Current Detection Circuit for Semiconductor Memory
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Solution Overview
Problem
Current sensing technologies face challenges in rapidly detecting current through tiny bit line structures due to increased resistance and capacitive coupling, leading to longer pre-charge times and non-uniform threshold values in semiconductor memory cells.
Innovation Solution
A current detection circuit comprising a first supply circuit, a second supply circuit, and a determination circuit, which sets a constant current and determines if a larger current is discharged from the bit line, allowing for rapid detection of current through tiny bit lines and reducing data readout time in semiconductor memory apparatus.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If voltage detection type sense circuit is used, then the circuit can supply pre-charge potential to bit lines, but the sensing time becomes longer when bit lines become tiny structures due to increased resistance and capacitive coupling
Solution Approach 1:
The patent replaces the voltage detection type sense circuit with a current detection type sense circuit. Instead of detecting voltage changes on the bit line, the new circuit detects current flow directly. This substitution fundamentally changes the detection mechanism from voltage-based to current-based, enabling rapid sensing even when bit lines have high resistance due to tiny dimensions.
Solution Approach 2:
The patent changes the detection parameter from voltage to current. By measuring current flow through the bit line rather than voltage changes, the sense circuit can rapidly detect memory cell states without being constrained by the RC time constants that limit voltage-based detection in high-resistance tiny bit line structures.
2Reliability
If bit line shielding is performed to reduce noise, then capacitive coupling noise is reduced, but the pre-charge time for the selected bit line becomes longer
Solution Approach 1:
The current detection type sense circuit replaces the voltage detection approach that requires bit line shielding. By detecting current flow directly, the circuit becomes insensitive to capacitive coupling noise between adjacent bit lines, eliminating the need for shielding operations that would extend pre-charge time.
3Loss of time
If current detection type sense circuit is used, then sensing time is reduced, but the ability to determine little current flowing through the bit line is required due to non-uniform threshold values
Solution Approach 1:
The sense circuit is divided into multiple independent current detection circuits, each capable of precisely detecting small currents. The determination circuit compares currents from different detection circuits to identify the state of selected memory cells, enabling accurate detection even with non-uniform threshold values across the memory array.
Solution Approach 2:
The patent changes from detecting voltage (which is affected by threshold voltage non-uniformity) to detecting current. Current detection provides a more direct measurement of memory cell conduction state, reducing the impact of threshold voltage variations and enabling faster sensing with improved precision for detecting small currents.
Data Source
AI summary
The invention provides a current detection circuit and a semiconductor memory apparatus using the current detection circuit thereof. The current detection circuit is capable of rapidly sensing the current flowing through a tiny bit line structure. A page buffer/sensing circuit of the invention includes: a transistor TP3 pre-charging a node SNS during a pre-charge period and providing a target constant current to the node SNS during a discharge period; a transistor TN3 pre-charging the bit line according to the voltage pre-charged to the node SNS; and a transistor TP2 connected to the node SNS. The transistor TP2 detects whether or not a current larger than the constant current supplied by the transistor TP3 is discharged from the bit line and outputs a detection result to a node SENSE.