12-bit accurate voltage-sensing ADC with curvature-corrected dynamic reference

Abstract

A sigma-delta analogue-to-digital converter (ADC) with a dynamic voltage reference is presented that achieves 12-bit absolute accuracy over the extended industrial temperature range (-40 to 105°C). Temperature-dependent gain errors due to the reference's curvature are digitally corrected by adjusting the gain of the ADC's decimation filter. The required correction factor is obtained by first using the reference to make a temperature measurement, and then translating the result into a correction factor by means of a lookup table and a linear interpolator. Thus, a dynamic voltage reference is realised with a measured temperature drift of less than 1.7 ppm/°C. The ADC was fabricated in 0.7 ?m CMOS technology and consumes 85 ?A from a 2.5-5.5 V supply.