A Modified Current Mode Bandgap Reference with 15.1ppm/<sup>0</sup>C Temp Coefficient in 28nm CMOS
R. Nagulapalli, Immanuel Raja
Abstract
Conventional Sub-1V bandgap reference circuit does not provide PTAT current and it has several stable operating points. All of the existing problems are explained intuitively in this paper. A modified sub-1V reference circuit was proposed, by injecting the PTAT current into a BJT and potential divider. Also, residual systematic offset is one of the major temperature coefficient contributor. In this work a novel currentmirror based self-biased opamp has been proposed which minimized the systematic offset by more 36%. A prototype has been developed in 28nm and post-layout simulations are presented. The minimum VDD is 1V while providing 450mV reference voltage with a line regulation of 1.2%. A temperature coefficient of 15.1ppm/ <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sup> C has been achieved over the industrial range of -40 to 125 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sup> C. The circuit draws 25uA at high temperature and occupies 1192um <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> silicon area.