A low-power wireless nano-potentiostat for biomedical applications with ISO 18000-3 interface in 0.35 μm CMOS

A New Configurable Wireless Sensor System for Biomedical Applications with ISO 18000-3 Interface in 0.35 µm CMOS

“…Sensor values and other digital data, such as status information from a potentiostat, are transmitted to the reader by modulating the RF field. The transponder includes the following blocks [6]:Voltage rectifier with load modulator and limiting circuitry;Voltage regulator with bandgap reference;POR;Demodulator and clock recovery circuit;SPI interface.…”

“…A temperature independent bandgap voltage acts as reference. In general, the regulated voltage shows a temperature coefficient of −200 ppm/K [6]. Two voltage regulators are used to separate the noise of digital switching from the analog signal processing part: one for analog units (2.6 V) and one for digital circuits (1.8 V).…”

“…The digital part [6] of the transponder ASIC handles the protocol execution and the communication with the external sensor system. The minimum set of mandatory commands defined in ISO 18000-3 MODE 1 (respectively ISO/IEC 15693) [5] has been implemented to ensure compliance with standard readers.…”

“…It performs measurements and digital conversion including calibration and linearization of the sensor signal. It contains the following components [6]:A temperature sensor and a supply voltage measuring circuit;A cyclic ADC with 12 bit resolution and low power consumption;A digital to analog converter (DAC) with 6 bit resolution;A precision operational amplifier as control for the excitation voltage;A TIA for converting the current between the work electrode (WE) and the counter electrode (CE) into a corresponding voltage;A state machine for the ADC and measurement sequence timing;Dedicated registers for storage and transfer of measurement results;A serial EEPROM for storing chip ID, sensor offset/gain and simple calibration constants, e.g., for setting the control voltage and gain at the transimpedance amplifier;A charge pump for in-circuit programming of the EEPROM;An SPI slave interface for communication with the RF frontend;A POR circuit.…”

“…The composite architecture was chosen to ensure the reuse of the developed communication interface in other biomedical applications and to provide the possibility of combining several measuring sensors with one communication interface [6] which makes the system expandable and configurable. The biochemical sensor interface (potentiostat) presented in this article includes an amperometric measuring circuit and, a digital part including an EEPROM, and a SPI slave interface.…”