Impedance matching techniques for VLSI packaging Conference Paper uri icon

abstract

  • Impedance discontinuities caused by VLSI packaging are one of the largest challenges facing system level designers in the next decade. Modern IC process capability is exceeding the electrical performance of current packaging technology. The speed of the risetimes available on the IC cause the interconnect of the package to be treated as a transmission line. As a result, impedance discontinuities in the package will cause reflections which may result in intermittent switching of digital signals and edge time degradation, both of which limit system performance. The impedance discontinuity in the package is due to excess inductance and capacitance of the physical interconnect. To compensate for this problem, capacitance or inductance can be placed near the interconnect to alter its effective impedance over a given frequency range. This technique has been proven in microwave applications to match impedances at a known frequency. This paper presents the application of this impedance matching technique for use in broadband digital signals that are seen in modern VLSI designs. Two approaches are presented, a static compensation and a dynamic compensation. The static compensator places pre-defined capacitance or inductance on the package and on the IC to surround the parasitics of the interconnect. The dynamic compensator places a switch-able capacitance or inductance on the IC that can be programmed to a desired value to overcome design and manufacturing variations in the interconnect. Both techniques presented are shown to bound the reflections of the interconnect to less than 5% (down from 20% for an uncompensated structure) for the two most common types of interconnect used in VLSI packages (wire bond and flip-chip). In addition, both circuits utilize less area than an interconnect pad, making them ideal for placement directly beneath the pads.

published proceedings

  • International Engineering Consortium - DesignCon 2006

author list (cited authors)

  • LaMeres, B. J., Garg, R., Gulati, K., & Khatri, S. P.

complete list of authors

  • LaMeres, BJ||Garg, R||Gulati, K||Khatri, SP

publication date

  • December 2006