A High Precise Reference for SAR ADC

A high precise bandgap is proposed and applied to a successive approximation register (SAR) analog-to-digital converter (ADC) used in the touch screen control system, which has a significant requirement of stability. Thus a lot of efforts were put into improving the precision and the reliability of the reference. As results, a high precise CMOS bandgap voltage reference circuit which is compatible with SMIC 0.35mum CMOS technology is proposed. The error sources in bandgap voltage reference are analyzed, and the precise mathematical expressions and the corresponding improvement methods are presented. The results show that the temperature coefficient is 16.9 ppm/degC over -40~85degC and the power supply rejection ratio is -71dB at 100 Hz.

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