A high-performance calibration-free charge balancing analog-to-digital converter

This paper describes a robust charge-balancing analog-to-digital converter (ADC) for dc-voltage measuring applications. The converter, utilizing a continuous-time chopper-stabilized pulse-width modulator, has achieved an absolute accuracy of 20 bits at room temperature, without any trimming or calibration. Within a temperature range of -50/spl deg/C to 125/spl deg/C, the accuracy changes with a temperature coefficient of 0.05 ppm//spl deg/C. The modulator is implemented by employing commercial discrete components.