Method of providing read bias during servo block write
AssigneeTexas Instruments Incorporated
InventorPaul M. Emerson
Life of this patent
Estimating the term…
Abstract
The manufacturer of hard disk drives (HDD) simultaneously activates all write heads to format the magnetoresistive disks during an operation known in the industry as “servo bank write”. To reduce bit error rates resulting from coupling between the write heads and the read heads during the servo bank write operation, the invention herein provides a relatively small amount of bias current to each read head when all the write heads are activated. The small bias current raises the dc bias level on the reader portion of the magnetoresistive head and effectively eliminates negative spikes resulting from the coupling.
Claims5
A method of preventing coupling in a magnetoresistive head of a disk drive during a servo block write operation, comprising the steps of:
- initiating the servo block write operation by selecting all write heads;
- selecting all read heads;
- and
- providing a bias current in all read heads during the servo block write operation using a circuit having a head select logic circuit, a plurality of MOSFET transistors, a plurality of sub-circuit portions, a feedback amplifier, and a bias current source, wherein the head select logic circuit includes a plurality of inputs and a plurality of outputs, the plurality of inputs coupled to each respective read head, the plurality of outputs coupled to each respective one of the plurality of MOSFET transistors, the plurality of sub-circuit portions coupled between the respective one of the plurality of MOSFET transistors and the bias current source, the plurality of sub-circuit portions coupled to each respective read head, the feedback amplifier coupled between the current source and the respective one of the plurality of MOSFET transistors.
A circuit to produce a bias current in each of a plurality of read heads of a hard disk drive assembly during a servo block write operation, having a power supply rail, comprising:
- a reference resistor coupled to the power supply rail to provide a reference voltage;
- a current mirror coupled to the reference resistor to produce a bias current;
- a load resistor coupled to the power supply rail;
- a plurality of sub-circuit portions, having a first and second bipolar transistor, each of the plurality of sub-circuit portions coupled to a corresponding one of the plurality of read heads, each bipolar transistor having a base, a collector and an emitter, the collector of each of the plurality of first bipolar transistors coupled to the load resistor, the base of each of the plurality of first bipolar transistors coupled to ground, the emitter of each of the plurality of first bipolar transistors coupled to the collector of each corresponding second bipolar transistor, the emitter of each of the plurality of second bipolar transistors coupled to a corresponding one of the plurality of read heads;
- a head select logic circuit, having a servo block write enable input, a plurality of inputs, and a corresponding plurality of outputs, each of the plurality of inputs coupled to a corresponding one of the plurality of read heads;
- a plurality of MOSFET transistors, each having a gate, a drain and a source, the gate of each of the plurality of MOSFET transistors coupled to the corresponding one of the plurality of outputs of the head select logic circuit, the source of each of the plurality of MOSFET transistors coupled to a corresponding base of the plurality of the second bipolar transistors;
- and
- a feedback amplifier having a first input, a second input and an output, the first input coupled to the load resistor, the second input coupled to the reference voltage, the output coupled to the drain of each of the plurality of MOSFET transistors;
- wherein the head select logic circuit couples to receive a servo block write enable signal at the servo block write enable input, wherein the head select logic circuit enables each of the plurality of MOSFET transistors corresponding to each of the plurality of read heads in response to an active servo block write enable signal to allow a small amount of the bias current to flow through each of the plurality of read heads.
Dependencies are inferred from the claim text.