An ASIC Interface for CMUTs-based Biosensors with High Voltage Boosting and Oscillator

With rapid development of Internet of Things, there is high demand for miniaturized biochemical sensors, which enable a digital-controlled connection and portable integration. In this work, we report an ASIC interface for capacitive micromachined ultrasonic transducers (CMUTs), offering multi-channel monitoring of frequency shifts and supplying high-voltage (HV) source. Previously reported CMUTs-based biochemical sensors required a peripheral power source to provide a DC driving voltage (e.g.,10-50 V), which was higher than the common circuit supply (e.g., 1.2-5 V). This resulted in additional circuit footprints and parasitic effects, especially for high frequency. Instead, we proposed an ASIC interface designed through TSMC 0.18-mu{m} HV BCD process with a die size of 2×2 mm2. Four-channel oscillators are proposed to track frequency shifts of CMUT resonators with a resonant frequency of 1.8MHz, and a start-up period up to 100 mu s and a phase noise of-38.73dBc/Hz at low offset of 100 Hz were observed, while consuming an average total power of 142.12 mu mathrm{W} in continuous mode. A PMOS-based HV charge pump is presented to generate a voltage boosting of 50 V with a 1.8-V input source, which enables tuning clock signals by implementing four-parallel ring oscillators with the frequency of 20-50 MHz. The proposed ASIC integrated with CMUTs is a molecules.