A 370-nW Bio-AFE With 2.9-μ Vrms Input Noise in an Octa-Channel System-in-Package for Multimode Bio-Signal Acquisition

A fully integrated and reconfigurable octa-channel bio-signal acquisition system-in-package (SiP), which enables the wireless measurement of electromyography (EMG), electrocardiogram (ECG), or electroencephalography (EEG), is presented in this article. Each chiplet contains an analog front end in combination with a channel-selection multiplexer, a successive-approximation-register analog–digital converter (SAR-ADC), an ultra-wideband transmitter (UWB-TX), a low-power on-chip crystal-based clock generation circuit, and a low-dropout voltage regulator, including voltage reference. The die occupies an area of 3.64 mm 2 in a 180-nm 1P6M CMOS technology. A flexible acquisition of bio-potentials is possible due to the rail-to-rail (R–R) input dc tolerance and multiple bandwidth and gain modes (0.2–128/512/2048 Hz, and 19.9–53.1 dB, respectively). In addition, a low total harmonic distortion (THD) of <tex-math notation="LaTeX">$-51.1$</tex-math> dB of the bio-signal acquisition analog front end (Bio-AFE) for bio-signal relevant levels and a high signal-to-noise-and-distortion ratio (SNDR) of 83.0 dB of the SAR-ADC result in a high linearity of the recorded bio-signals. A low input-referred noise ranging from 2.9 to 7.1 <tex-math notation="LaTeX">μ</tex-math> Vrms, together with a high differential input impedance of 216 M <tex-math notation="LaTeX">Ω</tex-math> and a common-mode rejection ratio (CMRR) of 81.6 dB, is essential for the acquisition of the low-amplitude bio-signals. The low-power consumption of 0.37–1 <tex-math notation="LaTeX">μ</tex-math> W per channel (mode-dependent) of the Bio-AFE and that of 1.22 <tex-math notation="LaTeX">μ</tex-math> W per channel of the SAR-ADC, both from a 1-V supply, enable battery-or RF-powered applications in a small form factor.