A 64-Channel sub-1nC Charge-balanced Stimulator IC for Seizure Suppression

Abstract

We present a 64-channel implantable neural stimulator with sub-nC charge balanced current stimulation for seizure suppression applications. The regulated cascode current driver achieves almost full VDD compliance voltage range. A passive charge balancing by shorting working and reference electrodes with a bootstrapped switch keeps the residual charge level within a safe limit, enabling faster-switching operation. The stimulation parameters, such as current pulse width, channel activation, activation frequency, and current amplitude, are highly reconfigurable and adjusted through the SPI interface. Significantly, the current amplitude can be varied from 1μA to 1.8 mA. As a result, the proposed neural stimulator fabricated with a 0.18μm standard CMOS process effectively suppresses seizures within a safe limit with a residual charge of less than 1nC through the in-vivo test.