Piero Malcovati

Curvature-compensated BiCMOS bandgap with 1-V supply voltage

In this paper we present a bandgap circuit capable of generating a reference voltage of 0.54 V. The circuit, implemented in a submicron BiCMOS technology, operates with a supply voltage of 1 V. In the bandgap circuit proposed we use a non-conventional operational amplifier which achieves virtually zero systematic offset, operating directly from the 1 V power supply. The bandgap architecture used allows a straightforward implementation of the curvature compensation method. The proposed circuit achieves 5 ppm / K of accuracy without requiring additional operational amplifiers or complex circuits.

Modeling sigma-delta modulator non-idealities in SIMULINK(R)

This paper presents a complete set of SIMULINK(R) models, which allow exhaustive behavioral simulations of any sigma-delta modulator to be performed. The proposed set of models takes into account most of the sigma-delta modulator non-idealities, such as sampling jitter, kT/C noise and operational amplifier parameters (noise, finite gain, finite bandwidth, slew-rate and saturation voltages). For each model we present a description of the considered effect as well as all of the implementative details. Simulation results on a second-order switched-capacitor sigma-delta modulator demonstrate the validity of the models proposed.

A 9.4-ENOB 1V 3.8μW 100kS/s SAR ADC with Time-Domain Comparator

The ADC-SAR is fabricated in a 0.18mum 2P5M CMOS process. This SAR-ADC converter achieves 56fJ/conversion-step FOM with 58dB SNDR. It uses a comparator, named time-domain comparator, that instead of operating in the voltage domain, transforms the input and the reference voltages into pulses and compares their duration.

Two-dimensional magnetic microsensor with on-chip signal processing for contactless angle measurement

The reported CMOS microsystem is the key element for accurate angle measurements. In combination with a permanent magnet, it is used for various wear free angular positioning control systems for automotive and industrial applications covering the full 360/spl deg/ range. The integrated system includes a two-dimensional (2-D) magnetic microsensor (30/spl times/30 /spl mu/m/sup 2/ active area), offset compensation, and signal conditioning circuitry. A novel approach for the angle calculation is presented using an on-board incremental ADC. A bitstream representing the angular position of the applied permanent magnet is provided at the system output. The system achieves a 1/spl deg/ angular resolution with 9 mW power consumption and a permanent magnet of 100 mT. The chip is fabricated in a generic 2-/spl mu/m, double-poly, double-metal CMOS process and covers an area of 2.6/spl times/4.1 mm/sup 2/.

A 141-dB Dynamic Range CMOS Gas-Sensor Interface Circuit Without Calibration With 16-Bit Digital Output Word

In this paper, we present the design and the characterization of a wide-dynamic-range interface circuit for resistive gas-sensors able to operate without calibration. The circuit is based on resistance-to-frequency conversion, which guarantees low complexity. The state-of-the-art of this measurement method has been improved first by separating the resistance value controlled oscillator circuit (RCO) from the sensing device, thus leading to higher linearity performance, and then by exploiting a novel digital frequency measurement system. Measurement results on a silicon prototype, designed in a 0.35-mum CMOS technology, show that the circuit achieves, without calibration, a precision in resistance measurement of 0.4% over a range of 4 decades and better than 0.8% over 5 decades (dynamic range, DR = 141 dB). Furthermore, after calibration, it reaches a precision of 0.4% for resistance values ranging between 1 kOmega and 1 GOmega, thus leading to a DR of 168 dB. The prototype chip consumes less than 15 mW from a 3.3-V supply.

A 200mA 93% Peak Efficiency Single-Inductor Dual-Output DC-DC Buck Converter

A single-inductor dual-output DC-DC buck converter is presented. The inductor, which is external, provides two independent output voltages ranging from 1.2V to the power supply with a maximum total output current of 200mA. The supply can range from 2.6 to 5V. The converter is fabricated in a 0.35mum p-substrate CMOS technology. Measurement results demonstrate that a peak power efficiency as high as 93.3% can be achieved and the efficiency is always >62.5%.

A 4-Output Single-Inductor DC-DC Buck Converter with Self-Boosted Switch Drivers and 1.2A Total Output Current

Minimizing power consumption in multi-processor systems requires the use of multiple supplies with a wide range of regulated voltages and currents. Since one inductor per DC-DC converter is expensive, there is an increasing interest in single-inductor-multiple-output (SIMO) DC-DC converters. Recent research results report a SIMO boost converter and various boost or buck converters with two outputs. This 0.5mum CMOS system is a four- output, single-inductor buck converter with independent regulation of each output.

A 160 dB Equivalent Dynamic Range Auto-Scaling Interface for Resistive Gas Sensors Arrays

In this paper an integrated wide-dynamic-range interface circuit for resistive gas-sensors arrays is presented. The proposed device consists of a multiscale transresistance continuous time amplifier followed by a 13-bit incremental A/D converter. The circuit selects automatically the scale to use for each measurement and includes two digital-to-analog converters for the calibration of offset and gain of each scale. The proposed interface circuit achieves a measurement accuracy almost always better than 0.1 % over a sensor resistance range of more than 5 decades [100 Omega-20 MOmega], leading to an equivalent dynamic range of about 160 dB. The chip has been realized with a 0.35 mum CMOS technology and occupies an area of 3.1 mm2 consuming 6 mW from a 3.3 V power supply.

Smart sensor interface with A/D conversion and programmable calibration

In this paper we present a new architecture for a smart sensor interface. It is based on an oversampled A/D converter associated with a small ROM containing calibration coefficients. The nonlinear function desired is obtained by piecewise linear interpolation between the values stored in the ROM, without any additional circuits. This solution has the advantage of high programming flexibility, long-term stability, and low area consumption. Moreover, it is suitable for co-integration with sensors because of its minimum analog content. A prototype was integrated in a CMOS 1.2-/spl mu/m technology. Simulation and experimental results are reported together with a detailed theoretical analysis and some design guidelines. >

Design considerations on low-voltage low-power data converters

In this paper, we discuss theoretical and practical issues concerning low-voltage and low-power data converters. By looking at a series of constraints affecting the design of basic elements and building blocks, the paper analyzes different architectures for Nyquist rate data converters and discusses important aspects of low-voltage and low-power operation. Following this, the minimization of power consumption in the very popular sigma-delta technique is considered. A number of hints and indications are provided throughout the paper.