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UBC Theses and Dissertations

Application of active inductors in high-speed I/O circuits Lee, Yen-Sung Michael


This thesis explores the use of active inductors as a compact alternative to the bulky passive spiral structures in high-speed I/O circuits. A newly proposed PMOS-based topology is introduced and used in active-inductor terminations. The 1st prototype design fabricated in a 90-nm CMOS process consists of an output driver using active-inductor terminations to provide channel equalization and output impedance matching. From measurement results, the use of active inductors in the termination, as compared to when the active inductor is disabled, increases the vertical eye opening in the receiver side by a factor of two and reduces the jitterp-p by 30% of the transmitted 10 Gb/s (2³¹-1) pseudo-random binary sequence pattern, over a 6-inch FR4 channel. An output impedance matching with S₂₂ less than -10 dB over a bandwidth of 20 GHz is achieved. The pair of active-inductor terminations occupies 17×25 µm² and has a low overhead power consumption of 0.8 mW. In the 2nd prototype design, a 4-stage output buffer with active-inductor loads is designed and implemented in a 65-nm CMOS process. Simulation results verify that when operating at 31.25 Gb/s, the output eye of the active-inductor load buffer compares favorably with that of the passive-inductor load buffer. For a similar eye-height and 78% less timing jitter the active-inductor load design’s speed (31.25 Gb/s) is 25% faster than the passive-resistor load design (25 Gb/s). The active-inductor load output buffer achieves comparable performance in terms of speed, power, and output swing with other reported designs using passive inductors. Its total area is 135×30 µm² (including three differential active inductors) which is comparable to the size of a single passive spiral inductor having a 0.5~1 nH inductance.

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