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

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.