Current versus Timing Control in Active Anodic Feedback of Biphasic Stimulation

Artificial electrical stimulation that uses biphasic current pulses requires that the cathodic and anodic phases have zero biphasic mismatch. While biphasic mismatch should be minimized, a residual voltage appears due to charge leakage even for perfectly matched signals. Active anodic feedback methods control the charge in the anodic phase such that the tissue environment is electrochemically neutral. In this work, we designed and taped-out a 7-bit current DAC and measured biphasic current mismatch data from 9 chips to suggest that active anodic feedback be performed with timing control rather than amplitude control of current.