Novel 10-Bit Impedance-to-Digital Converter for Electrochemical Impedance Spectroscopy Measurements

Area of Science:

• Electrical Engineering
• Biomedical Engineering
• Analytical Chemistry

Background:

• Electrochemical impedance spectroscopy (EIS) is a crucial technique for analyzing chemical and biological systems.
• Existing EIS systems often require complex signal processing and bulky components.
• There is a need for integrated, high-performance solutions for EIS measurements.

Purpose of the Study:

• To propose and validate a novel 10-bit impedance-to-digital converter (IDC) for EIS measurement systems.
• To design and fabricate a compact IDC chip capable of directly converting impedance magnitude and phase to digital codes.
• To demonstrate the functionality of the IDC within a complete EIS measurement system.

Main Methods:

• Design and fabrication of a 10-bit IDC using a 0.35 μm 2P4M mixed-signal polycide process.
• The IDC comprises a magnitude-to-digital converter (MDC) and a phase-to-digital converter (PDC).
• Fabricated chip core area is 0.07 mm² and operates from 0.1 mHz to 100 kHz.

Main Results:

• The fabricated IDC chip exhibits excellent accuracy over a wide frequency range.
• Measured differential nonlinearity (DNL) for the MDC is within -0.3/+0.3 least significant bit (LSB).
• Measured integral nonlinearity (INL) for the MDC is approximately -3/+1 LSB.

Conclusions:

• The proposed 10-bit IDC offers a compact and accurate solution for EIS measurement systems.
• The integrated IDC chip simplifies EIS data acquisition and processing.
• Validation with ZoBell's and melatonin solutions confirms the IDC's functional performance in EIS applications.