Self-tuning method and apparatus for continuous-time filters

摘要

A self-tuning technique for integrated continuous-time filters. The present invention provides a method and apparatus to compensate for post- fabrication or in-operation discrepancies between desired and measured filter characteristics due to variability of the IC fabrication process or due to drift caused by changing conditions such as voltage, temperature. The present invention requires minimal overhead in power and area requirements. Furthermore, the filter being tuned is used to process signals, unlike in the prior art where a similar but separate filter or oscillator is used to tune the bias values for both circuits. Better tuning accuracy is thus obtained in the present invention. The circuit is designed to initiate a self-tuning cycle at power-up or during operation after power-up. Tuning is achieved by injecting a reference signal, and monitoring the phase of the filter output with respect to the phase of the reference signal. The self-tuning circuit then provides a signal to a trim DAC, which applies the appropriate correction signal.