RC-to-Digital Converter Using Single-Slope Integration with Bisection of the Reference Voltage

An RC -to-digital converter (RCDC) for the measurement of the RC time constant of the resistor and capacitor connected in series is presented in this paper. A simple RCDC design insensitive to the parasitic capacitances is based on the single-slope integration. The output voltage of the integrator is linearly changed from half the value of the reference voltage to its final value. The RC time constant is equal to the duration of the single-slope integration, and is independent of any other parameter. The proposed RCDC has been prototyped using discrete off-the-shelf components mounted on a printed circuit board, with a single supply voltage of 2.7 V. Measurements have been performed for 36 different combinations of the resistors and capacitors connected in series, where the measured time constant is in the range 45.77 μs < RC < 2.32 ms, for three different reference voltages. Achieved relative error is smaller than 1.96 % for the largest reference voltage used.