Sense Amplifier for MRAM with Pre-Charged Bit Line
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
In spin injection write systems for magnetic random access memory, sensing minute current differences at high speed is challenging due to small read currents, leading to long sensing times and increased current consumption, which can result in data destruction and erroneous operations.
Innovation Solution
A sense amplifier design that uses a specific configuration of FETs to strengthen the charge or discharge of output nodes using third and fourth currents after initiating the sense operation, allowing for high-speed sensing by adjusting the timing and drive currents of P-channel and N-channel MOSFETs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the read current is made small to avoid data destruction, then the risk of data destruction is reduced, but the current difference becomes smaller and sensing time becomes longer
Solution Approach 1:
The patent applies preliminary action by pre-charging the bit line to a voltage higher than the power supply voltage before the sense operation. This head start in charge accumulation allows the sense amplifier to detect the current difference more quickly, reducing sensing time without needing to increase the read current magnitude, thus maintaining data integrity while improving speed.
2Measurement precision
If the read current flows continuously for a long time to sense the current difference, then sensing accuracy is improved, but current consumption increases and magnetic reversal probability increases
Solution Approach 1:
By pre-charging the bit line to a voltage higher than the power supply voltage, the patent creates a larger voltage differential that accelerates the charging/discharging process during sensing. This allows the sense amplifier to reach a sufficient voltage difference for accurate detection in a shorter time, thereby reducing the duration of read current flow and lowering both current consumption and the probability of magnetic reversal.
Solution Approach 2:
The patent changes the voltage parameter of the bit line by charging it to a voltage higher than the power supply voltage. This parameter change creates a more favorable electrical condition for rapid charge transfer during the sense operation, enabling faster detection of the current difference and reducing the time the read current must flow to achieve accurate measurement.
3Speed
If the strengthening of charge is performed at the start of sense operation, then sensing speed is improved, but the minute current difference is erroneously detected due to premature strengthening
Solution Approach 1:
The patent separates the charge strengthening action from the sense operation timing. The bit line is pre-charged to a voltage higher than the power supply voltage before the sense operation begins. During the sense operation itself, the sense amplifier then detects the current difference without additional strengthening, which prevents erroneous detection while maintaining high sensing speed due to the head start provided by the pre-charging.
Data Source
AI summary
A sense amplifier according to an example of the present invention has first, second, third and fourth FETs with a flip-flop connection. A drain of a fifth FET is connected to a first input node, and its source is connected to a power source node. A drain of a sixth FET is connected to a second input node, and its source is connected to the power source node. A sense operation is started by charging a first output node from the first input node with a first current and by charging a second output node from the second input node with a second current. The fifth and sixth FET are turned on after starting the sense operation.