Signal integrity analysis of a 2-D and 3-D integrated potentiostat for neurotransmitter sensing

3-D integration technology offers significant advantages in implantable devices by reducing the form factor and power dissipation. Signal integrity characteristics of a 2-D and 3-D integrated potentiostat for neurotransmitter sensing are investigated and compared. The potentiostat is implemented as current integrating switched-capacitor first-order single-bit delta-sigma modulator. An electrical model is developed for the substrate, power network, and through silicon vias (TSVs). These models are combined with the neurotransmitter sensing circuit to generate an entire model to analyze signal integrity. Contrary to the conventional assumption, a 3-D integrated hybrid system does not necessarily exhibit enhanced noise isolation despite the advantage of having separate planes, as demonstrated in this paper. Noise coupling into the substrate due to TSVs is shown to be a significant mechanism that degrades signal integrity in 3-D integrated implantable systems.