Disk drive with channel and preamp with dynamic write-current control for write head

Patent metadata

Field	Value
Publication number	US-9275656-B1
Application number	US-201514804063-A
Country	US
Kind code	B1
Filing date	Jul 20, 2015
Priority date	Jul 20, 2015
Publication date	Mar 1, 2016
Grant date	Mar 1, 2016

Abstract

Disk drives with a Channel System and Write Driver Preamp architecture that dynamically adjusts the write driver's signal wave-shape depending on the write data signal pattern are described. The wave-shape control signal is generated in the Channel and transmitted to the Write Driver Preamp. Embodiments of the invention provide discrete n-level overshoot amplitude control using amplitude-level modulated (AML) signal. One embodiment implements a look-ahead strategy overshoot amplitude control where the overshoot amplitude for each transition depends only on the subsequent (following) bits in the data stream and not on any previously recorded data.

First claim

The invention claimed is:

1. A disk drive comprising:
a disk with thin film magnetic material on a surface;
an inductive write head for selectively magnetizing portions of the magnetic material on the surface of the disk and creating magnetic transitions to record data bits;
a channel system that analyzes a set of data bits to be written on the disk to determine the set of magnetic transitions required to record the set data bits and generates for each transition a corresponding overshoot control signal that selects an overshoot amplitude level from a set of overshoot amplitude values that includes two or more predetermined values, the overshoot amplitude level being selected depending on detection of predetermined patterns of data bits following each magnetic transition with a preprogrammed delay between the write data and the overshoot control signal; and
a write driver preamplifier that receives one or more signals from the channel system signal that encode the magnetic transitions for the set of data bits and the corresponding overshoot control signal, and the write driver preamplifier generating an output signal for the inductive write head that applies the overshoot amplitude level based on the overshoot control signal.

2. The disk drive of claim 1 wherein the overshoot control signal received by the write driver preamplifier is encoded as an amplitude-level modulated (AML) signal.

3. The disk drive of claim 1 wherein the overshoot control signal received by the write driver preamplifier is encoded as an amplitude-level modulated (AML) signal that is part of a composite signal that includes a current-mode logic (CML) signal that encodes the data bits.

4. The disk drive of claim 1 wherein the write driver preamplifier generates a latch clock signal for a Trigger Sample Block from the write data transitions and the Trigger Sample Block generates an amplitude control signal for a write driver.

5. The disk drive of claim 4 wherein the Trigger Sample Block receives a signal from an amplitude-level demodulator that determines the overshoot amplitude.

6. The disk drive of claim 5 wherein amplitude-level demodulator receives an amplitude-level modulated (AML) signal from the channel system over a signal path that also carries a read signal.

7. The disk drive of claim 5 wherein amplitude-level demodulator receives an amplitude-level modulated (AML) signal from the channel system as part of a composite signal that includes a current-mode logic (CML) signal that encodes the data bits.

8. The disk drive of claim 1 wherein the write driver preamplifier includes a preset buffer that is pre-loaded with an overshoot amplitude control value for a subsequent write data transition.

9. The disk drive of claim 1 wherein the write driver preamplifier includes a first Trigger Sample Block for positive write currents and a second Trigger Sample Block for negative write currents are used, and a setup time between write data transitions is one time period (1T).

10. The disk drive of claim 1 wherein the set of overshoot amplitude values includes three discrete values corresponding to a nominal overshoot amplitude, a low overshoot amplitude that is less than the nominal overshoot amplitude and a high overshoot amplitude that is more than the nominal overshoot amplitude, and the nominal overshoot amplitude value is selected when a number of time periods until a next magnetic transition for the set of data bits is in a predetermined range, and the low overshoot amplitude value is selected when the number of time periods until the next magnetic transition is greater than the predetermined range, and the high overshoot amplitude value is selected when the number of time periods until the next magnetic transition is less than the predetermined range.

11. The disk drive of claim 1 wherein the set of overshoot amplitude values includes two discrete values corresponding to a nominal overshoot amplitude and a high overshoot amplitude that is more than the nominal overshoot amplitude, and the nominal overshoot amplitude value is selected when a number of time periods until a next magnetic transition for the set of data bits is greater than a predetermined value, and the high overshoot amplitude value is selected when the number of time periods until the next magnetic transition is less than or equal to the predetermined value.

12. A disk drive comprising:
a disk with thin film magnetic material on a surface;
an inductive write head for selectively magnetizing portions of the magnetic material on the surface of the disk and creating magnetic transitions to record data bits;
a channel system that analyzes a set of data bits to be written on the disk and generates a current mode logic (CML) signal that encodes a set of magnetic transitions required to record the set data bits and generates for each transition a corresponding amplitude-level modulated (AML) overshoot control signal that selects an overshoot amplitude level from a set of overshoot amplitude values that includes two or more predetermined values, the overshoot amplitude level being selected depending on detection of predetermined patterns of data bits following each magnetic transition with a preprogrammed delay between the write data and the overshoot control signal; and
a write driver preamplifier that receives one or more signals from the channel system signal that include the current mode logic (CML) signal and the amplitude-level modulated (AML) overshoot control signal, the write driver preamplifier including an Demodulator for the AML overshoot control signal that determines the corresponding overshoot amplitude level that is supplied to a Trigger Sample Block, the Trigger Sample Block being driven by a Latch Clock that is set by transitions in the current mode logic (CML) signal, and the write driver preamplifier generating an output signal for the inductive write head that applies the corresponding overshoot amplitude level based on the current mode logic (CML) signal and overshoot control signal from the Trigger Sample Block.

13. The disk drive of claim 12 wherein the one or more signals received by the write driver preamplifier from the channel system includes a composite signal that includes the current-mode logic (CML) signal and the amplitude-level modulated (AML) overshoot control signal.

14. The disk drive of claim 12 wherein the Demodulator receives the amplitude-level modulated (AML) overshoot control signal from the channel system over a signal path that also carries a read signal.

15. The disk drive of claim 12 wherein the write driver preamplifier includes a preset buffer that is pre-loaded with an overshoot amplitude control value for a subsequent write data transition.

16. The disk drive of claim 12 wherein the Trigger Sample Block includes a first unit for positive write currents and a second unit for negative write currents are used, and a setup time between write data transitions is one time period (1T).

17. The disk drive of claim 12 wherein the set of overshoot amplitude values includes three discrete values corresponding to a nominal overshoot amplitude, a low overshoot amplitude that is less than the nominal overshoot amplitude and a high overshoot amplitude that is more than the nominal overshoot amplitude, and the nominal overshoot amplitude value is selected when a number of time periods until a next magnetic transition for the set of magnetic transitions, and the low overshoot amplitude value is selected when the number of time periods until the next magnetic transition is greater than the predetermined range, a

Assignees

• HGST Netherlands BV

Inventors

• Contreras John
• Garzon Samir Y
• Hanson Weldon Mark
• Taratorin Alexander

Classifications

• G11B20/10388

  control of the read or write heads, e.g. tracking errors, defocus or tilt compensation · CPC title

• G11B5/09 Primary

  Digital recording · CPC title

• G11B20/10009

  Improvement or modification of read or write signals · CPC title

• G11B20/10018

  analog processing for digital recording or reproduction (G11B20/10037 - G11B20/10481 take precedence) · CPC title

• G11B5/02

  Recording, reproducing, or erasing methods; Read, write or erase circuits therefor · CPC title