100–1000 MHz cutoff frequency, 0–12 dB boost programmable Gm-C filter with digital calibration for HDD read channel

Abstract

A programmable Gm-C filter with digital calibration for hard disk drive read channels was developed. The filter has gm and boost tuning circuits and DC offset cancellation circuits. Moreover, it has two types of digital calibrations for achieving a robust filter response. One is an initial calibration to compensate for the filter response variations over process changes. The other is a periodic calibration to compensate for the variations over supply voltage and temperature changes. The periodic calibration operates in the duration between the servo and the data operation modes in the read channel. As a result, the filter response is robust over process, supply voltage, and temperature variations. The programmable range of the cutoff frequency and the boost are 100-1000 MHz and 0-12 dB, respectively.