Memory Read Micropump Circuit for Sense Transistor Vt Variability
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Solution Overview
Problem
The variability in threshold voltage (Vt) of sense transistors in memory devices complicates accurate data transfer, particularly in all bitline (ABL) schemes, leading to inefficiencies in reading data from multiple arrays simultaneously.
Innovation Solution
Integrating a micropump within the reading hardware layer between each sensing transistor and the global bitline, which modulates a constant current flow by controlling a series of transistors, including a read transistor and a read capacitor transistor, to mitigate Vt variability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If sense transistors are used in all bitline schemes to read data from multiple arrays simultaneously, then data transfer capability is improved, but threshold voltage variability causes inaccuracies in data transfer
Solution Approach 1:
A micropump circuit is introduced as an intermediary component between the sense transistor and the bitline. The micropump includes a pump transistor and capacitor that actively regulate and stabilize the read current, mediating the effect of threshold voltage variability and preventing it from directly affecting data transfer accuracy
Solution Approach 2:
The patent changes the operational parameters of the read path by introducing controlled current modulation through the micropump. The pump transistor and capacitor work together to dynamically adjust and stabilize the read current parameters, compensating for threshold voltage variations in the sense transistor
2Measurement precision
If threshold voltage variability is compensated for accurate reading, then data transfer accuracy is improved, but additional circuit complexity is introduced
Solution Approach 1:
The micropump circuit is segmented into distinct functional components: a pump transistor for current control and a capacitor for timing and stabilization. This segmentation allows each component to perform its specific function efficiently while keeping the overall circuit manageable and understandable
Solution Approach 2:
The micropump circuit serves multiple functions simultaneously: it stabilizes the read current, compensates for threshold voltage variability, and enables accurate data transfer from multiple arrays. This multi-functionality reduces the need for separate compensation circuits, thereby limiting the increase in overall device complexity
Data Source
AI summary
A memory device includes an array of strings of memory cells, a local bitline coupled with a plurality of the strings of memory cells, and a sense transistor having a gate terminal coupled with the local bitline. The memory device further includes a series of transistors have a data read path between a source line and the sense transistor and between the sense transistor and a global bitline that is coupled with a page buffer. A micropump is integrated within the series of transistors. Control logic is coupled with the series of transistors and to, during a read operation of a memory cell of the array and in response to the sense transistor turning on, activate the micropump to cause a constant read current to flow between the global bitline and the source line.