By exploiting floating-gate-analog (FGA) technology, two 5.0-V voltage references can achieve high levels of accuracy despite their very low current consumption. Members of Xicor's X60008 family, these SO-8 packaged chips guarantee an absolute initial accuracy as precise as ±0.5 mV. At the same time, they specify a maximum current consumption of 800 nA with typical performance given as 500 nA.
The stability of the references over time and temperature is also noteworthy. Long-term stability is rated as 10 ppm/1000 hrs, while straight-line temperature coefficients are specified to 5 ppm/°C (see the figure). The two versions of the reference include a C grade part (model X60008CIS8-50) with the aforementioned ±0.5-mV initial accuracy and 5 ppm/°C temperature stability. There's also a D grade part (X60008-DIS8-50) with these specifications relaxed to ±1.0 mV and 10 ppm/°C. Pricing starts at $4.55 for the C grade and $3.15 for the D grade in quantities of 1000.
"Current voltage references that achieve initial accuracies tighter than ±1 mV with temperature stability less than 5 ppm/°C are expensive as well as limited in availability due to the limitations of current technologies," says Davin Lee, vice president of marketing for Xicor.
Unlike the existing buried-zener and bandgap technologies, Xicor's FGA technology works by storing the reference voltage as a precisely controlled charge on a floating gate device. (For a description of the underlying technology, go to www.xicor.com/FGA.)
A tradeoff in getting such high accuracy is noise performance. The X60008 5-V references specify 30 µV p-p typical over a 0.1- to 10-Hz bandwidth. Nevertheless, the company plans to improve the noise specifications of its voltage references in the future. Over the course of the year, Xicor also will introduce other X60008 family members with voltage options down to 0.9000 V, initial accuracy as tight as ±0.25 mV, and temperature coefficients as precise as 1 ppm/°C. Voltage references with faster transient response and smaller package options are also in the works.