A charge-pump based multi-mode stimuli generator for cardiac pacemaking

A multi-mode charge pump based stimulator for cardiac pacemaking is presented. This system operates both as voltage-mode and charge-mode stimulator and can deliver voltage stimulus to the tissue with an arbitrary waveform. The core of the stimulator is a reconflgurable 3-stage charge pump circuit with variable switching frequency allowing to adjust the stimulus level to the desired value in a wide range. Two output stage switches control the connection of the charge pump to the load and determine the stimulation mode. If the charge pump output is always connected to the load, the voltage-mode stimulation will be realized whereas in the charge-mode stimulation, first a capacitor is charged to a specific voltage by the charge pump and then the controlled amount of charge is injected from the capacitor to the load while the charge pump has been disconnected. The measurements performed making use of a prototype PCB show that the systems can inject charge to the load in the range of 5 to 29 nC in the charge-mode and generates voltage pulses with the amplitude varies between 2.63 and 11.4 V in the voltage-mode stimulation. The stimulator efficiency varies from 65 to 90% for different output voltage stimulation levels.