Antifuse Differential Cell Random Code Generator Sensing Circuit
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Solution Overview
Problem
Existing antifuse differential cell-based random code generators face challenges in accurately determining the storage state due to large read currents generated by both antifuse transistors during the read cycle, making it difficult to judge the storage state and generate a reliable random code.
Innovation Solution
A sensing circuit with a positive feedback mechanism that enhances the voltage difference between the bit line and the inverted bit line by discharging the higher voltage, allowing for accurate determination of the storage state and generation of a random code, even when read currents are very large.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional antifuse differential cell is used to generate random code, then the device structure is simple, but the storage state cannot be accurately determined due to large read currents
Solution Approach 1:
The sensing circuit employs a positive feedback mechanism where the discharge of the higher voltage bit line is fed back to enhance the voltage difference. When one bit line reaches a threshold voltage, it triggers the discharge of the other bit line through the feedback path, amplifying the voltage difference and enabling accurate storage state determination even with large read currents.
Solution Approach 2:
The sensing circuit introduces intermediate elements including discharge paths with control transistors and threshold voltage reference circuits. These intermediaries mediate between the large read currents and the detection mechanism, converting the current-based signal into a voltage-based signal that can be accurately measured and interpreted.
2Reliability
If read cycle is performed with conventional cell, then the read current is generated, but the voltage difference between bit line and inverted bit line is insufficient for accurate judgment
Solution Approach 1:
The sensing circuit performs preliminary actions by pre-charging both bit lines to a threshold voltage before the actual read operation. This preliminary charging ensures that when read currents flow, the voltage difference develops predictably and reaches detectable levels, facilitating reliable storage state judgment without complicating the overall read cycle operation.
Solution Approach 2:
The sensing circuit dynamically changes voltage parameters during the read cycle. It monitors voltage levels on bit lines and adjusts discharge timing based on threshold voltages, transforming the static voltage difference problem into a dynamic parameter control process that enhances reliability while maintaining operational simplicity.
Data Source
Figure 1A~2B
Figure 3A~3B
Figure 4~5
AI summary
A random code generator includes a memory cell array (410) and a sensing circuit (420). The memory cell array includes plural antifuse differential cells. The sensing circuit has an input terminal and an inverted input terminal. When a first antifuse differential cell of the memory cell array is a selected cell, a bit line (BL) of the selected cell is connected with the input terminal of the sensing circuit and an inverted bit line (BLB) of the selected cell is connected with the inverted input terminal of the sensing circuit. During a read cycle, the selected cell generates a first charging current to charge the bit line (BL) and a second charging current to charge the inverted bit line (BLB), wherein if a first voltage of the bit line (BL) is higher than a second voltage of the inverted bit line (BLB), the sensing circuit (420) discharges the second voltage of the inverted bit line (BLB) to enhance a voltage difference between the bit line (BL) and the inverted bit line (BLB), and if the second voltage of the inverted bit line (BLB) is higher than the first voltage of the bit line (BL), the sensing circuit (420) discharges the first voltage of the bit line (BL) to enhance the voltage difference between the bit line (BL) and the inverted bit line (BLB). The sensing circuit judges a storage state of the selected cell according to the enhanced voltage difference and determines a bit of a random code according to the storage state of the selected cell.