Design of a Programmable Passive SoC for Biomedical Applications Using RFID ISO 15693/NFC5 Interface

Abstract

Low power, low cost inductively powered passive biotelemetry system involving fully customized RFID/NFC interface base SoC has gained popularity in the last decades. However, most of the SoCs developed are application specific and lacks either on-chip computational or sensor readout capability. In this paper, we present design details of a programmable passive SoC in compliance with ISO 15693/NFC5 standard for biomedical applications. The integrated system consists of a 32-bit microcontroller, a sensor readout circuit, a 12-bit SAR type ADC, 16 kB RAM, 16 kB ROM and other digital peripherals. The design is implemented in a 0.18 µm CMOS technology and used a die area of 1.52 mm × 3.24 mm. The simulated maximum power consumption of the analog block is 592 µW. The number of external components required by the SoC is limited to an external memory device, sensors, antenna and some passive components. The external memory device contains the application specific firmware. Based on the application, the firmware can be modified accordingly. The SoC design is suitable for medical implants to measure physiological parameters like temperature, pressure or ECG. As an application example, the authors have proposed a bioimplant to measure arterial blood pressure for patients suffering from Peripheral Artery Disease (PAD).

An Ultra-Low-Power RFID/NFC Frontend IC Using 0.18 μm CMOS Technology for Passive Tag Applications

“…Figure 18 shows the micro-photograph of the fabricated IC where nearly 40% of the die area is left unused. Additional circuitries like analog to digital converters and sensor interface circuits can be accommodated in the unused die area as mentioned in [ 65 ]. For a supply voltage of , the digital core and input-output consumes and respectively, which is measured directly from the IC by using an external power source.…”

“…The fundamentals of the LDO are well presented in [ 61 , 62 , 63 , 64 ]. A comprehensive explanation of an LDO is illustrated by the authors in [ 65 ], in this paper only the critical parameters are presented.…”

Successive Approximation Register Analog-to-Digital Converter (SAR ADC) for Biomedical Applications

“…Where the charge injection is defned as the charge that exists between the source and drain terminals when the sample switch is turned of, and the clock feed through is defned as the charge injected due to the overlapping coupling capacitor between the gate and drain terminals. Consequently, it is preferable to implement the sample switch by using CMOS transmission gates [8,64,103] or the bootstrap switch in Figure 4 [2,5,6,11,17,22,24,31,34,45,53,58,63,65 Te variations in conductivity are reduced by utilizing the CMOS transmission gates, but the problem of input dependence still exists. Additionally, a large parasitic capacitor that limits the resolution of SAR appears.…”

“…ADC for wireless biomedical applications [2] must have low power consumption for a long battery lifetime. Also, the applications of biomedical impose extra requirements on ADC to have a smaller chip area, medium resolution, and sampling speed ranging from a few KS/s to a few MS/s [7,8].…”