A high speed staggered servo pattern writing method for self clocking writers.
Original Publication Date: 2002-Aug-01
Included in the Prior Art Database: 2003-Jun-21
Disclosed is, a staggered servo pattern writing method with minimizing the recovery time from write to read operations for Hard Disk Drive servo writers with self pattern clocking technology. The self pattern clocking method to generate the servo write timing is applied for recent servo writers to reduce the timing jitter problem by replacing the external clock head. The staggered writing which writes several surfaces at once in a servo sector period is also very common to keep the writing time minimized. However, self clocking pattern occupies the recording area and needs to switch read and write operations to get the clock and embed the servo pattern and next clock pattern, so that the combination of the self clocking and staggered writing may run over the one servo sector timing period. Refer to figure 1. Here, one Servo ID (SID) is written every surface in a servo sector period. And clock timing pattern is written or read on a representative surface at the end of each sector period. The dominant reason of the overrunning is the GMR head bias voltage recovery time from write to read. Referring to the figure 2, GMR bias circuit, there is a capacitor which keeps the bias voltage to shorten the recovery time when the read operation starts at the same head before write. However, the write operation ends up at another head, the capacitor must be discharged not to damage the head by over bias across GMR, because of different resistance (generally lower) from that of the prior head. After, the bias voltage ramps up slowly and makes the recovery time longer. See the following table. Where, the conventional circuit does not have the S2, meaning always A side. S1 S1 S2 S2 bias loop cap bias vol at head Situation in wrt in rd in wrt in rd in wrt in rd in wrt in rd