Hybrid termination of transmission line for driving hard disk drive head

A hard disk drive comprising:

• a rotatable magnetic medium;
• a read/write head to read and write magnetic information to a surface of the rotatable magnetic medium, wherein the read/write head is supported for scanning movement across the surface of the magnetic recording medium;
• a controller to generate an information signal based on information to be written to the magnetic recording medium, the controller further to control the scanning movement of the read/write head;
• drive circuitry to differentially drive the read/write head through a differential pair of transmission lines, the differential pair of transmission lines being connected to the drive circuitry through corresponding first and second connections in accordance with the information signal;
• wherein the drive circuitry comprises positive-going drive circuitry, negative-going drive circuitry and termination circuitry, which comprises:
• a first steady state supply resistor connected in series with a first steady state supply switch between a positive power source and the first connection;
• a first steady state termination resistor connected in parallel with a first steady state termination switch across the first connection;
• a first boost supply switch connected in series between the positive power source and the first connection;
• a second steady state supply resistor connected in series with a second steady state supply switch between a negative power source and the second connection;
• a second steady state termination resistor connected in parallel with a second steady state termination switch across the second connection;
• a second boost supply switch connected in series between the negative power source and the second connection;
• a third steady state supply resistor connected in series with a third steady state supply switch between the negative power source and the first connection;
• a third boost supply switch connected in series between the negative power source and the first connection;
• and
• a fourth steady state supply resistor connected in series with a fourth steady state supply switch between the positive power source and the second connection;
• a fourth boost supply switch connected in series between the positive power source and the second connection;
• wherein the controller includes a switch controller configured to operate in a positive-going current supply mode and a negative-going current supply mode;
• wherein in the positive-going current supply mode, the third and fourth boost supply switches and the third and fourth steady state supply switches are all controlled to be open, the first and second boost supply switches are controlled to be closed during a boosted period of driving the load, and thereafter the first and second boost supply switches are controlled to be opened during a steady state period of driving the load, wherein during the steady state period, the first and second steady state supply switches and the first and second steady state termination switches are all controlled to be closed;
• and
• wherein in the negative-going current supply mode, the first and second boost supply switches and the first and second steady state supply switches are all controlled to be open, the third and fourth boost supply switches are controlled to be closed during a boosted period of driving the load, and thereafter the third and fourth boost supply switches are controlled to be opened during a steady state period of driving the load, wherein during the steady state period, the third and fourth steady state supply switches and the first and second steady state termination switches are all controlled to be closed.

A method for operating drive circuitry which drives a load through a transmission line, the drive circuitry comprising a connection to the transmission line and a steady state supply resistor connected in series with a steady state supply switch between a power source and the connection, the method comprising:

• closing a boost supply switch during a boost period of driving the load;
• and
• thereafter opening the boost supply switch during a steady state period of driving the load;
• wherein during the steady state period, the steady state supply switch and a steady state termination switch are both closed.