Method for reducing output data noise of semiconductor apparatus and semiconductor apparatus implementing the same

1. A method for reducing output data noise of a semiconductor apparatus which includes a plurality of output buffers to output data, the method comprising the steps of:

driving low data to a specific output buffer among the plurality of output buffers, and driving data transiting from a high level to a low level to the other output buffers; and

measuring the magnitude of data noise occurring in output data of the specific output buffer, and deciding slew rates of the plurality of output buffers based on the measurement result.

2. The method according to claim 1 , wherein the step of measuring the magnitude of data noise and deciding the slew rates is comprises the steps of:

measuring the magnitude of the data noise occurring in the output data of the specific output buffer and converting the measured magnitude into a digital code value; and

controlling the slew rates of the plurality of output buffers based on the digital code value.

3. The method according to claim 2 , wherein the step of measuring the magnitude of the data noise and converting the measured magnitude comprises the step of removing a DC component from the output data of the specific output buffer and extracting an AC component as the data noise.

4. The method according to claim 2 , wherein the step of measuring the magnitude of the data noise and converting the measured magnitude comprises the steps of:

amplifying the magnitude of the data noise;

rectifying the amplified data noise and quantifying the magnitude of the amplified data noise; and

converting the quantified magnitude of the amplified data noise into the corresponding digital code value.

5. The method according to claim 2 , wherein the step of controlling the slew rates of the plurality of output buffers comprises the step of decreasing the slew rates of the plurality of output buffers, when the digital code value corresponding to the magnitude of the data noise larger than a reference value is inputted.

6. The method according to claim 2 , wherein the step of controlling the slew rates of the plurality of output buffers comprises the step of increasing the slew rates of the plurality of output buffers, when the digital code value corresponding to the magnitude of the data noise smaller than a reference value is inputted.

7. A method for reducing output data noise of a semiconductor apparatus which includes a plurality of output buffers to output data, the method comprising the steps of:

driving high data to a specific output buffer among the plurality of output buffers, and driving data transiting from a low level to a high level to the other output buffers; and

measuring the magnitude of data noise occurring in output data of the specific output buffer, and deciding slew rates of the plurality of output buffers based on the measurement result.

8. The method according to claim 7 , wherein the step of measuring the magnitude of data noise and deciding the slew rates comprises the steps of:

measuring the magnitude of the data noise occurring in the output data of the specific output buffer and converting the measured magnitude into a digital code value; and

controlling the slew rates of the plurality of output buffers based on the digital code value.

9. The method according to claim 8 , wherein the step of measuring the magnitude of the data noise and converting the measured magnitude comprises the steps of:

removing a DC component from the output data of the specific output buffer and extracting an AC component as the data noise;

amplifying the magnitude of the extracted data noise;

rectifying the amplified data noise and quantifying the magnitude of the amplified data noise; and

converting the quantified magnitude of the amplified data noise into the corresponding digital code value.

10. The method according to claim 8 , wherein the step of controlling the slew rates of the plurality of output buffers comprises the step of decreasing the slew rates of the plurality of output buffers, when the digital code value corresponding to the magnitude of the data noise larger than a reference value is inputted.

11. The method according to claim 8 , wherein the step of controlling the slew rates of the plurality of output buffers comprises the step of increasing the slew rates of the plurality of output buffers, when the digital code value corresponding to the magnitude of the data noise smaller than a reference value is inputted.

12. A semiconductor apparatus comprising:

a plurality of output buffers configured to be driven by a power supply voltage and a ground voltage and output received data; and

a data noise measuring unit configured to measure a magnitude of data noise from output data of a specific output buffer among the plurality of output buffers, and generate a slew rate control signal to control slew rates of the plurality of output buffers based on the measurement result.

13. The semiconductor apparatus according to claim 12 , wherein when the magnitude of the data noise is larger than a reference value, the slew rates of the plurality of output buffers are decreased in response to the slew rate control signal.

14. The semiconductor apparatus according to claim 12 , wherein when the magnitude of the data noise is smaller than a reference value, the slew rates of the plurality of output buffers are increased in response to the slew rate control signal.

15. The semiconductor apparatus according to claim 12 , wherein during initial setting, low data is driven to the specific output buffer, and data transiting from a high level to a low level are driven to the other output buffers.

16. The semiconductor apparatus according to claim 12 , wherein during initial setting, high data is driven to the specific output buffer, and data transiting from a low level to a high level are driven to the other output buffers.

17. The semiconductor apparatus according to claim 12 , wherein the data noise measuring unit comprises:

an AC component extractor configured to remove a DC component from the output data of the specific output buffer and extracts an AC component as the data noise;

an amplifier configured to amplify the magnitude of the extracted data noise;

a rectifier configured to rectify the amplified data noise and quantify the magnitude of the amplified data noise; and

an analog-digital converter configured to convert the quantified magnitude of the amplified data noise into the corresponding digital code value and output the slew rate control signal.

18. The semiconductor apparatus according to claim 17 , wherein the AC component extractor comprises a capacitor connected to in series.

19. The semiconductor apparatus according to claim 17 , wherein the rectifier comprises a capacitor filter connected in parallel to a capacitor.

20. The semiconductor apparatus according to claim 17 , wherein the analog-digital converter comprises a register to store a reference value, and convert the quantified magnitude of the amplified data noise into the digital code value based on the reference value.