A High-Resolution Oscillator Based Resistance-to-Digital Converter with Non-Linearity Canceling Feedback by ΔΣ Modulated Variable Resistor

A Time-Domain Resistance-to-Digital Converter (RDC) with a referential 1-bit ΔΣ Modulated variable resistor is proposed. The proposed RDC converts an input resistance to a frequency and compares a referential variable resistor to decrease a sensor read-out error caused by a non-linearity of an oscillation frequency. A 1-bit ΔΣ modulated variable resistor is demodulated by an oscillator and a counter. Hence a low-pass filter circuit is not required. In addition, non-linearity canceling feedback is proposed to decrease comparison time. This prototype RDC achieves 10.1bits conductance resolution at 1kSps in 10μS to 110μS full-scale range.