A 180 nm CMOS Integrated Optoelectronic Sensing System for Biomedical Applications

Abstract

This paper reports on a CMOS fully integrated optoelectronic sensing system composed of a Si photodiode and a transimpedance amplifier acting as the electronic analog front-end for the conditioning of the photocurrent generated by the photodiode. The proposed device has been specifically designed and fabricated for wearable/portable/implantable biomedical applications. The massive employment of sensor systems in different industrial and medical fields requires the development of small sensing devices that, together with suitable electronic analog front ends, must be designed to be integrated into proper standard CMOS technologies. Concerning biomedical applications, these devices must be as small as possible, making them non-invasive, comfortable tools for patients and operating with a reduced supply voltage and power consumption. In this sense, optoelectronic solutions composed of a semiconductor light source and a photodiode fulfill these requirements while also ensuring high compatibility with biological tissues. The reported optoelectronic sensing system is implemented and fabricated in TSMC 180 nm integrated CMOS technology and combines a Si photodiode based on a PNP junction with a Si area of 0.01 mm2 and a transimpedance amplifier designed at a transistor level requiring a Si area of 0.002 mm2 capable to manage up to nanoampere input currents generated by the photodiode. The transimpedance amplifier is powered at a 1.8 V single supply showing a maximum power consumption of about 54 μW, providing a high transimpedance gain that is tunable up to 123 dBΩ with an associated bandwidth of about 500 kHz. The paper reports on both the working principle of the developed ASIC and the experimental measurements for its full electrical and optoelectronic characterizations. Moreover, as case-examples of biomedical applications, the proposed integrated sensing system has also been validated through the optical detection of emulated standard electrocardiography and photoplethysmography signal patterns.

Survey of near-field wireless communication and power transfer for biomedical implants

“…In general, WPT techniques can be classified as radiative or non-radiative. Non-radiative approaches include inductive coupling [45], capacitive coupling [46], and magnetic resonance coupling [47].…”

A 6 Mbps 7 pJ/bit CMOS Integrated Wireless Simultaneous Lightwave Information and Power Transfer System for Biomedical Implants

“…Specific modules allow for the coding process and drive a semiconductor laser to optically transmit data and transfer power to the SLIPT internal unit. The latter operates as a data receiver and includes: (i) an Optical Wireless Power Transfer (OWPT) module with an integrated array of eight Si photodiodes that, once illuminated, generates the photocurrent to power the SLIPT internal unit circuitries [25,26]; (ii) an RX-READY block that enables the SLIPT external unit to transmit data only when the SLIPT internal unit is fully powered by the OWPT module; and (iii) an RX receiver module implementing the clock and data decoding process. To achieve the correct operation of the SLIPT system (i.e., data transmission/reception and optical power transfer), a pulse generator module is included in the external unit, which generates pulsed coded data by using a novel modulation technique that is the reversed version of the optical Synchronized Pulse Position Modulation (S-PPM) technique [27][28][29][30].…”