Noise measuring system, noise measuring method, and semiconductor device

1. A semiconductor device comprising:

a noise source circuit causing noise on wiring under noise measurement in response to a trigger signal;

a comparator circuit comparing a voltage on said wiring with a reference voltage and outputting a result of comparison; and

a noise state output circuit changing a logic state output therefrom in response to a change of the result of comparison,

wherein said noise state output circuit receives a data signal, the data signal becoming active after an input of the trigger signal;

said noise state output circuit comprising:

a first latch circuit that latches the data signal according to the change of the result of comparison to one state, for output to outside; and

a second latch circuit that latches the data signal according to the change of the result of comparison to the other state, for output to outside.

2. A noise measuring system comprising:

a semiconductor device including a comparator circuit that compares a voltage on wiring of said semiconductor device with a reference voltage and supplies an output indicating a result of said comparison to outside; and

measuring equipment that measures a period of time elapsed from a supply of a signal to a signal input terminal of said semiconductor device to a change of the output and associates said time with the reference voltage.

3. The noise measurement system according to claim 2 , wherein said wiring comprises power supply wiring.

4. The noise measuring system according to claim 2 , wherein the measuring equipment further:

changes the reference voltage;

supplies a trigger signal to the semiconductor device;

supplies a data signal to the semiconductor device; and

reads said reference voltage, a generation time of the trigger signal, a time when the data signal has been latched at a first latch circuit, and a time when the data signal has been latched at a second latch circuit, thereby estimating a waveform of a noise generated on the wiring.

5. A noise measuring method of measuring noise on wiring targeted for noise measurement in a semiconductor device by a measuring equipment, said noise measuring method comprising:

a) supplying to said semiconductor device a reference voltage having a predetermined deviation with respect to a potential of said wiring so as to compare the reference voltage with the potential of said wiring;

b) supplying a trigger signal for noise generation to a noise source of said wiring in said semiconductor device;

c) comparing the potential of said wiring with the reference voltage and outputting a result of comparison; and

d) measuring a time elapsed from a time when the trigger signal is supplied to a time when the result of comparison is changed.

6. The noise measuring method according to claim 5 , wherein by changing the reference voltage and repeating said steps a), b), c), and d), a waveform of the noise generated on said wiring is estimated.

7. The noise measuring method according to claim 6 , wherein the waveform is estimated by plotting the reference voltage and the timings of changes in the outputs.

8. The noise measuring method according to claim 6 , wherein a setting range of the reference voltage is +/−1 V.

9. The noise measuring method according to claim 6 , wherein a setting range of the reference voltage is based on an amplitude of a jitter noise.

10. The noise rneasureing system according to claim 6 , wherein the change of the reference voltage is +/−0.1 V.

11. The noise measuring system according to claim 6 , wherein the change of the reference voltage is +/−0.05 V.