Hard disk protection diode?

Discussion in 'Electronic Repair' started by pimpom, Jan 25, 2009.

  1. pimpom

    pimpom Guest

    Does anyone have specific information about the protection device
    at the power supply inputs of hard disks?

    I assume that it's a zener diode or something similar in action
    such as an IC that acts like a precision zener diode. It's not
    difficult to see how such a device would provide protection
    against spikes, over-voltage and reverse voltage by shorting the
    power rail to ground and thereby triggering PSU shutdown.

    Devices in the BUX C*** series seem to be widely used, but I have
    not been able to find a datasheet or other detailed info. Can
    anybody shed some light on the matter?
     
    pimpom, Jan 25, 2009
    #1
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  2. I know I'm not directly answering your question, but...

    The socket and power cords are polarized. It would be extremely difficulty
    to insert the plug the wrong way.
     
    William Sommerwerck, Jan 25, 2009
    #2
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  3. pimpom

    pimpom Guest

    William Sommerwerck wrote:
    > I know I'm not directly answering your question, but...
    >
    > The socket and power cords are polarized. It would be extremely
    > difficulty to insert the plug the wrong way.


    Thanks for the reply. Yes, I expect that reverse voltage
    protection would be a secondary consideration. Its primary
    function would be protection against over-voltage, transient or
    sustained. Something like a crowbar or TVS device, but without
    the need for very low capacitance. A datasheet or identifying the
    manufacturer would be a big help.
     
    pimpom, Jan 25, 2009
    #3
  4. pimpom

    whit3rd Guest

    On Jan 25, 10:51 am, "pimpom" <> wrote:
    > Does anyone have specific information about the protection device
    > at the power supply inputs of hard disks?


    The most important reason a hard disk would need a protection
    device, is that the two power connections (motor power, 12V,
    and logic power, 5V) have a sequence condition requirement.

    So, the diode might clamp +12 to +5V so that a drop in the
    motor power (like, normal power turnoff) doesn't result in
    any short time during which the "+12" is actually at lower
    voltage than the "+5". Or, it might ensure that the +12
    supply never goes negative (which could happen if a
    motor is active when power is removed).

    Probably this diode is NOT a Zener type, which is
    relatively important: high current Zeners often fail short-circuit
    (which would halt the computer until disconnected).
     
    whit3rd, Jan 25, 2009
    #4
  5. pimpom

    Arfa Daily Guest

    "pimpom" <> wrote in message
    news:glicbp$3i2$...
    > Does anyone have specific information about the protection device at the
    > power supply inputs of hard disks?
    >
    > I assume that it's a zener diode or something similar in action such as an
    > IC that acts like a precision zener diode. It's not difficult to see how
    > such a device would provide protection against spikes, over-voltage and
    > reverse voltage by shorting the power rail to ground and thereby
    > triggering PSU shutdown.
    >
    > Devices in the BUX C*** series seem to be widely used, but I have not been
    > able to find a datasheet or other detailed info. Can anybody shed some
    > light on the matter?
    >
    >


    BUX * devices are usually high voltage transistors

    Arfa
     
    Arfa Daily, Jan 26, 2009
    #5
  6. pimpom

    Jim Yanik Guest

    "Arfa Daily" <> wrote in
    news:0S8fl.7569$2:

    >
    > "pimpom" <> wrote in message
    > news:glicbp$3i2$...
    >> Does anyone have specific information about the protection device at
    >> the power supply inputs of hard disks?
    >>
    >> I assume that it's a zener diode or something similar in action such
    >> as an IC that acts like a precision zener diode. It's not difficult
    >> to see how such a device would provide protection against spikes,
    >> over-voltage and reverse voltage by shorting the power rail to ground
    >> and thereby triggering PSU shutdown.
    >>
    >> Devices in the BUX C*** series seem to be widely used, but I have not
    >> been able to find a datasheet or other detailed info. Can anybody
    >> shed some light on the matter?
    >>
    >>

    >
    > BUX * devices are usually high voltage transistors
    >
    > Arfa
    >
    >
    >


    the PSU itself usually has overvoltage protection,where it really counts;on
    the +5 volt supply. The +12 is loosely regulated,and only runs the motor
    drive.some have "balance" nodes,that trigger SD if one or more of the
    supplies go too far outside a window.

    Then you don't need the expense of OV protection on every hard drive.

    --
    Jim Yanik
    jyanik
    at
    kua.net
     
    Jim Yanik, Jan 26, 2009
    #6
  7. pimpom

    Franc Zabkar Guest

    On Mon, 26 Jan 2009 00:21:34 +0530, "pimpom" <>
    put finger to keyboard and composed:

    >Does anyone have specific information about the protection device
    >at the power supply inputs of hard disks?


    >I assume that it's a zener diode or something similar in action
    >such as an IC that acts like a precision zener diode.


    Is it a transient voltage suppression diode?
    http://en.wikipedia.org/wiki/Transient_voltage_suppression_diode

    - Franc Zabkar
    --
    Please remove one 'i' from my address when replying by email.
     
    Franc Zabkar, Jan 26, 2009
    #7
  8. pimpom

    Franc Zabkar Guest

    On Sun, 25 Jan 2009 11:07:31 -0800, "William Sommerwerck"
    <> put finger to keyboard and composed:

    >I know I'm not directly answering your question, but...
    >
    >The socket and power cords are polarized. It would be extremely difficulty
    >to insert the plug the wrong way.


    It would require a very heavy hand, but I *have* seen it done.

    - Franc Zabkar
    --
    Please remove one 'i' from my address when replying by email.
     
    Franc Zabkar, Jan 26, 2009
    #8
  9. pimpom

    pimpom Guest

    whit3rd wrote:
    > On Jan 25, 10:51 am, "pimpom" <> wrote:
    >> Does anyone have specific information about the protection
    >> device
    >> at the power supply inputs of hard disks?

    >
    > The most important reason a hard disk would need a protection
    > device, is that the two power connections (motor power, 12V,
    > and logic power, 5V) have a sequence condition requirement.
    >
    > So, the diode might clamp +12 to +5V so that a drop in the
    > motor power (like, normal power turnoff) doesn't result in
    > any short time during which the "+12" is actually at lower
    > voltage than the "+5". Or, it might ensure that the +12
    > supply never goes negative (which could happen if a
    > motor is active when power is removed).
    >
    > Probably this diode is NOT a Zener type, which is
    > relatively important: high current Zeners often fail
    > short-circuit
    > (which would halt the computer until disconnected).


    I rather expect that it is similar to a zener diode in action but
    more sophisticated than a simple discrete zener, perhaps with
    more precise breakdown voltage, lower dynamic resistance and more
    surge current capacity. And a shorted device is not uncommon.
     
    pimpom, Jan 26, 2009
    #9
  10. pimpom

    pimpom Guest

    Franc Zabkar wrote:
    > On Sun, 25 Jan 2009 11:07:31 -0800, "William Sommerwerck"
    > <> put finger to keyboard and
    > composed:
    >
    >> I know I'm not directly answering your question, but...
    >>
    >> The socket and power cords are polarized. It would be
    >> extremely
    >> difficulty to insert the plug the wrong way.

    >
    > It would require a very heavy hand, but I *have* seen it done.
    >

    In any case, reversing a 4-pin Molex connector will not reverse
    the polarity. It will just juxtapose the +5 and +12V lines.
     
    pimpom, Jan 26, 2009
    #10
  11. pimpom

    pimpom Guest

    Arfa Daily wrote:
    > "pimpom" <> wrote in message
    > news:glicbp$3i2$...
    >> Does anyone have specific information about the protection
    >> device at
    >> the power supply inputs of hard disks?
    >>
    >> I assume that it's a zener diode or something similar in
    >> action such
    >> as an IC that acts like a precision zener diode. It's not
    >> difficult
    >> to see how such a device would provide protection against
    >> spikes,
    >> over-voltage and reverse voltage by shorting the power rail to
    >> ground and thereby triggering PSU shutdown.
    >>
    >> Devices in the BUX C*** series seem to be widely used, but I
    >> have
    >> not been able to find a datasheet or other detailed info. Can
    >> anybody shed some light on the matter?
    >>
    >>

    >
    > BUX * devices are usually high voltage transistors
    >

    Yes. But transistors have the BUX followed by numeric characters.
    These devices have a "C" before numerals.
     
    pimpom, Jan 26, 2009
    #11
  12. pimpom

    pimpom Guest

    Franc Zabkar wrote:
    > On Mon, 26 Jan 2009 00:21:34 +0530, "pimpom"
    > <>
    > put finger to keyboard and composed:
    >
    >> Does anyone have specific information about the protection
    >> device
    >> at the power supply inputs of hard disks?

    >
    >> I assume that it's a zener diode or something similar in
    >> action
    >> such as an IC that acts like a precision zener diode.

    >
    > Is it a transient voltage suppression diode?
    > http://en.wikipedia.org/wiki/Transient_voltage_suppression_diode
    >

    Could be. In fact, I mentioned that in my second post. What I
    find surprising and frustrating is that I have not been able to
    find any data on the BUX C*** series.
     
    pimpom, Jan 26, 2009
    #12
  13. pimpom

    Franc Zabkar Guest

    On Mon, 26 Jan 2009 15:45:37 +0530, "pimpom" <>
    put finger to keyboard and composed:

    >Franc Zabkar wrote:
    >> On Mon, 26 Jan 2009 00:21:34 +0530, "pimpom"
    >> <>
    >> put finger to keyboard and composed:
    >>
    >>> Does anyone have specific information about the protection
    >>> device
    >>> at the power supply inputs of hard disks?

    >>
    >>> I assume that it's a zener diode or something similar in
    >>> action
    >>> such as an IC that acts like a precision zener diode.

    >>
    >> Is it a transient voltage suppression diode?
    >> http://en.wikipedia.org/wiki/Transient_voltage_suppression_diode
    >>

    >Could be. In fact, I mentioned that in my second post. What I
    >find surprising and frustrating is that I have not been able to
    >find any data on the BUX C*** series.


    This forum discussion is about TVS devices in hard drives:
    http://forum.hddguru.com/seagate-barracuda-7200-st3300622a-300gb-ide-t9356.html

    The above discussion refers to this photo of a Seagate HDD with two
    TVS devices made by ON Semiconductor:
    http://forum.hddguru.com/download/file.php?id=562

    The parts have the following markings:

    ON logo QE
    R617

    ON logo 620
    LEM .

    I can't find exactly the same parts in ON's datasheets, but here are a
    few similar looking devices:

    Unidirectional Zener TVS 13V 600W (marking = LEN):
    http://www.onsemi.com/pub/Collateral/NSB13AN-D.PDF

    Zener Transient Voltage Suppressor 12V 600W (marking = LEK):
    http://www.onsemi.com/pub/Collateral/NSB12A-D.PDF

    400W Peak Power Zener Transient Voltage Suppressor 5V (marking = QA):
    http://www.onsemi.com/pub/Collateral/NSA5.0A-D.PDF

    600 Watt Peak Power Zener Transient Voltage Suppressor 5V (marking =
    6QE):
    http://www.onsemi.com/pub/Collateral/NS6A5.0A-D.PDF

    Here is a Vishay patent that discusses TVS devices with particular
    reference to their application in hard drives:
    http://www.freepatentsonline.com/WO2008002421.html

    - Franc Zabkar
    --
    Please remove one 'i' from my address when replying by email.
     
    Franc Zabkar, Jan 26, 2009
    #13
  14. pimpom

    Franc Zabkar Guest

    On Tue, 27 Jan 2009 06:13:23 +1100, Franc Zabkar
    <> put finger to keyboard and composed:

    >The above discussion refers to this photo of a Seagate HDD with two
    >TVS devices made by ON Semiconductor:
    >http://forum.hddguru.com/download/file.php?id=562
    >
    >The parts have the following markings:
    >
    > ON logo QE
    > R617
    >
    > ON logo 620
    > LEM .


    600 Watt Peak Power Zener Transient Voltage Suppressor, 12V,
    Unidirectional, p/n SMBJ12AON (marking = LEM):
    http://www.icbase.com/English/ic_search/just.asp?urlftp=/ONS/ONS26380605.pdf

    The "QE" marking belongs to a 1SMA5.0AT3, 400 Watt Peak Power Zener
    Transient Voltage Suppressor:
    http://www.datasheetarchive.com/pdf-datasheets/Datasheets-23/DSA-454313.html

    ON TVS/Zener Device Data Book:
    http://www.mosaico-eng.com.br/arquivos/Data-Sheet Zener.pdf

    - Franc Zabkar
    --
    Please remove one 'i' from my address when replying by email.
     
    Franc Zabkar, Jan 26, 2009
    #14
  15. pimpom

    Franc Zabkar Guest

    On Mon, 26 Jan 2009 15:19:08 +0530, "pimpom" <>
    put finger to keyboard and composed:

    >Arfa Daily wrote:
    >> "pimpom" <> wrote in message
    >> news:glicbp$3i2$...
    >>> Does anyone have specific information about the protection
    >>> device at
    >>> the power supply inputs of hard disks?
    >>>
    >>> I assume that it's a zener diode or something similar in
    >>> action such
    >>> as an IC that acts like a precision zener diode. It's not
    >>> difficult
    >>> to see how such a device would provide protection against
    >>> spikes,
    >>> over-voltage and reverse voltage by shorting the power rail to
    >>> ground and thereby triggering PSU shutdown.
    >>>
    >>> Devices in the BUX C*** series seem to be widely used, but I
    >>> have
    >>> not been able to find a datasheet or other detailed info. Can
    >>> anybody shed some light on the matter?
    >>>
    >>>

    >>
    >> BUX * devices are usually high voltage transistors
    >>

    >Yes. But transistors have the BUX followed by numeric characters.
    >These devices have a "C" before numerals.


    The BU? marking code appears to be used by ST Microelectronics in
    their SMBJ series 600W Transil (TVS) range.

    See page 2 of the datasheet:
    http://www.st.com/stonline/products/literature/ds/5616.pdf

    The BUX marking isn't listed, but it would appear that the "U"
    designates a unidirectional device.

    The "C" appears to be the manufacturing location, followed by a
    numeric YWW date code.

    - Franc Zabkar
    --
    Please remove one 'i' from my address when replying by email.
     
    Franc Zabkar, Jan 26, 2009
    #15
  16. pimpom

    Guest

    On Jan 25, 7:07 pm, "William Sommerwerck" <>
    wrote:
    > I know I'm not directly answering your question, but...
    >
    > The socket and power cords are polarized. It would be extremely difficulty
    > to insert the plug the wrong way.



    I have come across these shorted protection diodes on 2 occasions now,
    both on Digital Audio Recorders powered by external wall warts. If
    the wrong polarity wall wart is used, you can get the wrong polarity
    12Volts to the Hard Drive. This is shorted out by the diode, which
    eventually burns to a dead short protecting the drive. On both
    occasions replacing the diode restored the unit to fully operational.
    Good job they are there IMHO.



    Gareth.
     
    , Jan 28, 2009
    #16
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