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.