Stmicroelectronics Gmbh

Elango Pakriswamy

Albino Pidutti

Axel Alegre De La Soujeole

Roberto Alini

Giuseppe Patti

A method and circuit are disclosed for controlling the write head of a magnetic disk storage device. The circuit includes a pull-up device coupled to a terminal of the write head, a current sink circuit which is coupled to the write head terminal and a bootstrap circuit coupled to the current sink circuit. When reversing the direction of current flow through the write head so that current is drawn from the write head from the write head terminal, the bootstrap circuit and the current sink circuit are activated. When the current in the write head nears and/or slightly surpasses the desired destination current level, the bootstrap circuit is deactivated and the pull-up device is thereafter immediately activated for a predetermined period of time.

Circuit and method for writing to a memory disk with a boosted voltage

A circuit includes a differential amplifier that generates a differential offset signal on its output terminals. The circuit also includes an offset compensator that has input terminals respectively coupled to the amplifier output terminals and a compensation terminal coupled to the differential amplifier. The compensator maintains the differential offset signal at a predetermined value, for example 0 V. When used in an integrated read-head preamplifier, such a circuit compensates for the nonzero head bias voltage, i.e., the preamplifier input offset voltage, without using a component that is external to the integrated preamplifier circuit.

Read-head preamplifier having internal offset compensation

A circuit and method to drive an H-bridge circuit is disclosed. The H-bridge circuit uses NMOS transistors for both the upper and lower sets of transistors. An inductive head is coupled between the terminals of the transistors. When a logic signal is received, it is boosted with a circuit including a capacitor and is used to drive one of the upper transistors. The upper transistor selected to be driven is responsive to the logic signal. A corresponding lower transistor is also driven, forcing current through the inductive head in a first direction. When the logic signal is received that is the complement of the first logic signal, the other upper and lower transistors turn on, thereby driving current through the inductive head in the other direction. Since all of the transistors in the H-bridge circuit are NMOS transistors, boosted driving circuits are used to quickly change the direction of the flux through the inductive head.

Method and apparatus to drive the coil of a magnetic write head

A circuit and method to drive an H-bridge circuit are disclosed. The H-bridge circuit uses NMOS transistors for both the upper and lower sets of transistors. An inductive head is coupled between the terminals of the transistors. When a logic signal is received, one of the upper transistors is driven. The upper transistor selected to be driven is responsive to the logic signal. A corresponding lower transistor is also driven, forcing current through the inductive head in a first direction. The driving circuit for the lower transistors includes a programmable circuit structured to capacitively couple the output of the driving circuit to a pull-up voltage, thereby allowing the amount of current forced through the inductive head to be maximized for optimum data transfer. Within the programmable voltage boost circuit are several logic gates, each coupled to a capacitor of differing value. When the circuit is manufactured, the inductive head is tested to determine the capacitance value to be coupled to the lower driving transistors for improved operation. Codes are stored on the chip that identify the corresponding logic gate or gates to obtain the selected capacitance. The selected logic gates are enabled when the H-bridge circuit is operational. The boosted driving circuits are used to quickly change the direction of the flux through the inductive head.

An H-bridge for applying a current to a coil of a write head assembly for writing data to a magnetic media includes two pair of two switchable transistors. Each pair of transistors is connected between a supply voltage and a reference potential and is adapted to be connected to the coil between the transistors of each pair for turning the transistors turned on and off in a sequence to control the direction of current flow in the coil. The upper transistors of each pair serves a switching transistor, and the lower transistors provide a mirrored referenced current to the coil. A pair of capacitors are connected to a control element of a respective associated one of the lower transistors, and switching circuitry is connected to the capacitors to selectively connect each of the capacitors to inject current into the control element of the respective associated lower transistor when the respective associated lower transistor is turned on. Also disclosed is a technique for adjusting the amount of boost current injected into the lower transistors.

Method and circuit for enabling rapid flux reversal in the coil of a

A method and apparatus, for applying a current to a coil of a write head assembly of a disk drive, or the like, to cause the flux within the coil to rapidly reverse, has an H-bridge having two pair of two switchable transistors. Each pair of the transistors is connected between a supply voltage and a reference potential, and is adapted to be connected to the coil between the two transistors of each pair. The two transistors of the first pair may be connected to receive a control signal to turn on complementary transistors of the first and second pair of transistors to selectively control current flow in the coil in first or second directions. A reference current source supplies a reference current, and one of the transistors in each of the first and second pairs of transistors is connected when turned on to mirror the reference current to control the currents in the coil. First and second parallel transistors are connected in parallel respectively with the mirror transistors, the first and second parallel transistors being connected to be turned on respectively by the control signal and the inverted control signal concurrently with the respective mirror transistor. A pair of timing elements turn off respective ones of the parallel transistors after a predetermined time so that when the parallel transistors are turned on, the current in the coil overshoots a value established by the mirror transistors.

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Santa Clara, CA, United States of America

Elango Pakriswamy