Andrea Rossini

A Clock-Less 10-bit Pipeline-Like A/D Converter for Self-Triggered Sensors

In this paper, a novel 10-bit A/D converter based on a pipeline-like architecture specific for low-noise, self-triggered sensors, (e.g., X-rays and 7-rays spectrometry) is presented. The main innovative feature of the proposed A/D structure is the concept that, for a sampled input signal, a pipeline ADC may behave as a combinatorial logic and may operate without any timing signal (clock). The conversion is obtained asynchronously propagating the partial conversions and the residues through the various stages. This concept is validated by means of a prototype ADC fabricated in a standard 0.35 mum CMOS technology. The active area is 2.24 mm2, and it provides a conversion in 2.5 mus (i.e., it can operate with a 400 kS/s data rate) featuring an ENOB equal to 8.91.

A Complete Read-Out Channel With Embedded Wilkinson A/D Converter for X-Ray Spectrometry

This paper presents a complete read-out channel suitable for large arrays of X-ray detectors to be used for spectrometry applications in space. The system is fully integrated except for the X-ray detector. It basically consists of a front-end circuit for processing the detector signal, a Wilkinson A/D converter for the analog-to-digital conversion and the digital logic required to ensure the correct handshaking between all the blocks of the read-out channel. The system allows us to process the signal provided by the detector down to the final analog-to-digital conversion. All these functionalities are embedded in a single chip that, in its final version, will be bump-bonded to the matrix of X-ray detectors. The chip, designed in a 0.35 mum CMOS technology, achieves an input-referred noise of 34 erms - , consuming 0.9 mW from a 3.3 V power supply. The on-board A/D converter features 10 bits of resolution with a maximum conversion time of 210 mus. The INL and DNL of the whole read-out channel are equal to plusmn3.3 LSB and plusmn0.2 LSB, respectively.

A 1.2 V sense amplifier for high-performance embeddable NOR flash memories

This paper presents a sense amplifier scheme for low-voltage embeddable NOR flash memory applications. The architecture of the proposed sense amplifier is based on a folded cascode configuration which allow the bit-line voltage to be regulated even in the case of a power supply of about 1.08 V. The proposed scheme was designed using low-leakage transistors for a 0.13-/spl mu/m flash CMOS technology. Simulation showed a read time of 16 ns and 11 ns for the worst-case and the best-case condition, respectively.

A 12.4 ENOB Incremental A/D Converter for High-Linearity Sensors Read-Out Applications

In this paper a 13b incremental A/D converter for high-linearity sensors read-out applications is described and characterized. The incremental solution is preferred to traditional SigmaDelta architectures to simplify the decimator filter topology, which is actually a single bit digital accumulator. This leads to lower area occupancy and power consumption. The input signal, which can be connected either in single-ended or differential mode, is sampled by a resettable SC integrator, followed by a discrete time comparator, which selects the feedback signal. The silicon prototype has been designed in 0.35mum technology with a power supply of 3.3V and consumes 950muW with throughput rate of 120Hz. The measurements results show an ENOB of 12.41 bits. The chip area is 0.22mm2.

Implementation of a novel read-out strategy based on a Wilkinson ADC for a 16/spl times/16 pixel X-ray detector array

In this paper we propose a Wilkinson type A/D converter as well as all the digital logic required for reading-out a 16/spl times/16 array of X-ray detectors. The proposed A/D converter architecture and read-out strategy allows us to handle an event rate as large as 10/sup 6/ event/s over the whole array and 10/sup 4/ event/s over the single row of the array with a resolution of 10 bits, consuming only 77 mW from a 3.3 V power supply. The A/D converter and the logic are embedded in an ASIC to be bump-bonded on top of the detector, which includes also the front-end electronics required for processing the sensor output signals. This work was done within the framework of an ESA research activity.

A CMOS 2D Micro-Fluxgate Earth Magnetic Field Sensor with Digital Output

A complete CMOS integrated microsystem for detecting the direction of the Earths magnetic field (whose full-scale value is on the order of 60muT), realized with the micromodule approach, including both sensor and electronic interface circuit, achieves 4deg accuracy on the measured angle and provides a digital output. The system response is linear in the range of plusmn60muT with a maximum non-linearity error of about 3% of full-scale.

A Clock-Less 10-bit Pipeline A/D Converter for Self-Triggered Sensors

In this paper a novel 10-bit pipeline A/D converter for low noise, self-triggered sensors is presented. The main innovative feature of the proposed A/D structure is the concept that a pipeline ADC may behave as a combinatorial logic and may operate without any timing signal (clock) in order to produce the conversion (assuming that a sampled signal is provided at the input). This concept is validated by the experimental results here reported. A prototype ADC has been fabricated in a standard 0.35mum CMOS technology, has an active area of 2.24mm2, provides a conversion in 2.5mus (400kS/s) and consumes 14mW from a 2.3V power supply

Multilayer PCB Planar Fluxgate Magnetic Sensor

This paper presents two high sensitivity vector-2D magnetic sensors for low magnetic field measurements. The sensors, based on the double axis Fluxgate principle, are realized in PCB technology. The amorphous magnetic material Vitrovac 6025X (25 mum thick) was used as a ferromagnetic core for the sensors. For the first sensor the magnetic material was glued on top of the PCB structure with a bi-adhesive tape, while for the second sensor the magnetic material was placed between two PCB layers in the fabrication process. Applying a sinusoidal excitation current of 600 mA peak at 10 kHz, the magnetic sensitivity of the first sensor is about 1.68 mV/muT, suitable for detecting the Earths magnetic field (plusmn60 muT), while the linearity error is 1.55% full scale. Using the second sensor, a maximum sensitivity of about 0.28 mV/muT and a linearity error of about 1.35% full scale in the range of plusmn60 muT are obtained with the same sinusoidal excitation current of 600 mA peak at 10 kHz. The 2D vector sensors presented are characterized by a very simple fabrication process thanks to the use of commercially available thin ferromagnetic material. This make these sensors useful for low cost applications where small dimension are not crucial

Behavioral model of magnetic sensors for SPICE simulations

This paper describes a general model for magnetic sensors to be used in portable systems. The model, written using the VERILOG-A language, enables the simulation of fully integrated solution. Physics and magnetic features of sensors are accounted for including second order effect like temperature, parasitic capacitance and contact resistance. The behavioral model obtains first magnetization and cycles completely customizable for the hysteresis calculation. The accuracy is very good without requiring heavy computation. The behavioral model describes magneto-resistances, magneto-inductances, flux-gate and Hall devices. The model is verified by computer simulations in the Cadence-Spice environment.

A CMOS 2D Micro-Fluxgate Earth Magnetic Field Detecting System with RS232 Digital Output

In this paper we present an acquisition system to measure the Earth magnetic field (whose full-scale value is of the order of 60 muT), consisting of a microcontrolled management subsystem, a CMOS integrated interface circuit and a 2D integrated micro-flux gate magnetic sensor. The couple of orthogonal axis of the sensor makes the system suitable for realizing an electronic compass device. The complete acquisition system achieves an accuracy resulting in a maximum error of 1.5deg in the measurement of the Earths magnetic field direction, providing a digital output through an RS232 serial interface. Furthermore a measurement setup was developed to evaluate the acquisition system performances. It consist of a precision mechanical structure, in tower form, of a PC software properly developed to post process the data from the acquisition system and of a Helmholtz Coils device to estimate the linearity of the system. This setup allows to perform a completely automated and numerically controlled characterization of the acquisition system.