A Charge Balanced Stimulators With a Twin Compensation Loop for Evoked Neural Potential Sensing

Abstract

Neurological functional electrical stimulation (NFES) provides a well-controlled and high degree of reconfigurability amount for producing the desired stimulation effect. For evaluating the effect of stimulation, the evoked potentials can be sensed. However, in practice, the unbalanced charge accumulation leads to residual charges and toxic electrochemical reactions at the electrode-tissue sensing interface, which causes electrode corrosion and tissue damage. This letter presents a twin compensation loop (TCL) charge-balancing (CB) topology for the NFES. The TCL-CB consists of two compensation loops, including a positive compensation loop (PCL) and a negative compensation loop (NCL). The PCL and NCL continuously detect and compensate for the accumulated negative and positive charges at the output of the Wilson current mirror (WSC), respectively. The circuits are targeted at integrated circuit (IC) realization, designed and fabricated in a 0.18-μm complementary metal oxide semiconductor (CMOS) technology. The power consumption of the WSC with TCL-CB is circa 79.2 μW and occupies a die area of 0.047 mm² (0.265 μm × 0.18 μm). Benefiting from TCL-CB, the charge mismatch at the output of WSC is reduced to less than 1%.