A fully on-chip LDO voltage regulator with 37 dB PSRR at 1 MHz for remotely powered biomedical implants

This article presents a fully on-chip low-power LDO voltage regulator dedicated to remotely powered wireless cortical implants. This regulator is stable over the full range of alternating load current and provides fast load regulation achieved by applying a time-domain design methodology. Moreover, a new compensation technique is proposed and implemented to improve PSRR beyond the performance levels which can be obtained using the standard cascode compensation technique. Measurement results show that the regulator has a load regulation of 0.175 V/A, a line regulation of 0.024%, and a PSRR of 37 dB at 1MHz power carrier frequency. The output of the regulator settles within 10-bit accuracy of the nominal voltage (1.8 V) within 1.6μs, at full load transition. The total ground current including the bandgap reference circuit is 28μA and the active chip area measures 290μm×360μm in a 0.18μm CMOS technolog

Read Range Limitation in IF-Based Far-Field RFID Using ASK Backscatter Modulation

A model is proposed to describe the fundamental read range limitation due to the local oscillator phase noise in the reader, in IF-based, far-field RFID systems using amplitude-shift keying backscatter modulation. The relation between the system parameters (such as the data transfer rate) and the read range is discussed. The model is validated by measurements done on two different laboratory tag-reader systems

Area and Power Efficient Ultra-Wideband Transmitter Based on Active Inductor

This paper presents the design of an impulse radio ultra-wideband (IR-UWB) transmitter for low-power, short-range, and high-data rate applications such as high density neural recording interfaces. The IR-UWB transmitter pulses are generated by modulating the output of a local oscillator. The large area requirement of the spiral inductor in a conventional on-chip LC tank is overcome by replacing it with an active inductor topology. The circuit has been fabricated in a UMC CMOS 180 nm technology, with a die area of 0.012 mm2. The temporal width of the output waveform is determined by a pulse generator based on logic gates. The measured pulse is compliant with Federal Communications Commission (FCC) power spectral density limits and within the frequency band of 3-6 GHz. For the minimum pulse duration of 1 ns, the energy consumption of the design is 20 pJ per bit, while transmitting at a 200 Mbps data rate with an amplitude of 130 mV

Inductive Power Link for a Wireless Cortical Implant with Biocompatible Packaging

This article presents an inductive power link for a cortical implant. The link includes a Class-E power amplifier, an inductive link, a matching network, and a rectifier. The coils of the inductive link are designed and optimized for a distance of 10mm (scalp thickness). The power amplifier is designed in order to allow closed loop power control by controlling the supply voltage. A new packaging topology is proposed in order to position the implant in the skull, without occupying much area, but still obtaining short distance between the remote powering coils. The package is fabricated using biocompatible materials such as PDMS and Parylene-C, and it includes the secondary coil, the matching network, and the rectifier. The power efficiency of the link is characterized for a wide range of load power (1-20mW) and found to be 8.1% for nominal load of 10mW. The matching network improves the power efficiency on the whole range, compared to the link without the matching network

An Energy-Efficient Bridge-to-Digital Converter for Implantable Pressure Monitoring Systems

This paper presents an energy-efficient, duty-cycled, and spinning excitation bridge-to-digital converter (BDC) designed for implantable pressure sensing systems. The circuit provides the measure of the pulmonary artery pressure that is particularly relevant for the monitoring of heart failure and pulmonary hypertension patients. The BDC is made of a piezoresistive pressure sensor and a readout integrated circuit (IC) that comprises an instrumentation amplifier (IA) followed by an analog-to-digital converter (ADC). The proposed design spins both the bridge excitation and the ADC’s sampling input voltages simultaneously and exploits duty cycling to reduce the static power consumption of the bridge sensor and IA while cancelling the IA’s offset and 1/f noise at the same time. The readout IC has been designed and fabricated in a standard 180-nm CMOS process and achieves 8.4 effective number of bits (ENOB) at 1 kHz sampling rate while drawing 0.53 µA current from a 1.2 V supply. The BDC, built with the readout IC and a differential pressure sensor having 5 kΩ bridge resistances, achieves 0.44 mmHg resolution in a 270 mmHg pressure range at 1 ms conversion time. The current consumption of the bridge sensor by employing duty cycling is reduced by 99.8% thus becoming 0.39 µA from a 1.2 V supply. The total conversion energy of the pressure sensing system is 1.1 nJ, and achieves a figure-of-merit (FoM) of 3.3 pJ/conversion, which both represent the state of the art

Design methodology and comparison of rectifiers for UHF-band RFIDs

Rectifiers are important energy converters and henceforth crucial building blocks for RFID applications. In the first half of the work, we have presented a design methodology for matching the rectifier input impedance with the antenna to maximize the rectifier power conversion efficiency. The proposed design approach uses the fundamental transconductance (Gm(1)) analysis to estimate the rectifier input impedance. In the second half, a comparison between various possible single-stage rectifier topologies implemented in a CMOS 0.18 mu m technology operating at UHF-band is presented. Using voltage conversion efficiency as the FOM, the optimum rectifier topology for RFID application is determined

Fully Integrated Biochip Platforms for Advanced Healthcare

Recent advances in microelectronics and biosensors are enabling developments of innovative biochips for advanced healthcare by providing fully integrated platforms for continuous monitoring of a large set of human disease biomarkers. Continuous monitoring of several human metabolites can be addressed by using fully integrated and minimally invasive devices located in the sub-cutis, typically in the peritoneal region. This extends the techniques of continuous monitoring of glucose currently being pursued with diabetic patients. However, several issues have to be considered in order to succeed in developing fully integrated and minimally invasive implantable devices. These innovative devices require a high-degree of integration, minimal invasive surgery, long-term biocompatibility, security and privacy in data transmission, high reliability, high reproducibility, high specificity, low detection limit and high sensitivity. Recent advances in the field have already proposed possible solutions for several of these issues. The aim of the present paper is to present a broad spectrum of recent results and to propose future directions of development in order to obtain fully implantable systems for the continuous monitoring of the human metabolism in advanced healthcare applications

The Future of Intracranial EEG Recording in Epilepsy: a Technological Issue?

Intracranial EEG information used for epilepsy surgery has been provided from large widely spaced electrodes over a narrow bandwidth. However, over the last decades, research on animal and more recently on human, promoted by increased interest in developing high-density microelectrode arrays (MEA), has opened new windows for the comprehension of seizure origin and propagation at a submillimeter scale. From an electrophysiological perspective MEA demonstrate to be able to record local field potentials recordings and possibly single units in the mouse cortex. The limitations on the number of channels that can be recorded simultaneously may limit the number of microelectrodes that can be considered and consequently the extent of brain coverage. Thanks to improving microfabrication techniques, several prototypes of MEA are under development and investigation. They will certainly play an important role in the improvement of the understanding of the complicated and evolving concept of epileptogenesis and provide the development of new strategies regarding neurosurgical therapeutic issues