltage and the operational voltage. This control transistor acts as a mediator that can completely turn on the output transistor (N1 or P1) without requiring an increase in the length of transistor N2 (or P2), thus resolving the contradiction between reliability and transistor length.
Solution Approach 2:
The current path is segmented into multiple controlled segments by introducing the control transistor. Instead of relying on a single transistor (N2 or P2) to provide both current regulation and complete turn-on capability, the function is divided between the control transistor and the output transistor, allowing each to be optimized independently.
2Reliability
If the voltage Vp is lowered from high voltage (6V) to Vcc level (2.5V) to avoid fighting path issues, then the select/de-select problems are avoided, but the read speed is reduced
Solution Approach 1:
The circuit dynamically controls the current path using the control transistor based on the input voltage level. During de-selection (or selection), the control transistor is turned off (or on) to weaken (or enable) the current path, allowing the output transistor to completely turn on and quickly output the required voltage level. This dynamic control eliminates the need to lower Vp while maintaining fast read speed.
Solution Approach 2:
The control transistor is configured to preemptively block the fighting path before it can cause voltage degradation. By controlling the current path in advance, the circuit prevents the partial turn-on condition that would otherwise occur, ensuring clean and fast voltage transitions without speed loss.
3Adaptability or versatility
If transistor N2 (or P2) length is increased to increase its resistance for proper voltage output, then the voltage operation range is improved, but the X-decoder area increases significantly
Solution Approach 1:
The control transistor serves as an intermediary that provides the necessary resistance control without requiring physical extension of transistor N2 (or P2). This mediator enables wide voltage operation range while keeping the transistor dimensions and overall X-decoder area compact.
Solution Approach 2:
Instead of changing the physical dimension (length) of transistor N2 (or P2) to adjust resistance, the invention changes the operational parameters by using the control transistor to regulate current. This parameter-based control achieves the desired voltage operation range without increasing device area.
Data Source
AI summary
A level shifter includes a first level-switching device and a second level-switching device. The first level-switching device includes a first switch device, a second switch device, a first control switch and a third switch device. The first switch device is for receiving the input voltage and outputting a first voltage. The second switch device is coupled to the first switch device for outputting a first operational voltage as the output voltage according to the first voltage. The first control switch is coupled to the first switch device for receiving the first voltage. The third switch device is coupled between the first control switch and the first operational voltage and controlled by the output voltage. The second level-switching device is coupled to the first level-switching device for receiving the input voltage and accordingly outputting a second operational voltage as the output voltage.