Configurable write current overshoot system for hdd write driver

Abstract

A hard disk drive write drive method and integrated circuit that provide a configurable overshoot current based on the length of the pattern in the write current signal that is being written to the hard disk by the write driver. The hard disk write driver adds a first overshoot current to all patterns in the write current signal and adds an additional second overshoot current to patterns in the write current signal shorter than a first duration. The hard disk drive write driver utilizes an H-bridge circuit configured to add the first overshoot current and the additional second overshoot current to the write current signal. The H-bridge circuit is comprised of four switching elements that are configured to generate a first overshoot current for all pattern transitions of the write current signal and generate a second overshoot current for pattern transitions shorter than the first duration.

What is claimed is: 
     
         1 . A process of forming a write current signal used in a hard disk drive comprising:
 (a) receiving a write data input signal having data pulses, each data pulse having a start transition, an end transition, and a time T in length between transitions, and the time T between transitions of different pulses are integral numbers of time T in length;   (b) generating a write current signal of write pulses having start transitions in accordance with the data pulses of the write data input signal;   (c) determining the lengths T of the data pulses;   (d) for data pulses having a length T greater than 1T, producing a first overshoot current at the start transition of a write pulse for a first time duration and a first current value; and   (e) for data pulses having a length of 1T, producing a second overshoot current at the start transition of a write pulse for a second time duration and a second current value.   
     
     
         2 . The process of  claim 1  in which the first time duration and the second time duration are the same. 
     
     
         3 . The process of  claim 1  in which the first current value is Ios and the second current value is Ios+IosADD. 
     
     
         4 . The process of  claim 1  in which sequential write pulses are of opposite polarity. 
     
     
         5 . The process of  claim 1  in which the first and second durations are less than the length of a write pulse. 
     
     
         6 . A process of forming write signal current pulses used in a hard disk drive from write data signal pulses having integer lengths T comprising:
 (a) for write data signal pulses having a length greater than 1T, producing a first overshoot current at a leading edge of a write signal current pulse for a first time duration and a first current value; and   (b) for write data signal pulses having a length of 1T, producing a second overshoot current at the beginning of a write signal current pulse for a second time duration and a second current value.   
     
     
         7 . The process of  claim 6  in which the first time duration and the second time duration are the same. 
     
     
         8 . The process of  claim 6  in which the first current value is Ios and the second current value is Ios+IosADD. 
     
     
         9 . The process of  claim 6  in which sequential write data signal pulses are of opposite polarity. 
     
     
         10 . The process of  claim 6  in which the first and second durations are less than the length of a write signal current pulse. 
     
     
         11 . A process of forming write signal current pulses used in a hard disk drive from write data signal pulses having integer lengths T comprising:
 (a) determining the lengths T of individual write data signal pulses;   (b) generating write signal current pulses having leading edges in response to the write data signal pulses;   (c) adjusting overshoot current pulses applied to the leading edges of the individual write signal current pulses depending upon the length T of each write data signal pulse.   
     
     
         12 . The process of  claim 11  in which the adjusting includes adjusting durations of the overshoot current pulses. 
     
     
         13 . The process of  claim 11  in which the adjusting includes adjusting current values of the overshoot current pulses. 
     
     
         14 . The process of  claim 11  in which the adjusting includes:
 (a) for write data signal pulses having a length T greater than 1T, producing a first overshoot current at the leading edge of a write signal current pulse for a first time duration and a first current value; and 
 (b) for write data signal pulses having a length of 1T, producing a second overshoot current at the beginning of a write signal current pulse for a second time duration and a second current value 
 
     
     
         15 . The process of  claim 14  in which the first time duration and the second time duration are the same. 
     
     
         16 . The process of  claim 14  in which the first current value is Ios and the second current value is Ios+IosADD. 
     
     
         17 . The process of  claim 11  in which sequential write data signal pulses are of opposite polarity. 
     
     
         18 . The process of  claim 11  in which the first and second durations are less than the length of a write signal current pulse.