A Precision Low-TC Wide-Range CMOS Current Reference

Abstract

<para xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> This paper describes a programmable temperature-compensated CMOS current reference. The proposed circuit achieves a first-order temperature compensation by canceling the negative temperature coefficient (TC) of an on-chip poly resistor with the positive TC of a MOS transistor operating in the ohmic region. Programmability of the current reference is enabled with the use of floating-gate transistors, thus allowing arbitrary current values to be set accurately. The temperature compensation is independent of the reference value; a low TC reference is possible for a wide range of currents. Prototypes from a 0.5 <formula formulatype="inline"><tex>$\mu{\hbox{m}}$</tex></formula> CMOS process exhibited a maximum temperature coefficient of 132 <formula formulatype="inline"><tex>${\hbox{ppm}}/^{\circ}{\hbox{C}}$</tex></formula> for a temperature range of 0<formula formulatype="inline"><tex>$\,^{\circ}{\hbox{C}}$</tex> </formula> to 80<formula formulatype="inline"><tex>$\,^{\circ}{\hbox{C}}$</tex> </formula>. Experimental results showed a current precision of 0.02% along with a line regulation of 1%/V for a supply voltage of 2.3 V to 3.3 V. These results were obtained for current references of 16 <formula formulatype="inline"> <tex>$\mu{\hbox{A}}$</tex></formula> to 53 <formula formulatype="inline"> <tex>$\mu{\hbox{A}}$</tex></formula> for five different prototypes. </para>