Low-power low-voltage current readout circuit for inductively powered implant system

Area of Science:

• Electrical Engineering
• Biomedical Engineering
• Integrated Circuit Design

Background:

• Biomedical sensor instrumentation requires low voltage and low power for on-chip wireless power and data telemetry.
• Batteryless operation and wireless telemetry are crucial for robust, reliable, and long-lasting implantable units.

Purpose of the Study:

• To demonstrate a low-power, low-voltage sensor readout circuit powered by an inductive link for biomedical applications.
• To present two versions of CMOS-fabricated readout circuits capable of detecting sensor currents and generating frequency-proportional square-wave data signals.

Main Methods:

• Designed and fabricated two versions of sensor readout circuits using bulk complementary metal-oxide semiconductor (CMOS) processes (0.35-μm and 0.5-μm).
• Characterized circuit performance, including power consumption, operating voltage, and data signal generation (Amplitude-Shift Keying and Frequency-Shift Keying) for sensor currents from 0.2 μA to 2 μA.

Main Results:

• The 0.35-μm CMOS circuit (ASK) operates at 1.5-V, consumes 400 μW, and outputs 76 Hz to 500 Hz.
• The 0.5-μm CMOS circuit (FSK) operates at 2.5-V, consumes 1.675 mW, and outputs 1 kHz to 9 kHz.
• Measurement results confirmed the functionality of both prototype circuits.

Conclusions:

• Both prototype circuits successfully detect sensor currents and generate frequency-modulated square-wave data signals.
• These low-power, low-voltage circuits are suitable for batteryless, wireless biomedical sensor systems.
• Potential applications include monitoring blood glucose, lactate, pH, and oxygen levels in physiological systems.