Bimodal biasing of magneto resistive heads

#The invention is related generally to storage devices and, in particular, to biasing of magneto resistive heads for memory devices.

#Magneto resistive heads (or MR heads) are used in data storage devices, such as disk drives, tape drives, removable and flexible media drives, etc., where data is stored on the data storage media (or disks) in the form of small, permanently magnetized regions. The magnetized regions produce magnetic fields due to divergence in the magnetization. As the MR head passes over the disk and reads the data stored thereon, the magnetic field from the permanently magnetized regions modulates the resistance of the MR head. A biasing signal, either current or voltage, typically is supplied to bias the magnetization of the MR head to a quiescent condition of optimum sensitivity and minimum distortion. If a biasing current is used, it is applied through the MR head. If a biasing voltage is used, it is applied across the MR head. A variation in the current or voltage can be sensed to read data values as the head passes over the disk.

#Each mode has different advantages and limitations. For example, current biasing has fewer noise problems and is usually adequately sensitive for performing read operations. However, current biasing, particularly with high current amplitude values, can cause premature aging of the MR head. Voltage biasing can be straight forward from a circuit standpoint, and is subject to noise issues and does not provide the sensitivity level desired in some applications.

#The invention is best understood by reference to the figures wherein references with like reference numbers indicate identical or functionally similar heads. In addition, the left-most digits refer to the figure in which the reference first appears in the accompanying figures.

#FIG. 1 illustrates a block diagram of a computer platform suitable for use with an embodiment of the invention.

#FIG. 2 is a block diagram of a disk drive exemplar.

#FIG. 1 is a block diagram of a computer platform 100 suitable for implementing an embodiment of the invention. The computer platform 100 is any acceptable computer system, including those using Intel and Intel compatible processors, a multiple virtual storage (MVS) platform available from International Business Machines, a UNIX computing system, or any Windows® or personal computer disk operating system (PC-DOS). A variety of computing platforms may be used to implement the present invention, including other high-end (enterprise and server class) computers, desktop computers, and mobile (laptop) computers. The computing platform 100 includes at least one data storage device, shown as disk drive 102, several peripheral devices 104, such as printers, etc., at least one central processing unit 106, a bus 108, a self-monitoring analysis and reporting technology (SMART) module 110, and a disk drive controller 112. The invention applies to any data storage read device and a disk drive is shown as an example of one acceptable use of the invention.

#The disk drive 102 typically is the primary data storage device used by the computing platform 100 to allow a user to record, store, and retrieve digital (or analog) data, operating systems, and other important information or files. The disk drive 102 contains electronics for exchanging data, controls, and signals with input/output (I/O) modules (peripheral devices), as well as electronics for controlling the disk read/write mechanism. Exemplar disk drives are capable of converting between the magnetic patterns on a moving disk surface and storing it as data in the disk drive's buffer. The disk drive 102 may be a single disk, multiple disks in a single drive, or several disk drives in a system. The disk drive 102 is described more fully below with reference to FIG. 2.

#The peripheral devices 104 are the equipment that provides the central processing unit 106 with outside communication. The peripheral devices 104 may also be referred to as peripheral equipment.