Programmable duty cycle distortion generation circuit

1. An integrated circuit comprising:

a serial transmitter;

a serial receiver;

a serial connection providing communication between said serial transmitter and said serial receiver;

a duty cycle distortion circuit configured to distort a duty cycle of a signal within said integrated circuit by differentially adding an offset current to said signal to generate a voltage offset in the signal so as to stress test said integrated circuit; and

wherein said duty cycle distortion circuit comprises a first current source coupled between a first differential output and a ground potential and further comprises a second current source coupled between a second differential output and the ground potential, and wherein the first current source and the second current source are configured to generate the voltage offset in the signal by adding the current offset to the signal.

2. An integrated circuit as claimed in claim 1 , wherein said duty cycle distortion circuit distorts said duty cycle to degrade said communication so as to stress test said serial receiver.

3. An integrated circuit as claimed in claim 1 , wherein said duty cycle distortion circuit is configured to distort said duty cycle to stress test a duty cycle correction circuit.

4. An integrated circuit as claimed in claim 1 , wherein said duty cycle distortion circuit forms part of said serial transmitter.

5. An integrated circuit as claimed in claim 1 , wherein said duty cycle distortion circuit forms part of said serial receiver.

6. An integrated circuit as claimed in claim 1 , wherein said duty cycle distortion circuit forms part of a clock generation circuit.

7. An integrated circuit as claimed in claim 1 , wherein said duty cycle distortion circuit forms part of a buffer.

8. An integrated circuit as claimed in claim 7 , wherein said buffer is a differential current mode logic buffer.

9. An integrated circuit as claimed in claim 1 , wherein said duty cycle distortion circuit is controlled by a duty cycle distortion control circuit.

10. An integrated circuit as claimed in claim 9 , wherein said duty cycle distortion control circuit is configured to control said duty cycle distortion circuit by voltage control.

11. An integrated circuit as claimed in claim 9 , wherein said duty cycle distortion control circuit is configured to control said duty cycle distortion circuit by a digital control signal.

12. An integrated circuit as claimed in claim 11 , wherein said duty cycle distortion circuit comprises a digital to analog converter for converting the digital control signal to an analog control signal for controlling addition of the offset current to the signal.

13. An integrated circuit as claimed in claim 1 , wherein said communication is self-timed serial data communication.

14. A method of stress testing an integrated circuit, comprising:

providing communication between a serial transmitter and a serial receiver on said integrated circuit over a serial connection; and

distorting within said integrated circuit a duty cycle of a signal to stress test said integrated circuit by differentially adding an offset current to said signal to generate a voltage offset in the signal, said offset current generated by using a first current source coupled between a first differential output and a ground potential, and a second current source coupled between a second differential output and the ground potential.

15. The method of claim 14 , further comprising:

receiving a digital signal; and

controlling addition of the offset current to the signal based on the digital signal.

16. The method of claim 15 , wherein controlling addition of the offset current to the signal comprises:

converting the digital signal to an analog signal; and

controlling the addition of the offset current to the signal based on the analog signal.

17. An integrated circuit comprising:

a serial transmitter means for transmitting serial data;

a serial receiver for receiving serial data;

a serial connection means for providing communication between said serial transmitter means and said serial receiver; and

a duty cycle distortion circuit for distorting a duty cycle of a signal within said integrated circuit by differentially adding an offset current to said signal to generate a voltage offset in the signal to stress test said integrated circuit, said offset current generated by using a first current source coupled between a first differential output and a ground potential, and a second current source coupled between a second differential output and the ground potential.

18. The integrated circuit of claim 17 , wherein the duty distortion circuit comprises:

a duty cycle distortion control circuit configured to receive a digital signal and control the duty cycle distortion circuit based on the digital signal.

19. The integrated circuit of claim 18 , wherein said duty cycle distortion circuit comprises a digital to analog converter for converting the digital control signal to an analog control signal for controlling addition of the offset current to the signal.