A safe MOSFET driver for stimulation of biological tissue

Safety is one of the main concerns in ASICs for implantable medical devices. One general rule for safety is that the failure of a single circuit element in a circuit connected to tissue must not cause a DC current flow through the electrode connected to tissue larger than a few μA. In single electrodes and electrode arrays, there are many switches to deliver stimuli, to select the polarity, or to select the output electrode, etc., that are potentially harmful for example in the case of a punctured MOS switch gate. In this work the design, simulation, and test of a novel safe switch gate control circuit block is presented. The circuit was fabricated in a 0.6μm SOI HV technology, and is aimed at driving MOSFETs in direct contact to biological tissue to drive up to 18V stimuli.