Power Distribution Analysis of Multi-Layer Substrates With Power Decoupling Capacitors Available to Purchase

This paper describes power distribution design and analysis for multi-layer LTCC (low temperature co-fired ceramic) substrates intended for broadband digital applications. Both land side discrete capacitor (LSC, i.e. mounted on the bottom) and top side discrete capacitor (TSC, i.e. mounted on the top or the same side as the active device) configurations were compared in terms of impedance characteristics up to 3 GHz, with respect to different port locations for the active device. Full-wave electromagnetic modeling was carried out to study the impedance characteristics and good correlation with vector network analyzer measurements was achieved. At lower frequencies well below the self-resonant frequency of the intrinsic power plane, the effective impedance is dominated by the series effective inductance. It was observed that the LSC configuration achieves lower impedance due to a reduced series effective inductance since the TSC configuration results in a longer low frequency impedance path. At higher frequencies, however, the LSC configuration actually results in an impedance peak at a lower frequency due to the parallel resonance attributed to the power planes.