Multistage ADC based on integrating quantiser and gated ring oscillator

Dual slope ADCs have been shown to implement noise shaping when converted into integrating quantisers, turning amplitude information into time encoded pulses. A way to increase the resolution of an integrating quantiser is to use a gated ring oscillator (GRO) to estimate the pulse length. Such combination benefits from the noise shaping effect inherent to GROs. Hence, a noise shaping order increase can be achieved by a multistage configuration when an integrating quantiser is cascaded with a GRO. The architecture and behavioural simulation of such a MASH converter is discussed. Also, the on-line calibration of the noise cancellation filters is described.