Abstract-As new functionality is added to the implantable devices, their power requirements also increase. Such power requirements make it hard for keeping such implants operational for long periods by non-rechargeable batteries. This result in a need for frequent surgeries to replace these batteries. Rechargeable batteries can satisfy the long-term power requirements of these new functions. To minimize the discomfort to the patients, the recharging of the batteries should be as infrequent as possible. Traditional battery charging methods have low battery charging efficiency. This means they may limit the amount of charge that can be delivered to the device, speeding up the depletion of the battery and forcing frequent recharging. In this paper, we evaluate the suitability of a state-of-theart general purpose charging method called current-pumped battery charger (CPBC) for implant applications. Using offthe-shelf components and with minimum optimization, we prototyped a proof-of-concept transcutaenous battery charger based on CPBC and show that the CPBC can charge a 100 mAh battery transcutaneously within 137 minutes with at most 2.1• C increase in tissue temperature even with a misalignment of 1.3 cm in between the coils, while keeping the battery charging efficiency at 85%.
In neural implants, an analog-to-digital converter (ADC) provides the delicate interface between the analog signals generated by neurological processes and the digital signal processor that is tasked to interpret these signals for instance for epileptic seizure detection or limb control. In this paper, we propose a low-power ADC architecture for neural implants that process extracellular potentials. The proposed architecture uses the spike detector that is readily available on most of these implants in a closed-loop with an ADC. The spike detector determines whether the current input signal is part of a spike or it is part of noise to adaptively determine the instantaneous sampling rate of the ADC. The proposed architecture can reduce the power consumption of a traditional ADC by 62% when sampling extracellular potentials without any significant impact on spike detection accuracy.
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