A low-power 5-70-MHz seventh-order log-domain filter with programmable boost, group delay, and gain for hard disk drive applications

A seventh-order 0.05° equiripple linear-phase continuous-time filter employing log-domain-based instantaneous companding was designed and integrated in a mature bipolar process. The amount of boost (up to 13 dB) and group-delay adjustment (±30%) are digitally programmable. The dc gain is controllable up to 10 dB, and the -3-dB frequency (fc) is tunable from 5 to 70 MHz. The output swing for 1% total harmonic distortion is higher than 100 mV/sub pp/, with a 1.5-V supply. The filter consumes very low power (5-13 mW for fc=70 MHz) compared to conventional implementations (e.g., 120 mW for fc=100MHz ).