Fig. 8. N-Curve for stability analysis
Static Voltage Noise Margin (SVNM)
The SVNM refers to the maximum threshold of DC noise voltage that an SRAM cell’s inverter input can endure without inducing any alteration in its stored data. The simulation plot presented in Figure IV(e), the voltage disparity between points A and B is depicted, showcasing the maximum permissible DC noise voltage that the SRAM cell can endure while preserving the integrity of its stored data. In simpler terms, SVNM serves as a measure of the SRAM cell’s stability against external noise disturbances.
SVNM = VB - VA
Static Current Noise Margin (SINM)
The SINM is an essential parameter that evaluates the stability of the SRAM cell under the influence of external current disturbances. It represents the maximum allowable DC current that can be injected into the cell without causing any modification to its stored data. The accompanying plot depicts the peak current positioned between points A and B, providing insight into the SRAM cell’s ability to withstand current interference while preserving data integrity. By measuring SINM, we can ensure that the SRAM cell can withstand external current noise and maintain its stored data, thus evaluating its stability.
Write Trip Voltage (WTV)
The WTV denotes the minimum voltage reduction required to switch the internal node ”1” of the SRAM cell from one state to another, while both bit lines are held at the Vdd voltage level. This value can be determined by measuring the voltage discrepancy between points C and B in the corresponding plot, as depicted in Figure IV(e). Through the measurement of the WTV, we can evaluate the essential voltage required for writing data into the SRAM cell. This information is crucial for assessing the functionality and performance of the cell. The WTV serves as a critical parameter in assessing the SRAM cell’s write ability, ensuring accurate and reliable data storage operations. In other words, WTV indicates the voltage threshold at which the SRAM cell can be successfully programmed with a new data bit.
SVNM = VB – VC
Write Trip Current (WTI)
WTI refers to the minimum current level necessary to write data into the SRAM cell without causing any undesired disruptions. It can be determined by identifying the negative peak current between points C and B in the N-curve illustrated in Figure IV(e). The overlapping of points A and B, or B and C, can compromise the stability of the SRAM cell. Hence, WTI serves as a crucial metric for evaluating the write capability of the SRAM cell, ensuring accurate and reliable data writing while preserving its stability. In essence, WTI specifies the minimum current required to change the state of the SRAM cell without any unwanted disturbances.
Power Dissipation for various Technologies