A 550 MSample/s 8-tap FIR digital filter for magnetic recording read channels

With the advent of partial response maximum likelihood (PRML) equalization of magnetic recording channels, spectral shaping of read back signal is typically performed by combination of a continuous time and a digital FIR filter. Digital FIR filters are scalable with technology and can be adapted to provide a desired channel response typically using the least mean square (LMS) algorithm in commercial read channels. For these reasons, use of continuous time filters for this application is gradually diminishing. Efficient timing recovery in a read channel is critical for fast phase and frequency acquisition in addition to acceptable bit error rate (BER) performance. Therefore, it is also critical that these filters are implemented with as little latency as possible since their output is used to extract timing information.