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15 bit Pseudo Random Bit Generator

15 bit Pseudo Random Bit Generator. Alfred Ip Eugene Choi Derald Mo Lei Pan. Pseudorandom bit generator (PRBS). A Pseudorandom bit generator (PRBS) is used to generate a random sequence of 1’s and 0’s

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15 bit Pseudo Random Bit Generator

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  1. 15 bit Pseudo Random Bit Generator Alfred Ip Eugene Choi Derald Mo Lei Pan

  2. Pseudorandom bit generator (PRBS) • A Pseudorandom bit generator (PRBS) is used to generate a random sequence of 1’s and 0’s • It is a good approach to use a PRBS sequence as a testing driver than a regular pulse wave sequence

  3. How to construct a PSRB

  4. Design a 15 bit Pseudo Random Bit Generator / Analyzer • Design a 15bit PRBS serial bit stream at 25MHz • Design a analyzer to check if an error is encountered in the output signal

  5. Description • Circuit 1: 15 DFF connect in series, the output of the 13th and 15th DFF will connect to a XOR logic gate and feedback to the 1st DFF • Circuit 2: The 15th DFF output will connect to another 15 DFF that connected in series. XORing the 15th DFF output from circuit 1 and the 15th DFF output from circuit 2 to check if an error occurs.

  6. Technology • DFF with Set - with S = 5V, Q = D - with S = 0V, Q = 0V • Buffer: To drive a large load capacitance

  7. DFF Symbol

  8. DFF Schematic

  9. DFF Layout

  10. DFF Test Bench with S = 5V

  11. DFF Simulation with S = 5V

  12. DFF Simulation with S = 0V

  13. Power Dissipation for the DFF • Pave = αCloadVDD^2 ƒ • With α = 1, Cload = 1.15pF, VDD = 5V and f = 25MHz • Pave = 715.8μW

  14. Rise and Fall time delay • Rise time delay tR (0 > 1) • tR = 7.27ns • Fall time delay tf (1 > 0) • tf = 4.99ns

  15. Buffer • A Buffer is used when the output signal is not large enough to drive the load capacitance • Usually we use inverter to serve as a buffer

  16. Buffer Symbol

  17. Buffer Layout

  18. 15bit PSRB

  19. 15bit PSRB schematic

  20. 15bit PSRB Layout

  21. 15bit PSRB Power Dissipation • Average Power Dissipation of the 15bit PSRB : • 30 X DFF Power Dissipation • = 30 X 715.8μW • which is approximately equal to 22mW

  22. 15bit PSRB Test Bench

  23. 15bit PSRB Simulation

  24. 15bit PSRB Simulation cont.

  25. 15bit PSRB Simulation cont. 2

  26. 15bit PSRB Simulation cont. 3

  27. 15bit PSRB Simulation with S = 0

  28. Reference: • http://archives.e-insite.net/archives/ednmag/reg/1994/051294/10df3.htm, Andreas Pfaff

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