A novel charge-metering method for voltage mode neural stimulation

This paper presents a novel, fully-integrated circuit for achieving change-balanced voltage-mode neural stimulation based on a charge-metering technique. The proposed system uses two small on-chip capacitors, a counter, two comparators and a control-logic circuit to measure the charge delivered to the tissue. This has been designed to deliver a maximum charge stimulus of 10.24 nC within 100 μs. Simulated results show a charge delivery error of 0.4-4% and a maximum residual charge of -73 pC. Implemented in 0.18 μm CMOS, the total power consumption is 42 μW.