| 摘要 |
<p>PURPOSE:To attain high write speed and the titled device with a long service life by discriminating the end of write periodically depending on the change in the threshold value of a memory cell so as to stop the write. CONSTITUTION:A boosting circuit 12 is operated by a write instruction and a high voltage Vpp is generated. Then a switch circuit 15 sends a write signal W to a memory cell array 11 via a data switching circuit 16 by the control of a control circuit 18 based on a signal of data latch circuit 19 to inject or discharge an electron to a floating gate of the memory cell. In this case, the transfer gate Tv is closed by the signal of the circuit 18 periodically, a transfer gate T0 or T1 corresponding to the data is opened and the signal W is used as reference potentials Vr0, Vr1 of the 1st or 2nd reference potential circuit 13, 14. In this state, the current of the memory cell is detected via the sense amplifier 17 and when any current exists, the write is continued, and if no current exists, the write is stopped. Thus, no excess stress is exerted onto the memory cell and long service life and high speed write are attained.</p> |
