Apparatuses and methods for plate coupled sense amplifiers
Embodiments of the disclosure are drawn to apparatuses and methods for plate coupled sense amplifiers. An example embodiment may include a sense amplifier which may sense a voltage from a memory cell. The sense amplifier may also monitor a change in the voltage, and determine a logical value of the memory cell based on the time when the voltage reaches a trigger voltage. The memory cell may be coupled to a plate with a plate voltage, wherein a change in the plate voltage determines the change of the voltage from the memory cell.
1. An apparatus comprising:
a memory cell coupled to a plate, wherein as part of a read operation a voltage of the plate is changed from a first voltage to a second voltage;
a sense amplifier comprising a hysteresis inverter, the sense amplifier configured to read a digit line voltage from the memory cell, monitor a change in the digit line voltage as the plate changes from the first voltage to the second voltage, and determine a logical value of the memory cell based on a time when the digit line voltage crosses a threshold voltage of the hysteresis inverter.
2. The apparatus of claim 1 , wherein the sense amplifier is further configured to provide an output voltage based on the determined logical value.
3. The apparatus of claim 2 , wherein the memory cell comprises either a first logical value or a second logical value, which are read as a first voltage or a second voltage respectively, wherein there is a cell difference between the first and second voltages, and wherein the output voltage comprises either a third voltage or a fourth voltage corresponding to the first and second logical values respectively, wherein there is an output difference between the third and fourth voltages, and wherein the output difference is larger than the cell difference.
4. The apparatus of claim 2 , further comprising a latch circuit coupled to the sense amplifier and configured to latch the output voltage.
5. The apparatus of claim 1 , further comprising a reference amplifier comprising a second hysteresis inverter, the reference amplifier configured to read a reference voltage corresponding to a known logical value, monitor a change in the reference voltage as the plate voltage changes, and determine a cutoff time based on the time the reference voltage activates the second hysteresis inverter.
6. The apparatus of claim 5 , wherein the logical value of the memory cell is determined by determining if the time when the digit line voltage crosses the threshold voltage is before or after the cutoff time.
7. The apparatus of claim 1 , wherein the sense amplifier comprises a digit equalization switch selectively activated by a command signal to initialize an input voltage of the hysteresis inverter to a limit voltage.