US Patent 11367484 Multi-step pre-read for write operations in memory devices

Systems, methods, and apparatus related to memory devices. In one approach, a memory device has a memory array including memory cells. A controller of the memory device applies multiple pre-read voltages to memory cells prior to performing write operations on the memory cells. The controller applies a first pre-read voltage to determine which of the memory cells have a sensed current that exceeds a threshold. In response to determining that a percentage of the memory cells exceeding the threshold is too low (e.g., below a fixed limit), the controller determines to apply a second pre-read voltage to the memory cells. The second pre-read voltage has a greater magnitude than the first pre-read voltage, and can be applied to ensure greater reliability in properly determining the existing programming state of the memory cells. The controller then applies write voltages to the memory cells as appropriate based on target logic states for each memory cell and the programming mode to be used by the controller.