title: A MEMS Interface IC With Low-Power and Wide-Range Frequency-to-Voltage Converter for Biomedical Applications.
abstract: This paper presents an interface circuit for capacitive and inductive MEMS biosensors using an oscillator and a charge pump based frequency-to-voltage converter. Frequency modulation using a differential crossed coupled oscillator is adopted to sense capacitive and inductive changes. The frequency-to-voltage converter is designed with a negative feedback system and external controlling parameters to adjust the sensitivity, dynamic range, and nominal point for the measurement. The sensitivity of the frequency-to-voltage converter is from 13.28 to 35.96 mV/MHz depending on external voltage and charging current. The sensitivity ranges of the capacitive and inductive interface circuit are 17.08 to 54.4 mV/pF and 32.11 to 82.88 mV/mH, respectively. A capacitive MEMS based pH sensor is also connected with the interface circuit to measure the high acidic gastric acid throughout the digestive tract. The sensitivity for pH from 1 to 3 is 191.4 mV/pH with 550 μV(pp) noise. The readout circuit is designed and fabricated using the UMC 0.18 μm CMOS technology. It occupies an area of 0.18 mm (2) and consumes 11.8 mW.
authors.forename: Md Shamsul
authors.initials: MS
authors.lastname: Arefin
authors.forename: Jean-Michel
authors.initials: JM
authors.lastname: Redouté
authors.forename: Mehmet Rasit
authors.initials: MR
authors.lastname: Yuce
mesh_terms: D000465:Algorithms; D015374:Biosensing Techniques / Q000295:instrumentation*; D025802:Electric Capacitance; D004867:Equipment Design; D055617:Micro-Electrical-Mechanical Systems / Q000295:instrumentation*