A High-Voltage Output Driver for Implantable Biomedical Stimulators and I/O Applications

This work presents a high voltage output driver stage for implantable microelectronic stimulators implemented in AMI 1.5-μm standard CMOS technology. Stacked device topology is used to implement a high voltage output driver capable of delivering output voltages up to three times the nominal supply voltage. Oxide stress and hot carrier effects are minimized as the voltage across any two terminals of all devices in the output stage are kept below the nominal supply voltage for the utilized technology. Novel techniques are used for level shifting and delay equalization of the complementary inputs to the output driver. The unloaded driver has negligible static power consumption. The output stage is capable of delivering 8.6 V output with a 9 V supply to a 1 kΩ load at an operating frequency of 100 kHz. This corresponds to a driver efficiency of 95.6%. Further improvements and experiments are underway.