- Research Article
- 10.1109/lsens.2025.3649906
A Sub-1 V Resistance-to-Frequency Converter With High Sensitivity for Biomedical Interfaces
- Jan 01, 2026
- IEEE Sensors Letters
- Guljar Ansari + 3 more +3
This work presents a compact constant-current (CC)-based relaxation converter where the patch sensor produces a linear sensing voltage, enabling controlled and linear frequency variation through direct resistance-to-voltage mapping. Implemented in a 65 nm CMOS process, the design occupies 0.00897 mm <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$^{2}$</tex-math></inline-formula> and consumes optimum power of 3.24 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\mu$</tex-math></inline-formula> W at a 0.9 V supply, while operating reliably across 0.8-1.0 V. The sensitivity is 2.84 MHz/V at 0.9 V, decreasing by about 10% at 0.8 V and increasing by roughly 26 % at 1.0 V. Overall, the proposed converter delivers 5.5× higher sensitivity and improved power efficiency compared to conventional relaxation-oscillator interfaces. The measured oscillation range of 1.4-4.5 MHz with non-linearity error <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\pm$</tex-math></inline-formula>0.36 % which supports high-resolution, tunable operation suitable for biomedical and wearable sensing applications.
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