A 10-bit linearity current-controlled ring oscillator with rolling regulation for smart sensing

This paper presents a highly linear current-controlled ring-oscillator (CCRO) circuit for current-to-frequency ADC in smart sensing. The proposed CCRO topology employs a distributed regulation of the oscillator rail voltage for lowering its sensitivity with respect to the controlling input current. The use of a current conveyor for this purpose ensures the stability of the current-steering control loop together with low-area and low-power overheads. A practical circuit design example is supplied in 0.18-μm 1P6M CMOS technology consisting on a 10-bit 100-kS/s ADC without the need of any digital calibration nor postcompensation technique.