Researches And Designs Of Wireless Switched-capacitor Stimulation(SCS) System For DBS

For a long history,for motility disorders,epilepsy,Parkinson's and other neurological disease usually rely on drug therapy and non-drug therapy.Both solutions were proved to be effective,but they are not so1 popular for the clinical application because of some drawbacks.In recent years,with the development of microelectronics technology,implantable medical devices become more popular.The clinical practice has already been proved that implantable devices has much less injury to human body and much less syndrome and is reversible,but the tradition medical devices need to implant primary battery with large volume into the chest for power supply,it is very difficulty for surgery operation and machinery production.Therefore,the design of implantable medical devices with a wireless transmission,low power consumption,high security and strong system control is particularly important.Based on the collected documents,the electrical stimulation mechanism and the development situation of DBS technique are concluded in this paper.And based on several DBS device structure and working principle,we analyzed the key technologies in DBS system design,which includes:supply technology,capacitor charging and charge balance,energy efficient technology and so on.Considering the microminiaturization and energy-efficient requirements in the DBS design,a deep brain switched-capacitor stimulation,which is based on wireless energy transmission is discussed in this paper.The feasibility is also discussed in detail.The SCS system is composed of in vitro which is control part and in vivo stimulation,we mainly discuss the in vivo part in this paper.The circuit system mainly includes:power management module? the capacitance charging module,the capacitance charging control module,charge management module?channel selection module,discharge polarity selection module and the quantity of discharge capacitance selection module.Compared with several other stimulator structure,the deep brain switched-capacitor stimulation can directly received power from the secondary coil and for storage capacitor charging,greatly improve the stimulator's efficiency.Besides,the current pulse of stimulator generate is exponential decay pulse,compared to others kinds of stimulation waveform,the exponential decay wave can activate nervous tissue more effectively under the same energy.In order to improve safety coefficient,this system adopts charge detection module to control the quantity of positive and negative charges that sent to the nervous tissue,eliminate the charge accumulation in thetissues.The design circuit system was based on a TSMC 0.35?m 1-poly 6-metal mixed signal CMOS process,using Cadence-spectre for circuit stimulation,demonstrating the feasibility of the various modules and system.Stimulation results show that,the stimulator work stable under the 13.56 MHz AC input case,and the voltage of positive and negative capacitor can reach ±1.2V,respectively,and can be adjustable in 16 levels.The maximum amplitude of stimulated current in the electrode is 5.04 mA which is adjustable in 64 levels.