A Digital Controller Assisted Flexible Auto-tuning Method for Continuous-time Filters

A novel auto-tuning method for the integrated continuous-time filter is proposed in this paper. On the one hand, an off-chip digital controller is adopted here to decrease the on-chip hardware as well as to increase the efficiency and the flexibility of the auto-tuning strategy. As a result, both the calibration and the programmability of the cut-off frequency can be realized by software, meanwhile some non-idealities of the circuit can also be compensated by software. On the other hand, the on-chip auto-tuning circuit is designed based on the master-slave architecture, where a novel and simple master circuit is adopted with digital input and output interfaces, thus providing convenient connections for the controller without the ADC or DAC devices. With the PCB technology, a 6th-order active-RC filter with the proposed auto-tuning method is also implemented to verify the validity and the flexibility of this method.