A Pll-based Floppy Disk Data Separator

Phase-lock techniques are widely used in a lot of aspects since 1930's. For example, phase-lock techniques are often used to establish coherent for tracking moving vehicles on space. In a television receiver, the horizontal and vertical scans are synchronized by a phase-locked loop (PLL). Using a PLL, the oscillator tracks out its own noise and its output is greatly cleaned up, and so on. The synchronization and separation of the data and clock from floppy disk driver are one of phase-lock techniques' use in computer field.This paper describes a PLL-based data separator which can work in floppy disk drivers at a read/write speed of 250Kbit/s,300Kbit/s,500Kbit/s and 1Mbit/s. The data separator has been integrated into a Super I/O chip employed practically on mother-board of personal computer. A 0.5μm CMOS process is used to fabricate the circuit.A digital-analog PLL is the main part of the data separator. The PLL has some improvements in accordance with the characteristic and the performance demand of floppy data separator. The major improvements include: employing a phase-frequency detector,reducing the start frequency difference and the start phase difference and employing a third-order filter. The phase-frequency detector can present a wide range (±2π) of linear comparison and a wide lock-in range. It can be used to improve PLL signal acquisition and cut down the pull-in time. When the start frequency difference suits inside the lock-in range,...