TABLE OF CONTENTS Although many improvements have occurred over the past five years with the bandgap shunt reference, even more development has focused on the series type. This being the result of the individual design efforts of several leading U.S. analog semi- conductor manufacturers, including Analog Devices, LTC, Maxim, Microchip, National Semiconductor, Intersil, Texas Instruments, Semtech, Thaler, and Microsemi. Typically, series types provide superior performance to shunt types, in most of their characteristics, and in fact some of the newest series bandgap products now have features that challenge the high-performance topologies (i.e., the buried-zener, Analog Devices' XFET and Xicor's FGA ). These improvements with the series bandgap have brought about better initial accuracy ( %), lower temperature coefficients/drift, lower noise levels, lower dropout voltages, smaller package sizes, lower supply voltages, and lower power consumption. Improved products bring about higher accuracy and therefore better designs. The series bandgap reference is available in a three-pin (or more) format and in various package types that include DIL, throughhole, and surface mount. It also has more options available and is suitable for up to 14-bit applications. Unlike the shunt type, no input resistor is required, and low dropout devices are available for low-voltage/battery-powered applications.
The basic series voltage reference has an input terminal, an output terminal, and a ground return terminal, and is shown in Figure 15.8. Because series references do not need a bias resistor, they draw only a constant quiescent current, and the load current necessary, irrespective of...
