Apparatus and method for programming a memory device such as a virtual ground EPROM array cell

摘要

The present invention provides a method and an apparatus for programming a selected cell within a memory device, such as a virtual ground EPROM array cell, without disturbing adjacent array cells. In preferred embodiments, the electrical disturbance of data stored in adjacent cells is limited in a number of ways: (1) a column connection circuit is provided for selectively coupling together adjacent pairs of even-odd or odd-even column lines so that source and drain terminals of adjacent memory cells are electrically coupled together, thereby preventing the data stored within the adjacent cells from being disturbed; (2) a current limiter circuit is provided for lowering a potential on a terminal of the selected cell at a controlled rate during programming so that voltages on terminals of the selected cell do not disturb data stored on adjacent memory cells; (3) the order in which programming signals are applied to terminals of the selected cell are controlled in such a way as to reduce the disturbance of data on adjacent cells; and (4) high wordline and data line voltages are applied to the selected cell in two steps, first to an intermediate voltage, and then to a high voltage. This reduces the disturbance to adjacent cells and improves programming. <IMAGE>