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    • 3. 发明授权
    • Non-volatile SRAM
    • 非易失性SRAM
    • US5956269A
    • 1999-09-21
    • US964841
    • 1997-11-05
    • Kenneth Wisheng OuyangDing-Hsu Yen
    • Kenneth Wisheng OuyangDing-Hsu Yen
    • G11C11/412G11C16/00
    • G11C11/4125
    • A method and devices are provided for producing a non-volatile SRAM, of the type composed of two back-to-back, cross-coupled, CMOS inverters, each with a PMOS and an NMOS and respective outputs Q and Q.about. connected therebetween, even when the cell is completely symmetrical, by creating a stable condition wherein Q.noteq.Q.about. through rendering the threshold voltages of the NMOS devices different. The threshold voltages of the NMOSs are made different by using hot electron injection. The hot electron effect is produced by meeting the conditions, that 1) one of the NMOSs must be in saturation condition, i.e., V.sub.DS .gtoreq.V.sub.GS -V.sub.th, where V.sub.DS is the drain to source voltage, V.sub.GS is the gate to source voltage, and V.sub.th the threshold voltage, of the NMOS, and 2) V.sub.DS must be large enough, typically about 7 V, depending on the fabrication process. To achieve these conditions, for example, firstly a regular write function is performed on the SRAM so that the cell will have a predetermined condition, i.e., a high, low or low, high value. A negative voltage pulse is then applied to the inverter with the high output value to put its NMOS in a saturation state. This results in producing hot electrons that are stored in the gate oxide of the NMOS, thus making the threshold voltage of the two NMOS devices unbalanced, i.e., V.sub.th1 .notident.V.sub.th2, and achieving the function of hard memory.
    • 提供了一种用于产生由两个背对背,交叉耦合的CMOS反相器组成的类型的非易失性SRAM的方法和装置,每个都具有PMOS和NMOS,并且各自的输出Q和Q差分连接在它们之间, 即使当电池完全对称时,通过产生稳定的条件,其中通过使NMOS器件的阈值电压不同,其中Q NOTEQUAL Q DIFIFERENCE。 通过使用热电子注入使NMOS的阈值电压不同。 热电子效应是通过满足以下条件产生的:1)其中一个NMOS必须处于饱和状态,即VDS> / = VGS-Vth,其中VDS是漏极到源极电压,VGS是栅极到源极电压 ,并且Vth的阈值电压为Vth,以及2)VDS必须足够大,通常约为7V,这取决于制造工艺。 为了实现这些条件,例如,首先在SRAM上执行常规写入功能,使得单元将具有预定条件,即高,低或低的高值。 然后将负电压脉冲以高输出值施加到逆变器,以使其NMOS处于饱和状态。 这导致存储在NMOS的栅极氧化物中的热电子,从而使得两个NMOS器件的阈值电压不平衡,即Vth1 NOTEQUAL Vth2,并实现硬存储器的功能。