| 摘要 |
<p>PROBLEM TO BE SOLVED: To attain the reduction of write time and reduction of generation of failure due to shortage of writing and excessive writing by providing an oscillating circuit which changes frequency of the reference time signal in response to the write voltage value. SOLUTION: An oscillating circuit 1 varies the frequency of the output reference time signal O in response to the write voltage Vpp supplied from a voltage supply circuit 5. A frequency dividing circuit 2 divides the signal O output from the oscillating circuit 1 depending on the predetermined frequency dividing rate to generate a write control signal. Accordingly, the writing time is varied depending on the write voltage Vpp to set the optimum writing time corresponding to variation of the write voltage Vpp. Thereby, stress applied on the write cells and non-write cells due to insufficient writing and excessive writing can be reduced. The oscillating circuit 1 preferably comprises a variable delay circuit consisting of inverter circuits 11 to 15, transistors DT1, DT and capacitors C1, C2.</p> |
