Circuits and methods for optimizing write current waveform for main pole relaxation in perpendicular magnetic recording

A method for determining a main pole relaxation zone in a write current for a PMR write head within the head arm assembly, comprising the steps of:

• encoding data into an NRZI modulated conversion code word that is to be written to the perpendicular magnetic recording head to an NRZI encoding format;
• determining a data frequency and bit length of the encoded data;
• determining an overshoot duration of a current overshoot zone;
• generating a constant write current zone;
• setting the amplitude of the overshoot current zone as the difference between a peak current of the overshoot current zone and a constant write current of the constant write current zone;
• determining a duration of the main pole relaxation zone;
• comparing the overshoot duration of the NRZI modulated conversion code word with the number of clock transitions of NRZI modulated conversion code word;
• when the NRZI modulated conversion code word time interval is less than or equal to the number of clock transitions, setting the pulse amplitude and duration of the NRZI modulated conversion code word to the overshoot amplitude and the overshoot duration;
• and
• writing the head current to the PMR write head.

A magnetic hard disk drive comprising:

• a controller comprising:
• an ECC generator for receiving input data and generating an ECC code word appended to the input data;
• an NRZI write encoder for converting the input data with the appended ECC code word into an NRZI modulated conversion code word;
• and
• a preamplifier mounted on the head arm assembly and connected to a controller circuit for receiving an NRZI modulated conversion code adapted from the input data, the preamplifier comprising:
• a main pole relaxation control circuit configured for generating a main pole relaxation zone current that is concatenated with an overshoot current zone of a magnetic head write current applied to a PMR write head within the head arm assembly, wherein the main pole relaxation control circuit comprises:
• a main pole relaxation zone data synchronization circuit that is in communication with a read data preamplifier to receive a pseudorandom read data signal that is dependent on the bit length of the encoded data, wherein the pseudorandom read data signal is applied to a main pole relaxation zone data synchronization circuit to generate a main pole relaxation current to be concatenated with the overshoot current;
• and
• a comparator/selector configured for determining waveform of the main pole relaxation zone current, wherein the output of the main pole relaxation control circuit is applied to a write current driver and an overshoot driver to concatenate the main pole relaxation zone current with the overshoot current and the write current to form a write data current signal that is applied to the PMR write head for writing the encoded data to the HDD media.