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A low-power switched-capacitor third-order sigma- delta (ΣΔ) modulator suitable for portable sensor systems is described. The architecture uses only one operational amplifier working in a time-interleaved fashion. The architecture employs swing reduction techniques to limit the swing and the slew-rate requirements of all internal nodes. Realized in a 0.18-μm 2P6M CMOS technology, the modulator provides 84-dB SNDR and 88-dB dynamic range in a signal bandwidth of 100 kHz and clock at 3.2 MHz. The 1.5-V supplied prototype dissipates 140 μW with a FoM of 54 fJ/conversion-level.
Date of Publication: Sept. 2012