A switched-mode multichannel neural stimulator with a minimum number of external components

This work proposes a system design for neural stimulators. It eliminates the need for a DC-DC converter which is normally used to increase the battery voltage. Instead it combines the DC-DC converter and stimulator output stage into a single system block. The number of external components needed for the system is reduced to a single inductor only. The system offers high power efficiency operation (theoretical power efficiency of 100% and a simulated efficiency of around 60% over the full output range) by employing switched-mode operation. Furthermore the output has a current source character, making charge balanced stimulation relatively easy to implement. Finally it is also possible to stimulate multiple channels independently with this system. An example design is presented that can stimulate two channels with a maximum output voltage of 10 V, while being powered from a 3.5V battery.