1.4V 13μW 83dB DR CT-ΣΔ modulator with Dual-Slope quantizer and PWM DAC for biopotential signal acquisition

High-resolution Sigma-Delta (∑Δ) ADCs are increasingly used in portable medical applications for the measurement of biopotential signals. This paper presents the implementation and measurements of a novel ultra-low power low voltage multi-bit continuous-time sigma-delta (CT-∑Δ) modulator, whose quantizer and feedback DACs operate in the time domain. Instead of the conventional flash quantizer and mismatch corrected multi-bit feedback DACs, a Dual-Slope (DS) quantizer and a Pulse-Width Modulated (PWM) DACs have been adopted in this design. The modulator has been implemented in a standard 0.18μm CMOS technology and features 83dB dynamic-range (DR) for a signal bandwidth of 256Hz. When clocked at 917kHz it consumes 13.3μW from a 1.4V supply.