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This paper presents an ultra-low power incremental ADC for biosensor interface circuits.The ADC consists of a resettable second-order delta–sigma(△Σ) modulator core and a resettable decimation filter.Several techniques are adopted to minimize its power consumption.A feedforward path is introduced to the modulator core to relax the signal swing and linearity requirement of the integrators.A correlated-double-sampling(CDS)technique is applied to reject the offset and 1/f noise,thereby removing the integrator leakage and relaxing the gain requirement of the OTA.A simple double-tailed inverter-based fully differential OTA using a thick-oxide CMOS is proposed to operate in the subthreshold region to fulfill both an ultra-low power and a large output swing at 1.2V supply.The signal addition before the comparator in the feedforward architecture is performed in the current domain instead of the voltage domain to minimize the capacitive load to the integrators.The capacitors used in this design are of customized metal–oxide–metal(MOM) type to reach the minimum capacitance set by the k T =C noise limit.Fabricated with a 1P6 M 0.18m CMOS technology,the presented incremental ADC consumes600nW at 2kS/s from a 1.2V supply,and achieves 68.3dB signal to noise and distortion ratio(SNDR) at the Nyquist frequency and an FOM of 0.14 p J/conversion step.The core area is 100120 m2.
This paper presents an ultra-low power incremental ADC for biosensor interface circuits. The ADC consists of a resettable second-order delta-sigma (ΔΣ) modulator core and a resettable decimation filter. Severral techniques are adopted to minimize its power consumption .A feedforward path is introduced to the modulator core to relax the signal swing and linearity requirement of the integrators. A correlated-double-sampling (CDS) technique is applied to reject the offset and 1 / f noise, gain requirement of the OTA. A simple double-tailed inverter-based fully differential OTA using a thick-oxide CMOS is proposed to operate in the subthreshold region to fulfill both an ultra-low power and a large output swing at 1.2V supply. signal addition before before the comparator in the feedforward architecture is performed in the current domain instead of the voltage domain to minimize the capacitive load to the integrators. esign are of customized metal-oxide-metal (MOM) type to reach the minimum capacitance set by k T = C noise limit. Fabrication with a 1P6 M 0.18m CMOS technology, presented incremental ADC consumes 600nW at 2kS / s from a 1.2 V supply, and achieves 68.3dB signal to noise and distortion ratio (SNDR) at the Nyquist frequency and an FOM of 0.14 pJ / conversion step. The core area is 100120 m2.