US 7,023,647 B2 · Fly height control for a read/write head in a hard disk drive

Abstract

A fly height controller (10FHC; 10FHC′) for controlling the fly height of a read/write head assembly (15) in a disk drive (20) is disclosed. A heat element resistor (30) is disposed within the read/write head assembly (15). The fly height controller (10FHC; 10FHC′) includes registers (32R, 32W) for storing digital data words corresponding to the desired drive levels to be applied to the heat element resistor (30) during read and write operations. The registers (32R, 32W) are selectively coupled to a steady-state digital-to-analog converter (DAC) (36), depending upon whether a read or write operation is occurring; the output of the steady-state DAC (36) is applied to a voltage driver (40), which in turn drives current into the heat element resistor (30). Overdrive and underdrive transistors (44P, 44N) are provided to overdrive and underdrive the input to the voltage driver (40) in transitions between read and write operations. An initial state register (50) receives a digital word indicating the desired current for the heat element resistor (30) when unselected; the output of the initial state register (50) is applied to an initial state DAC (52), which drives an initial state voltage driver (54). Control logic (35; 35′) controls whether the steady-state voltage driver (40) or initial state voltage driver (54) drives the heat element resistor (30). The fly height controller (10FHC′) may also be adapted to control the fly height of multiple read/write head assemblies (15) in a disk drive.

Claims26

Dependent claims

A circuit for controlling the fly height of a disk drive read/write head assembly by controlling a current applied to a heat element resistor in the read/write head assembly, comprising:

a first voltage driver, having an output coupled to a terminal, the terminal for coupling to the heat element resistor;
a read current input for receiving a read current signal corresponding to a desired read current;
a write current input for storing a write current signal corresponding to a desired write current;
and
control circuitry for coupling the read current signal and the write current signal to an input of the first voltage driver in read and write disk operations, respectively.

2 more elements

A circuit for controlling the fly height of a plurality of disk drive read/write head assemblies by controlling a current applied to a heat element resistor in each of the plurality of read/write head assemblies, comprising:

a plurality of output voltage drive circuits, each having an input, and each having an output coupled to a corresponding one of a plurality of terminals, each of the plurality of terminals for coupling to a corresponding one of the plurality of heat element resistors;
a read current input for receiving a read current signal corresponding to a desired read current;
a write current input for storing a write current signal corresponding to a desired write current;
a demultiplexer circuit, having a first input for receiving a steady-state current signal, having a plurality of outputs, each coupled to an input of one of the plurality of output voltage drive circuits, and having at least one control input;
and
control circuitry for coupling the read current signal and the write current signal to the input of the demultiplexer circuit as the steady-state current signal in read and write disk operations, respectively, and for controlling the demultiplexer circuit to apply the steady-state current signal to a selected one of the plurality of output voltage drive circuits responsive to a head select signal.

3 more elements

A method of controlling the fly height of a read/write head assembly in a disk drive, comprising:

connecting a first terminal to a first heat element resistor in a first read/write head assembly;
during at least a portion of a disk read operation, applying a first voltage to the first terminal;
during at least a portion of a disk write operation, applying a second voltage to the first terminal,
storing a read current value;
storing a write current value;
wherein the step of applying the first voltage comprises:
responsive to receiving a disk read enable signal, applying a signal corresponding to the read current value to a first voltage driver, the first voltage driver having an output coupled to the first terminal;
and wherein the step of applying the second voltage comprises:
responsive to receiving a disk write enable signal, applying a signal corresponding to the write current value to the first voltage driver.

6 more elements

Dependencies are inferred from the claim text.

Fly height control for a read/write head in a hard disk drive

Life of this patent

Fly height control for a read/write head in a hard disk drive

Life of this patent

Abstract

Claims26