Texas Instruments Corporation

Patrick G O'Farrell

William Robert Krenik

Kenneth James Maggio

Rolf Lagerquist

A circuit (10) and method for providing a drive current to a voice coil (20) to position a head (13) of a disk drive (14) includes driver circuitry (68, 70) for controlling currents flowing in the voice coil (20) and at least one sense current circuit (92), which may include FET devices (112, 114, 116, 118), for sensing and controlling the currents in a current path (26) of the driver circuit (10). Programmable circuitry (170) is connected to adjust at least one of the sense current circuits (112, 114 or 116, 118) to control a current flowing through the voice coil (20) to position the head (13) to a desired location. A trim capability is implemented by providing one or more trim FETs (145-148, 155-158) that are selectively connectable in parallel with current mirroring FETs (120, 126), which may be, for example, FETs connected to mirror a current in one of the current flow paths (26) of the drive circuit (10). By such selective connection, an effective channel width provided by the FET devices (120, 145-148 or 126, 155-158) can be selectively provided, thereby enabling the current in the voice coil (20), and therefore the position of the head (13) controlled by the voice coil (20) to be adjustable.

Trim circuitry and method for accuracy improvement in current sensing

A motor driver circuit (12) for providing drive signals to stator coils of a polyphase dc motor (10) includes a plurality of current paths, each connected between a supply voltage and a reference potential. Each current path includes two driver transistors (14,20, 16,22, 18,24), a node (A, B, C) of each of the stator coils being connectable between the driver transistors in respective current flow paths. A commutator (26) is connected to operate the driver transistors in a sequence in which drive currents are delivered for application in a predetermined sequence to the stator coils. A plurality of sensing transistors (32) are connected to produce a mirror current which mirrors a mirrored current in an associated driver transistor (20) in a respective current flow path. Circuitry (26) is provided which is responsive to the mirror currents of the sensing transistors to control the amplitudes of the currents in the associated driver transistor in a respective current flow path. At least one trim transistor (51-55) is connected in parallel with a respective one of the sensing transistors (50), and a programmable circuit (48) is connected to selectively activate the at least one trim transistor to adjust the amplitudes of the mirrored currents in the current flow path with which the sensing transistor with which the at least one trim transistor is associated.

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Plano, TX, United States of America

Patrick G O'Farrell