A 379nW 58.5dB SNDR VCO-based ΔΣ modulator for bio-potential monitoring

A VCO-based delta-sigma modulator (ΔΣM) is proposed for bio-potential signal acquisition. The VCO quantizer is placed in a loop with 1-bit feedback to improve modulator linearity. Furthermore, frequency calibration employing gated VCO technique is proposed to improve the operation range. Fabricated in a 0.18μm CMOS, this chip consumes 379nW and occupies an active area of 0.06mm2. Over a 2kHz signal bandwidth, the proposed ΔΣM achieves a peak SNDR of 58.5dB, which results in an FoM of 137fJ/conv.-step.

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