Electronic over stress detector circuit for magnetoresistive devices in data storage devices such as disc drives

• US 6,339,380 B1
• Filed: 04/07/2000
• Issued: 01/15/2002
• Est. Priority Date: 08/25/1999
• Status: Expired due to Fees

• Current Assignee: Seagate Technology LLC (Seagate Technology Holdings Plc)
• Original Assignee: Seagate Technology LLC (Seagate Technology Holdings Plc)
• Inventors: Wilson, David Robert
• Primary Examiner(s): Lefkowitz, Edward
• Application Number:
  US09/546,350
• Time in Patent Office: 648 Days
• Field of Search: 340/663, 340/662, 340/660, 340/657, 340/635, 324/537, 324/763, 324/764, 360/46, 360/66, 360/67
• US Class Current: 340/663
• CPC Class Codes: G11B 2005/001 Controlling recording characteristics of record carriers or transducing characteristics of transducers by means not being part of their structure
• CPC Class Codes: G11B 33/10 Indicating arrangements; Warning arrangements G11B15/04, G11B19/04, G11B27/34, G11B27/36 take precedence
• CPC Class Codes: G11B 5/012 Recording on, or reproducing or erasing from, magnetic disks G11B17/00, G11B19/00 take precedence
• CPC Class Codes: G11B 5/3166 Testing or indicating in relation thereto, e.g. before the fabrication is completed
• CPC Class Codes: G11B 5/40 Protective measures on heads, e.g. against excessive temperature G11B5/31 takes precedence; protection against wear G11B5/255 ; protective structure of the head: see under structures, e.g. G11B5/3106
• CPC Class Codes: G11B 5/455 Arrangements for functional testing of heads; Measuring arrangements for heads

Abstract

The circuit in accordance with the present invention monitors current signals between the preamplifier and the transducer in a data storage device such as a disc drive utilizing magnetoresistive transducers and/or giant magnetoresistive transducers. The detector circuit includes an amplitude section, a duration section, a frequency section, and an alarm section. The amplitude section has a comparator for detecting when a signal exceeds a predetermined voltage level. The duration section measures the time period that the comparator has an output signal. The frequency section measures the frequency of occurrence of comparator output signals. Each of the sections provides an input to the alarm section which provides an alarm signal condition if the amplitude section magnitude is too high, or the duration times amplitude is too high, or the frequency of occurrences of events is too high.

Claims

1. An electrical over stress detection circuit for detecting an over stress condition for a transducer in a data storage device during device manufacture which could adversely affect the read/write transducer in the device after device manufacture, the circuit comprising:

a reference voltage; and

an amplifier in a transducer preamplifier connected to the transducer and to a comparator, the comparator being connected to the reference voltage and to an output of the amplifier wherein the comparator provides a first output state if the amplifier output does not exceed the reference voltage, and provides a second output state indicating an over stress condition if the amplifier output exceeds the reference voltage.

2. The circuit according to claim 1 further comprising an integrator having an input connected to the comparator output for providing an alarm output signal.

3. The circuit according to claim 2 wherein the alarm output signal of the integrator is connected to a latch.

4. The circuit according to claim 3 wherein the amplifier is also connected to a variable resistance connected to the input of the integrator to vary a time constant of the integrator.

5. The circuit according to claim 1 wherein the amplifier output is connected through an analog to digital converter to a hold register for storing a signal magnitude and source address.

6. The circuit according to claim 1 wherein the transducer is a giant magnetoresistive transducer.

7. The circuit according to claim 6 further comprising an integrator having an input connected to the comparator output for providing an alarm output signal.

8. The circuit according to claim 7 wherein the alarm output signal of the integrator is connected to a latch.

9. The circuit according to claim 8 wherein the amplifier is further connected to a variable resistance connected to the input of the integrator to vary a time constant of the integrator.

10. The circuit according to claim 6 wherein the amplifier output is connected through an analog to digital converter to a hold register for storing a signal magnitude and source address for the giant magnetoresistive transducer.

11. A disc drive having a rotating disc and an actuator assembly adjacent the rotating disc for moving a transducer over the disc to read and write digital data from and to the disc, and a preamplifier circuit connected to the transducer, the disc drive comprising:

an electrical over stress detector circuit having an amplifier connected to the transducer and to a reference voltage, and a comparator connected to the amplifier and to the reference voltage wherein the comparator provides a first output state if the amplifier output does not exceed the reference voltage, and provides a second output state indicating an over stress condition if the amplifier output exceeds the reference voltage.

12. The disc drive according to claim 11 further comprising an integrator in the detector circuit having an input connected to the comparator output for providing an alarm output signal.

13. The disc drive according to claim 12 wherein the transducer is a giant magnetoresistive transducer.

14. The disc drive according to claim 13 wherein the amplifier in the detector circuit is connected to a variable resistance connected to the input of the integrator to vary a time constant of the integrator.

15. A disc drive having a rotating disc and an actuator assembly adjacent the disc operable to move a transducer over the disc to read and write digital data from and to the disc, the disc drive comprising:

a preamplifier circuit connected to the transducer for amplifying read signals from the transducer; and

an electrical over stress detector means connected in the preamplifier circuit for sensing an over stress condition that could compromise operation of the transducer in the disc drive, the over stress detector means comprising a comparator, wherein the comparator provides a first output state in the absence of an over stress condition and provides a second output state to indicate an over stress condition.