2023 article
A Wireless Multimodal Physiological Monitoring ASIC for Injectable Implants
IEEE 49TH EUROPEAN SOLID STATE CIRCUITS CONFERENCE, ESSCIRC 2023, pp. 305–308.
This paper presents a wireless multimodal physiological monitoring ASIC fabricated in a CMOS 180 nm process. The application-specific integrated circuit (ASIC) is sized to be within the form factor of an injectable microchip implant and can measure electrocardiography (ECG), photoplethysmography (PPG), and body temperature. The low-power circuit design enables the ASIC to wirelessly receive the required power, 155.3 μW on average, via an inductive link. The ECG analog frontend (AFE) has input-referred noise (IRN) of 3.1 μVrms within 0. 3-1kHz. To measure PPG, the LED driver employs a switched-capacitor-based architecture as an energy-efficient and safe method to deliver current pulses in milliampere order to an LED. An integrator-based AFE amplifies the photodetector (PD) current with 47 pArms IRN within 0.1-10 Hz. Recorded physiological signals are digitized by a 10-bit successive approximation register (SAR) analog-to-digital converter (ADC) with an 8.79-bit effective number of bits (ENOB), followed by a backscatter-based data telemetry, which transmits data via intermediate-frequency (IF)-assisted load shift keying (LSK) modulation. The overall ASIC performance has been evaluated in vivo on anesthetized rats.