An impedance measurement analog front end for wirelessly bioimplantable applications

This paper reports on design and implementation of an impedance measurement analog front end (AFE) for wirelessly powered medical electronic applications. Going through the literature on the implantable applications, it is understood that a common impedance value of 10 kΩ is agreed in terms of the human tissues. It is, however, also well known that such an impedance value could be varied toward 100 kΩ as a result of the variances in electrode-tissue interfacing, indicating internally physiological change or electrode failure. The variances in electrode-tissue interfacing also cause electrode with unequal charges in biphasic stimulation, damaging surrounding neurons. Proposed aims to overcome the potential problem, which is able to differentiate variances in impedance ranging from 10 kΩ to 100 kΩ. An impedance value exceeding 100 kΩ is considered electrode failure due to the malfunction of providing predefined current output in stimulator. The measured impedance can be backscattered to the external device through an integrated modulation technique.