Rogelio Palomera

Introduction to embedded systems : using microcontrollers and the MSP430

Introduction.- Number Systems and Data Formats.- Microcomputer Organization.- Assembly Language Programming.- Embedded Programming Using C.- Fundamentals of Interfacing.- Embedded Peripherals.- External World Interfaces.- Principles of Serial Communication.- The Analog Signal Chain.-

Undergraduate research and co-op education: a winning combination

The Electrical and Computer Engineering (ECE) Department of the University of Puerto Rico at Mayaguez (UPRM) in collaboration with renowned engineering companies has developed and implemented an educational model joining traditional co-op education and undergraduate research experience. The model has evolved into a well-rounded learning program with important benefits for all parties involved: students, academia, and employers. This paper describes the program, presents statistics quantifying its impact, and identifies key elements for the success of the approach.

Automated wafer-level measurement of LDMOS reverse recovery parameters

Accurate measurement of reverse recovery parameters (RRPs) in high-speed, high-power switches and rectifiers is a fundamental task in their test and characterization process. Performing such tests at a wafer-level in laterally diffused MOSFETs (LDMOS) presents several challenges with respect to their test in packaged devices. The handling of prober parasitic impedances, current injection constraints, and automated signal synchronization top the list of issues that need to be addressed. Moreover, making the tests amenable for automated execution just adds more constraints to the problem. This paper proposes a solution for automatic characterization of wafer-level LDMOS RRPs that include reverse recovery time (trr), reverse recovery current (Irr), and storage charge (Qrr). Its implementation has enabled accurate automated parametric wafer-level LDMOS tests at currents as high as 15A and ∂I/∂ts of up to 173A/μs.

Design of a CMOS 1.8V low voltage differential signaling receiver

The design of a 1.8V LVDS receiver operating at a maximum speed of 700Mbits/sec is presented. The receiver is designed to accept LVDS signals from 3.3V, 2.5V, or 1.8V systems and converts it to a 1.8V digital data. The design was completed on a 0.24/spl mu/m CMOS process and complying with the industry standard of /spl plusmn/10% power supply variations over a temperature range from -40/spl deg/C to +85/spl deg/C. At the nominal supply voltage of 1.8V and operating at maximum speed the receiver consumes less than 6.5mW.

Design review and innovations in low-voltage differential signaling drivers

Technological advances in high-speed, wired communications increasingly require reliable data transmission circuits. Among the transmission techniques developed for this purpose, one of the most successful has been based on low voltage differential signals (LVDS). This paper discusses different techniques employed in the design of LVDS circuits, introducing design innovations to provide line drivers with adjustable common mode voltage.

A virtual instrument design for low-cost charge-pumping characterization of integrated MOSFETs

Charge pumping techniques are used to characterize and quantify the interface state densities in Metal-Oxide-Semiconductor Field-Effect Transistors (MOSFET). When carried in a semiconductor production line, this technique needs to be time efficient, calling for automated testing environments. Moreover, the cost of the characterization equipment used in the test is always a factor of relevance for budget conscious operation. In this paper we present the design of an automated Virtual Instrumentation Environment (VIE) for performing charge pumping characterization using low cost, off-the-shelf instrumentation. A discussion is presented of tradeoffs and design considerations for obtaining a functional design without compromising test flexibility and accuracy.

Assembly Language Programming

Programming provides us with the flexibility to use the same hardware core for different applications. A device whose performance can be modified through some sort of instructions is called a programmable or configurable device. Most I/O ports and peripherals are examples of these blocks; their configuration should be part of our program design.

Comparative analysis and parameter extraction automation of annular MOSFETs

Gate-enclosed MOSFETs are commonly used for extreme environments with constant radiation exposure due to its radiation tolerance. Because of its annular geometry, the standard BSIM3 models do not accurately represent what happens physically on the device. An accurate model extraction can take months to complete, thus the need for a fast extraction method. Of the several model extraction methods, the authors chose to extract the parameters through a method called conformal mapping. The mapping is performed using a Schwarz-Christoffel transformation. This allows the mapping of any arbitrary geometry into a well-known rectangular geometry. Additional parameters that change because of the geometry are recalculated for an accurate representation of short-channel effects and parasitic effects. Test chips with annular and rectangular devices were fabricated by MOSIS on AMI 0.6μm process technology. The SPICE model automation is performed with a Keithley Sourcemeter 2612 using LABVIEW. A call operation is performed to MATLAB to calculate aspect ratio using the mapping transformation toolbox. The final SPICE model should contain at least 22 parameters. This extraction can be performed in minutes on a laptop computer, allowing standard simulation without the need to create a separate device.

Number Systems and Data Formats

To understand how microcontrollers and microprocessors process data and work, we must adopt symbols and rules with proper models to mimic physical operations at a human friendly level. Digital systems operate with only two voltage levels to process information. As part of the modeling process, two symbols are associated to these levels, ‘0’ and ‘1’. Any consecutive concatenation of these two symbols, in any order, is referred to as a word. Words are used as mathematical entities and abstract symbols to represent all sort of data. We refer to words as integers, thereby simplifying not only the description and manipulation of the strings, but also programming notation and hardware processes.

Principles of Serial Communication

Serial channels are, without doubt, the main form of communications used in digital systems nowadays. Diverse forms of serial communication formats and protocols can be found in applications ranging from short inter- and intra-chip interconnections, to the long range communication with distant spaceships traveling to other planets.