A Fully Integrated Current-Mode Continuous-Time Delta-Sigma Modulator for Biological Nanopore Read Out

Area of Science:

• Electrical Engineering
• Analog Integrated Circuit Design

Background:

• Traditional current-to-digital converters often require external anti-aliasing filters, increasing complexity and power consumption.
• Achieving low noise floors in current-mode converters is crucial for high-precision applications.

Purpose of the Study:

• To present a fully integrated, low-noise current-to-digital converter (CDC) utilizing current-mode continuous-time delta-sigma modulators (CT DSMs).
• To demonstrate the effectiveness of the CT DSM architecture in achieving high performance without external anti-aliasing filters.

Main Methods:

• The circuit was fabricated using a standard 0.35 μm CMOS process.
• Two feedback configurations were implemented: transistor-based and capacitor-based current division, to mitigate reference current noise.
• The CT DSM architecture inherently provides oversampling and anti-aliasing filtering.

Main Results:

• Achieved a noise floor as low as 200 fA_rms within a 10 kHz bandwidth.
• Demonstrated worst-case anti-aliasing filtering of -110 dB at 1.59 MHz, eliminating the need for external filters.
• The capacitor-based feedback version achieved a power consumption of 4.6 mW and an area of 0.32 mm².

Conclusions:

• The developed current-mode CT DSM-based CDC offers a highly integrated, low-noise solution with inherent anti-aliasing capabilities.
• The design significantly reduces complexity, area, and power consumption compared to traditional approaches.
• This work paves the way for more efficient and compact data acquisition systems.