A 0.5V, 6.2$μ$W, 0.059mm$^{2}$ Sinusoidal Current Generator IC with 0.088% THD for Bio-Impedance Sensing

TL;DR

A half-period (HP) reset is introduced in the capacitive DAC, leading to around 30dB reduction of in-band noise by avoiding the sampling of data-dependent glitches and attenuating the kT/C noise and the non-idealities of reset switches (SW).

Abstract

This paper presents the first sub-10$μ$W, sub-0.1% total harmonic distortion (THD) sinusoidal current generator (CG) integrated circuit (IC) that is capable of 20kHz output for the bio-impedance (Bio-Z) sensing applications. To benefit from the ultra-low-power nature of near-threshold operation, a 9b pseudo-sine lookup table (LUT) is 3b $ΔΣ$ modulated in the digital domain, thus linearity burden of the digital-to-analog converter (DAC) is avoided and only a 1.29$μ$W of logic power is consumed, from a 0.5V supply and a 2.56MHz clock frequency. A half-period (HP) reset is introduced in the capacitive DAC, leading to around 30dB reduction of in-band noise by avoiding the sampling of data-dependent glitches and attenuating the kT/C noise and the non-idealities of reset switches (SW).

Figures (8)

• Figure 1: Overall architecture of the sinusoidal CG IC.
• Figure 2: HP reset.
• Figure 3: Simulated spectrum of the HP reset scheme.
• Figure 4: Chip photograph and the photograph of the same chip without top 3 layers (right).
• Figure 5: Measured spectrum of the CG and the DAC output.