A Low-Voltage Mobility-Based Frequency Reference for Crystal-Less ULP Radios

Abstract

<para xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> The design of a 100 kHz frequency reference based on the electron mobility in a MOS transistor is presented. The proposed low-voltage low-power circuit requires no off-chip components, making it suitable for application in wireless sensor networks (WSN). After a single-point calibration, the spread of its output frequency is less than 1.1% (3<formula formulatype="inline"><tex Notation="TeX">$\sigma $</tex></formula>) over the temperature range from <formula formulatype="inline"> <tex Notation="TeX">$-{\hbox{22}}\,^{\circ}{\hbox{C}}$</tex></formula> to 85<formula formulatype="inline"><tex Notation="TeX">$\,^{\circ}{\hbox{C}}$</tex> </formula>. Fabricated in a baseline 65<formula formulatype="inline"><tex Notation="TeX">$~$</tex></formula>nm CMOS technology, the frequency reference circuit occupies 0.11<formula formulatype="inline"><tex Notation="TeX">$\ \hbox{mm}^{2}$</tex></formula> and draws 34<formula formulatype="inline"> <tex Notation="TeX">$\ \mu\hbox{A}$</tex></formula> from a 1.2 V supply at room temperature. </para>