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.

[1]  Mohamad Sawan,et al.  New low-power low-voltage high-CMRR CMOS instrumentation amplifier , 1999, ISCAS'99. Proceedings of the 1999 IEEE International Symposium on Circuits and Systems VLSI (Cat. No.99CH36349).

[2]  Ramon Pallàs-Areny,et al.  Error analysis in two-terminal impedance measurements with residual correction , 2005, IEEE Transactions on Instrumentation and Measurement.

[3]  Keiichiro Kagawa,et al.  CMOS retinal prosthesis with on-chip electrode impedance measurement , 2004 .

[4]  Yin Chang,et al.  An Efficient Micro-Stimulator Array Using Unitary-Size DAC With Adiabatic Baseband Scheme , 2006, 2006 13th IEEE International Conference on Electronics, Circuits and Systems.

[5]  Yin Chang,et al.  Design And Implementation Of A Monolithic Programme-Controlled System For Retinal Prosthesis , 2006, 2006 13th IEEE International Conference on Electronics, Circuits and Systems.

[6]  T. Nirschl,et al.  Yield and speed optimization of a latch-type voltage sense amplifier , 2004, IEEE Journal of Solid-State Circuits.

[7]  Liberson Wt,et al.  Functional electrotherapy: stimulation of the peroneal nerve synchronized with the swing phase of the gait of hemiplegic patients. , 1961, Archives of physical medicine and rehabilitation.

[8]  R.J. Greenberg,et al.  Stimulus induced pH changes in retinal implants , 2004, The 26th Annual International Conference of the IEEE Engineering in Medicine and Biology Society.

[9]  Arantxa Uranga,et al.  Electrode–Tissue Impedance Measurement CMOS ASIC for Functional Electrical Stimulation Neuroprostheses , 2007, IEEE Transactions on Instrumentation and Measurement.

[10]  J. Weiland,et al.  Perceptual thresholds and electrode impedance in three retinal prosthesis subjects , 2005, IEEE Transactions on Neural Systems and Rehabilitation Engineering.