A Power optimized switched-capacitor based approach in voltage-controlled cardiac stimulation

Voltage-mode implantable medical stimulators employ either high-voltage digital-to-analog converters (DACs) or high-voltage drivers to produce pulse stimulations in low power implantable medical applications. In this paper, a new design method for voltage-mode stimulation with variable efficiency is proposed. This method eliminates the high-voltage driver or DAC and replaces them with a series combination of a low-voltage DAC and a high-voltage charge pump circuit. The stimulation amplitude can be varied by changing the input digital code of the DAC and the switching frequency of the charge pump. A comprehensive analysis subjected to the design constraints is presented to find the minimum acceptable values of the DAC resolution and the charge pump switching frequency for minimizing the power consumption and improving the overall efficacy of the stimulation pulses. The SPICE simulations are presented to examine the credibility and accuracy of the derived equations and the operation of the proposed circuits.