Continuous-time filter featuring Q and frequency on-chip automatic tuning

In this paper we report the on-chip automatic tuning of digitally programmable continuous-time G_m-C filters with a wide operation range employing a hybrid analog/fine-digital/coarse master-slave scheme. The tuning method, for both Q-factor and the characteristic frequency, is based on a digital phase comparator included in the phase-locked loop and achieves high-precision tunability. The digital frequency tuning is obtained with an error of plusmn4% and the maximum settling time when changing between two consecutive digital words is 0.3 mus. Once the digital word is fixed, the fine tuning finely adjusts the value of the characteristic frequency to the reference and corrects for possible temperature variations with an error of plusmn5% and a settling time of 0.2 mus.