Source Side Sensing Circuitry for Memory Read Reliability
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Solution Overview
Problem
Conventional memory read operations face reliability issues due to leakage currents when multiple memory cells represent '1', leading to inaccuracies in sensing currents and reduced performance.
Innovation Solution
A reading circuitry that senses source currents from memory cells, utilizing a source side sensing circuit and shielding to minimize leakage currents, thereby improving read operation reliability by equalizing sensing currents with source currents.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional drain side sensing is used to read memory cells, then the sensing operation can be performed, but leakage currents occur when multiple memory cells represent '1', causing sensing current inaccuracies and reducing read operation reliability
Solution Approach 1:
The patent inverts the conventional sensing approach by switching from drain side sensing to source side sensing. In conventional drain side sensing, the sensing current is measured at the drain terminal, but leakage currents from adjacent cells corrupt this measurement. The invention applies inversion by measuring the sensing current at the source terminal instead, where the current path originates, thereby avoiding the leakage current interference that occurs at the drain side when multiple cells are in state '1'.
Solution Approach 2:
The patent extracts the sensing operation from the drain side circuitry and relocates it to the source side. By separating the sensing function from the drain terminal and placing it at the source terminal, the invention isolates the sensing current measurement from the harmful leakage currents that affect drain side measurements, thereby improving both reliability and measurement precision.
2Productivity
If multiple memory cells are read simultaneously, then productivity increases, but leakage currents from cells representing '1' accumulate, deteriorating overall memory performance
Solution Approach 1:
The patent applies inversion by changing the sensing location from drain side to source side, which fundamentally alters how multiple cell readings interact. When multiple cells are read simultaneously, source side sensing prevents the accumulation of leakage currents from cells in state '1', allowing parallel read operations to maintain high productivity without compromising reliability.
Data Source
AI summary
A reading circuit in a memory, having a first memory cell coupled to a first bit line and a second bit line, a second memory cell coupled to the second bit line and a third bit line and a third memory cell coupled to the third bit line and a fourth bit line, is provided. The reading circuitry includes a sensing circuit, a drain side bias circuit, a first selection circuit and a second selection circuit. The drain side bias circuit provides a drain side bias. The first selection circuit connects the second bit line to the drain side bias circuit to receive the drain side bias in a read operation mode. The second selection circuit connects the first bit line and the fourth bit line to the sensing circuit in the read operation mode, so that the sensing circuit senses a current of the first memory cell.