A constrained asymmetry LMS algorithm for PRML disk drive read channels

We present an implementation of a constrained least mean square (C-LMS) algorithm with application to magnetic disk drive read channels. The main advantage offered by the presented C-LMS algorithm is improved stability of the outer timing recovery loop while the spectral shaping of read-back data is performed in the inner adaptation loop. This eliminates any unstable behavior of the timing recovery loop during C-LMS algorithm adaptation. The proposed algorithm has been implemented and fabricated in a commercial read-channel using a 0.18 /spl mu/m L/sub eff/ CMOS technology. It operates at 550 MHz worst case.