This paper proposes a dual-output Sample-and-Hold (SH) ultra low-power programmable voltage reference (SH-PVR). Our mixed-signal system regulates the ripple voltage on the output channels due to the leakage current, by monitoring the amplified ripple on a channel replica. The refresh frequency of the references is minimized for the minimum current consumption, while maintaining the ripple specification. Designed and implemented in TSMC 180-nm CMOS technology, the SH-PVR provides two references, with a programmability range [0.5 - 2]$\mathbf{V}$, and a step size of 50 mV. The system achieves a current consumption of 330 nA, with an output ripple below 10$\mu \mathbf{V}$, and it is suitable for ultra low-power devices for IoT, wearable, and implantable applications.

This paper proposes a novel architecture for the generation of a programmable voltage reference: the background-calibrated (BC)-PVR. Our mixed-signal architecture periodically calibrates a static ultra low-power voltage reference generator, from an accurate bandgap reference. The portion of the chip used for the calibration can be powered down with a programmable duty-cycle. The system aims to fully exploit the small temperature derivative vs time$D_{T}$of several application domains to minimize the average current consumption. The BC-PVR has been designed and implemented in TSMC 55-nm CMOS technology, and it achieves the largest reported programming reference output range [0.42 - 2.52] V, over the temperature range [−20, 85] °C. The duty-cycle mode allows nanoampere current consumption, and the large design flexibility permits to optimize the system performance for the specific application. These features make the BC-PVR very well-suited for power-constrained electronic systems.

Modern and miniaturized ASICs enable the development of anatomically constrained applications within the biomedical framework, such as smart contact lenses. Recent works report lenses receiving power and communicating through inductive coupled links. However, the efficiency of an inductive link depends highly on alignment and distance between coils, thus encouraging the exploration of other techniques to power and communicate a smart contact lens. Intra-body links emerge as an alternative to inductive ones for wearable devices, with promising path-loss results reported in previous works. Here, we evaluate the feasibility of powering a smart contact lens through an intra-body link. We propose a simplified 3D-FEM human-head model to estimate channel losses in a real contact lens situation. Then, we validate the pathloss estimations on the head through a human arm experiment, and comparison against a simplified 3D-FEM human-arm model. Based on our analysis, we estimate retrieved power of μW level, demonstrating the feasibility of using an intra-body link to power a smart contact lens.

This paper presents a digitally assisted tunable high pass filter for biomedical applications, implemented using unipolar a-IGZO TFTs manufactured on a flexible substrate. The proposed system is based on a master-slave approach. It takes advantage of the signal attenuation experienced in a high pass filter when a reference sinusoidal signal with a frequency lower than the cut off frequency is applied. The signal attenuation is monitored and a feedback loop automatically controls the small-signal resistance in the master and slave filters to obtain a specific signal attenuation, which in turn sets the passband frequency of the high pass filter. The presented approach is not only useful for setting a sub Hz cut off frequency but it is shown to be effective in counteracting parameter and supply voltage variations. The method presented in the paper can be also applied to Silicon biomedical circuits.