RRAM Read Circuit With Charge Supply for Low-Voltage Read Margin
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Solution Overview
Problem
The miniaturization of semiconductor devices, particularly STT-MRAM, reduces the breakdown voltage of transistors, leading to a risk of insufficient readout margin due to the use of low power-source potentials, which can cause failure in securing a sufficient readout margin.
Innovation Solution
A semiconductor device is designed with a memory cell, reference resistive element, clamping circuit, pre-charge circuit, sense amplifier, and electric-charge supply circuit, where a fixed potential is applied to each element, and an electric-charge supply circuit is used to increase the potential difference between the memory and reference elements during the discharge period, thereby enhancing the readout margin.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If miniaturization is advanced to reduce device size, then device scaling is improved, but breakdown voltage of transistors decreases leading to insufficient readout margin
Solution Approach 1:
The bit lines are pre-charged to a high potential level before the read operation. This preliminary charging ensures that even with low breakdown voltage transistors, there is sufficient potential headroom to develop a measurable voltage difference during the read operation, thus maintaining readout margin despite miniaturization
Solution Approach 2:
The invention changes the timing and level of voltage parameters by introducing a pre-charge phase that raises bit line potentials before the differential read operation. This parameter transformation allows the system to operate with low-voltage transistors while still achieving adequate signal margins for reliable detection
2Use of energy by moving object
If low power-source potential is used to support miniaturization, then power consumption is reduced, but readout margin becomes insufficient
Solution Approach 1:
The pre-charge circuit raises the bit line potentials to a high level before the read operation begins. This preliminary energy storage in the bit lines allows the subsequent read operation to proceed with sufficient voltage swing for reliable detection, even though the overall power source potential remains low
Solution Approach 2:
The pre-charge circuit acts as an intermediary that temporarily stores energy in the bit lines. This intermediary mechanism decouples the low power source potential from the high potential swing needed for reliable readout, allowing both low power consumption and adequate readout margin to coexist
Data Source
AI summary
A semiconductor device capable of increasing readout margin in a nonvolatile resistive random access memory is provided. A clamping circuit applies fixed potential to each of a memory element and a reference resistive element. A pre-charge circuit pre-charges first and second nodes to power-source potential. A sense amplifier amplifies the potential difference between the potential of the first node and the potential of the second node generated after a discharge period based on cell current and reference current after pre-charging made by the pre-charge circuit. A third node is coupled to the first and second nodes through a capacitor. An electric-charge supply circuit is connected to the third node, and supplies electric charge to the third node in the discharge period.