Semiconductor storage device including counter noise generator and method of controlling the same

1. A semiconductor storage device, comprising:

a reference voltage source connected to a capacitor of a cell included in a memory;

a buffer circuit holding data to be written in the cell; and

a counter noise generator outputting a counter noise current canceling a noise current generated by rewriting the data in the cell to the reference voltage source according to the data held in the buffer circuit.

2. The semiconductor storage device according to claim 1 , wherein an output voltage of the reference voltage source is equal to or lower than a half of a power supply voltage.

3. The semiconductor storage device according to claim 1 , wherein the semiconductor storage device compares the data held in the buffer circuit with data held in the cell subjected to a writing operation before the writing operation and determines current amount of the counter noise current output from the counter noise generator by the comparing result.

4. The semiconductor storage device according to claim 1 , wherein

the data held in the buffer circuit and data held in the cell subjected to a writing operation before the writing operation are formed by a plurality of data in H level and L level, and

the semiconductor storage device compares the data held in the buffer circuit with the data held in the cell subjected to the writing operation before the writing operation, and determines current amount of the counter noise current output from the counter noise generator according to the comparing result which is a difference between a number of data rewritten from the H level to the L level and a number of data rewritten from the L level to the H level.

5. The semiconductor storage device according to claim 1 , wherein the semiconductor storage device determines current amount of the counter noise current output from the counter noise generator by the data held in the buffer circuit.

6. The semiconductor storage device according to claim 1 , wherein

the data held in the buffer circuit is formed by a plurality of data in H level and L level, and

the semiconductor storage device determines current amount of the counter noise current output from the counter noise generator according to a value of ½ of a difference between a number of data in the H level and a number of data in the L level.

7. The semiconductor storage device according to claim 1 , wherein the counter noise current output from the counter noise generator is output during a period in which writing in the cell is performed.

8. The semiconductor storage device according to claim 1 , wherein the counter noise current output from the counter noise generator is output after a period in which writing in the cell is performed.

9. The semiconductor storage device according to claim 1 , wherein a gate transistor connected to the capacitor of the cell is an NMOS transistor.

10. The semiconductor storage device according to claim 1 , wherein a gate transistor connected to the capacitor of the cell is a PMOS transistor.

11. A method of controlling a semiconductor storage device, comprising:

reading out data of a buffer circuit holding data to be written in a cell;

comparing the data which is read out with data held in the cell subjected to a writing operation before the writing operation;

calculating the comparing result which is a difference between a number of data rewritten from H level to L level and a number of data rewritten from L level to H level; and

determining current amount output from a counter noise generator generating a counter noise current canceling a noise current generated by rewriting the data in the cell to a reference voltage power source according to the calculating result.

12. A method of controlling a semiconductor storage device, comprising:

reading out data of a buffer circuit holding data to be written in a cell;

calculating a value of ½ of a difference between a number of data in H level and a number of data in L level of the data which is read out; and

determining current amount output from a counter noise generator generating a counter noise current canceling a noise current generated by rewriting the data in the cell to a reference voltage power source according to the calculating result.

13. The method of controlling the semiconductor storage device according to claim 11 , wherein the counter noise current output from the counter noise generator is output during a period in which writing in the cell is performed.

14. The method of controlling the semiconductor storage device according to claim 11 , wherein the counter noise current output from the counter noise generator is output after a period in which writing in the cell is performed.