Programmable write head drive de-gaussing circuit

摘要

A write head drive circuit for a magnetic data storage device is configured to drive a write head with a write head degaussing current that is applied at the end of a write cycle. The write head degaussing current is an alternating current waveform with a programmable number of current pulses with decreasing amplitude and a frequency controlled by a CMOS ring oscillator. The CMOS ring oscillator includes switchable feedback paths to control its frequency. A programmable timer terminates the write head degaussing current after an interval of time dependent on signals that indicate the programmable number of current pulses and the frequency of the CMOS oscillator.