Fast, low current program with auto-program for flash memory

摘要

In this invention is described a circuit and method for auto programming of a flash memory cell of an EEPROM. A step split gate is used that has low voltage and low current program conditions. This allows a load device to be connected to each bit line, and sets up a voltage divider between the cell being programmed and the load device. The load device limits the programming current and provides programming data to the cell being programmed. The load device is shut off when the bit line voltage is reduced below a predetermined reference, ending programming of the flash memory cell. The source to drain voltage increases as the memory cell is programmed as a result of the voltage divider between the load device and the cell being programmed thus maintaining pinch off. This produces more energy to program the flash cell and with proper design allows the programming efficiency to be relatively constant over the time that elections are injected onto the floating gate of the flash memory cell. This voltage divider effect also provides for more programming cycles because as charge is built up in the oxide in the vicinity of the floating gate the source to drain voltage is increased automatically providing more energy to program the cell.