A 168 dB FoM ISFET-Integrated CT Delta Sigma Frontend With Gm-Boosted Linearity and Hybrid Noise Shaping Achieving...

Area of Science:

• Biomedical Engineering
• Integrated Circuit Design
• Sensor Technology

Background:

• Ion-selective field-effect transistors (ISFETs) are crucial for biochemical sensing.
• Existing ISFET frontends often face challenges with power efficiency and integration complexity.
• Continuous-time delta-sigma modulators (CT-ΔΣM) offer high resolution for analog-to-digital conversion.

Purpose of the Study:

• To present a low-power, ISFET-integrated frontend architecture.
• To improve energy efficiency by directly merging the ISFET with the CT-ΔΣM.
• To enhance the performance of biochemical sensing systems.

Main Methods:

• Direct integration of ISFET as both sensor and integrator input stage.
• Utilizing a G_m-C based CT-ΔΣM architecture.
• Incorporating a passive low-pass filter DAC (LPF-DAC) for noise shaping.
• Employing source degeneration and gm-boost techniques for linearity.

Main Results:

• Achieved a peak Signal-to-Noise and Distortion Ratio (SNDR) of 84.2 dB.
• Measured a dynamic range of 90.4 dB over a 10 kHz bandwidth.
• Demonstrated ultra-low power consumption of 41.5 µW.
• Obtained a Schreier Figure of Merit (FoM) of 168 dB, an 8 dB improvement.
• Exhibited an averaged sensitivity of 29.04 mV/pH and a resolution of 6.8 m-pH.

Conclusions:

• The proposed ISFET-integrated CT-ΔΣM frontend offers superior performance and energy efficiency.
• The architecture is well-suited for low-power, high-accuracy biochemical sensing applications.
• This design represents a significant advancement over previous ISFET frontend solutions.