IMPLEMENTATION OF PRML IN A RIGID DISK DRIVE

The introduction of the IBM 0681 disk drive in January, 1990 marked an industry first for the application of a Partial-Response Maximum-Likelihood (PRML) data channel in a rigid disk drive. This paper describes the channel architecture, IC technology, and integration solutions used in implementing the 0681 data channel. A brief description of the 0681 disk drive is given along with a block representation of the data channel. Particular focus is placed on the major channel functions: equalization, data coding and detection, gain and timing recovery, and write circuitry. Both the analog and adaptive digital equalizer sections used in the channel are described. The 0681 channel uses an IBM mixed-mode IC technology to implement all channel functions. This IC process is illustrated, along with the PRML chip layout. Attention is also given to the hybrid nature of the PRML channel; many channel functions are implemented using a combination of both analog and digital circuits.