C.A. dos Reis Filho

An integrated CMOS instrumentation amplifier with improved CMRR

An instrumentation amplifier is described, which is based on the classical current-balancing technique that ensures this type of circuit achieves high immunity to common-mode signals. In the particular case of the circuit herein described, a CMRR of 110 dB was attained, thanks specially to improving the current mirror that balances the current between the input and the output stages of the amplifier. Prototypes of the circuit were fabricated in 0.6 /spl mu/m CMOS using MPW (multi-project wafer) services and were fully characterized.An instrumentation amplifier is described. which is based on the classical current-balancing technique that ensures this type of circuit to achieve high immunity to common-mode signals. In the particular case of the circuit herein described. a CMRR of I lOdB was attained, thanks specially to improving the current mirror that balances the current between the input and the output stages of the amplifier. Prototypes of the circuit were fabricated in O.6µ CMOS using MPW (Multi-Project Wafer) services and were fully characterized.

Magnetically-coupled current sensors using CMOS split-drain transistors

Integrated current sensing circuits intended for Smart-Power and embedded applications featuring galvanic isolation are implemented. They are based on magnetic detection using the CMOS compatible split-drain transistor (MAGFET) that provides a very linear output current versus magnetic field. Two approaches are used to generate the magnetic field. The Coil approach and the Strip approach. In the first one the current to be sensed flows through an integrated coil placed atop the split-drain transistor and produces a relatively strong magnetic coupling enough to cause a detectable current. The second approach features an array of 126-paralleled split-drain transistors along a metal strip intended to carry higher current levels. Both techniques were realized as integrated current sensors built in 0.35 mum CMOS technology. The calculated and measured sensitivities were around 1 muA/A and 0.75muA/radicA for the Coil and Strip approaches respectively. For a typical single split-drain bias current of 50 muA, the minimum detectable current within 1Hz are 2.8 muA/radicHz and 42 muA/radicHz for the Coil and Strip approaches respectively. The Strip can carry currents up to 500 mA, whereas the flowing current in the Coil is limited to 20 mA. Thus, the choice is based on the resolution and sensing current level of the application.

Capacitive-SAR ADC input offset reduction by stray capacitance compensation

A 10-bit, 80-kS/s charge-redistribution successive approximation analog-to-digital converter is presented, which incorporates a novel stray capacitance compensation technique that is appropriate for low-power design in order to accomplish input voltage offset reduction. Three different versions of the ADC were fabricated in 0.35 mum, 4M2P standard CMOS process. The compensation mechanism implemented in one of the ADC versions proved its effectiveness by showing an input voltage offset that is circa 60 times smaller than what was measured in the other two uncompensated versions. Also from fabricated samples of the compensated ADC, measured values for INL and DNL are 0.47 LSB and 0.58 LSB, respectively. Operating at 3.3V at the nominal speed, the offset-compensated ADC consumes 122 muW.

Analog CMOS tesla-volt multiplier circuit

This paper describes a simple CMOS analog circuit that performs the multiplication of an external bipolar voltage, e, by an applied magnetic field B. The circuit uses an arrangement of split-drain MOS transistors operating in the saturation region to produce an output difference current that is proportional to (B/spl times/e). If the external voltage e is a fraction of the mains voltage and B is produced by the corresponding current, the output signal is a measure of the instantaneous power. Measurements of a test circuit, which was built with discrete transistors fabricated in CMOS 0.8 /spl mu/m technology, have shown that a monolithic mixed-signal solution for single phase power consumption metering based on this concept is technically feasible.

Monolithic data circuit-terminating unit (DCU) for a one-wire vehicle network

This paper describes a chip designed to perform the function of a Data Circuit-Terminating Unit (DCU), which provides an interface of smart sensors, actuators and subnets into a one-wire ring-topology vehicle network called BAM2. The monolithic DCU interprets the messages of a proprietary two-frames polling-access protocol operating in 38.4Kbps. Instead of having a physical address assigned to each DCU, as usual in the realm of vehicle networks, every DCU in the BAM2 network is assigned a logical address by the Master unit, thus allowing easy exchangability and maintenance of the DCUs as well as the reduction of cost of both production and assembling of the network. Prototypes of the chip were fabricated in 0.8µ m5V CMOS technology in an area of 8.7mm2. Experimental results are presented.

Fully integrated programmable Howland current source for sensors excitation

In this paper a fully integrated implementation of the classical Howland current source is presented as a compact solution for exciting resistive and piezoresistive sensors. This circuit, which is part of a programmable signal conditioning microsystem, described elsewhere, is treated as a module that is capable of providing a voltage-adjustable current whose full-scale is 10 mA. Experimental results from samples manufactured in 0.8 /spl mu/m CMOS have shown that the circuit features a full-scale nonlinearity of 0.042% powered by a supply voltage of 5 V. The measured frequency response using a 50 /spl Omega/ resistive load rolls off at 228 kHz, which is in excess of the predicted applications.

MAGFET with embedded Gilbert gain cell

A modified Gilbert gain cell implemented with lateral-PNP transistors has been successfully used to amplify the output current signal from an N-channel split-drain MOS transistor, or MAGFET. Compared with other previously reported signal conditioning circuits for MAGFETs, the herein presented approach adds the advantage of featuring programmability for the current gain, thus providing means of controlling the sensitivity of the magnetic detecting device. Measurements of prototypes of the circuit, fabricated in 0.35mum CMOS, have proved the concept.

Bluetooth sensor network for remote diagnostics in vehicles

This paper describes the implementation of a system by means of which the data from sensors is installed in vehicles can be transmitted wirelessly through a Bluetooth network. The targeted application or the developed system is remote diagnostics. Results from several experiments, measuring the transmission of data for different arrangements of Bluetooth nodes inside vehicles, are presented and discussed.

Analog triangular-to-sine converter using lateral-pnp transistors in analogue pCMOS process

This paper focuses on the development of a monolithic analog triangular-to-sine converter that is based on the same technique as that devised by Barrie Gilbert [1977], which exploits the fact that a hyperbolic-tangent series converges to the sine. The novelty in the described circuit is the implementation of the sine shaper in CMOS process using lateral-pnp bipolar transistors. Due to the excellent performance of the used lateral-pnp transistors at low current levels, the elected circuit implementation is mostly appropriate for low-power operation. Experimental results from prototypes of the circuit fabricated in 0.6 /spl mu/m CMOS have shown that the deviation from ideal sine over the -/spl pi//2 to /spl pi//2 range is less than 0.5%.

Elements for a monolithically integrated rotation imbalance detector

The main focus of this paper is a description of a set of analog circuits, which are the essential parts of an integrated microsystem to detect imbalance in rotating machines. The system comprises an instrumentation transconductance amplifier at the front end, whose role is to provide an appropriate conditioning for the signal produced by an accelerometer that senses the vibration caused by the rotation motion of the machine and a pair of triangular- to-sine converters operating with a constant phase difference of 90 degrees. By multiplying the vibration transducer signal by the generated sine and cosine, the system determines the Cartesian coordinates of the imbalance vector. Auxiliary circuits like a bandgap reference and a pair of low-pass filters are also part of the system. All these elements were implemented in 0.6 /spl mu/m CMOS using multi-project wafer services and fully characterized. Experimental results are presented and discussed.