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SCHOTTKY diode.. — Parallax Forums

SCHOTTKY diode..

RITESH KAKKARRITESH KAKKAR Posts: 254
edited 2011-02-01 07:14 in General Discussion
Hi, i have SMD shocky diode ic, but i don't understand it terminal.

Thanks.
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Comments

  • JLockeJLocke Posts: 354
    edited 2011-01-12 02:06
    I think you mean Schottky diode?

    Here's the Wikipedia link: http://en.wikipedia.org/wiki/Schottky_diode
  • RITESH KAKKARRITESH KAKKAR Posts: 254
    edited 2011-01-12 02:14
    Yaa, i know but the terminal shown in PDF is something different.
  • LeonLeon Posts: 7,620
    edited 2011-01-12 03:19
    It's a MOSFET with a diode in the same package. The anode and cathode connections are clearly identified, what is the problem?

    It's marked obsolete, BTW. Why are you using it?
  • RITESH KAKKARRITESH KAKKAR Posts: 254
    edited 2011-01-12 03:44
    It's a MOSFET with a diode in the same package. The anode and cathode connections are clearly identified, what is the problem?

    It's marked obsolete, BTW. Why are you using it?

    I have taken it frommy old STB dth, i study in class that it is used for high freq. switching.
    I will be helpful if you tell me more about this package.
    thanks.
  • stamptrolstamptrol Posts: 1,731
    edited 2011-01-12 05:07
    The package description shows that the unit is used in converters and other DC switching applications. The Schottkey diode works like a regular diode except it has much lower forward voltage drop and recovers from conducting state to non-conducting state much more rapidly than a normal diode. Very useful in rapidly switching inductive loads.

    It probably would have been used with the inductive components of a converter system.

    Google schottkey diode and have a look at the Wikipedia entry.

    The MOSFET part of the package is just an ordinary device with the naturally ocurring reverse diode shown.

    Cheers,
  • RITESH KAKKARRITESH KAKKAR Posts: 254
    edited 2011-01-12 05:42
    Please tell why the pin 1,2 & 8,7 are shorted, and how to know to mosfet current and voltage rating?
  • LeonLeon Posts: 7,620
    edited 2011-01-12 05:55
    The diodes are in parallel to increase the current rating, presumably.

    The data sheet will have the relevant ratings, try reading it!
  • stamptrolstamptrol Posts: 1,731
    edited 2011-01-12 09:31
    You can also go to the STMicroelectronics site and track down the device.
  • RITESH KAKKARRITESH KAKKAR Posts: 254
    edited 2011-01-12 20:32
    Leon wrote: »
    The diodes are in parallel to increase the current rating, presumably.

    How, the schematic shows only one diode with 4 terminals??
  • LeonLeon Posts: 7,620
    edited 2011-01-12 22:02
    The additional connections will increase the current capability.
  • RITESH KAKKARRITESH KAKKAR Posts: 254
    edited 2011-01-12 23:44
    hi, which additional connection are taking & how??
  • LeonLeon Posts: 7,620
    edited 2011-01-13 02:05
    See the diagram!! There are two connections to each end of the diode.
  • RITESH KAKKARRITESH KAKKAR Posts: 254
    edited 2011-01-13 04:39
    Hi, if you are talking about this, how it will increase the current capability, please tell.
    ScreenHunter_01 Jan. 04 16.21.jpg
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  • LeonLeon Posts: 7,620
    edited 2011-01-13 05:54
    Two connections instead of one!
  • RITESH KAKKARRITESH KAKKAR Posts: 254
    edited 2011-01-13 08:04
    But the diode is one!!
  • tonyp12tonyp12 Posts: 1,951
    edited 2011-01-13 08:12
    Having two pins, is the same as having a thicker wire.
    And it allows you to make a wider trace on the pcb so more electricty can go through.

    And using multi pins instead of one big wide one, allows the factory to use the same machinery that makes single pins.
    And probably helps with cooling with its air space.


    look at this one, it have 5pins for the same path to handle 180amp
    http://www.infineon.com/dgdl/IPB025N10N3+G_Rev2.03.pdf?folderId=db3a304313b8b5a60113cee8763b02d7&fileId=db3a30431ce5fb52011d1ab1d9d51349
  • LeonLeon Posts: 7,620
    edited 2011-01-13 08:13
    Two connections in parallel, though!

    Weren't you taught basic electrical theory at school?
  • ctwardellctwardell Posts: 1,716
    edited 2011-01-13 09:06
    Leon is grumpty today. :-)

    Tony has it right, the 5 pins make up one high current connection, the other high current connection is the tab. The gate of course only needs one pin.

    C.W.
  • RITESH KAKKARRITESH KAKKAR Posts: 254
    edited 2011-01-13 22:39
    ctwardell wrote: »
    Leon is grumpty today. :-)

    Tony has it right, the 5 pins make up one high current connection, the other high current connection is the tab. The gate of course only needs one pin.

    C.W.

    No, it's OK i was not absorbing as i was thinking that, little STB will take few mA then what the use of // connection.

    but i don't understand what the use of putting Schottky diode and MOSFET in STB??
  • ctwardellctwardell Posts: 1,716
    edited 2011-01-14 06:23
    Ritesh,

    Here is some detail on "fetky" devices, includes reasons why to combine both devices in one package.

    http://www.irf.com/product-info/fetky/

    C.W.
  • RITESH KAKKARRITESH KAKKAR Posts: 254
    edited 2011-01-14 07:38
    Thanks..!!.
  • Mike GreenMike Green Posts: 23,101
    edited 2011-01-14 08:55
    Look up Buck Regulator and Boost Regulator in the Wikipedia. It's very common in these regulators to require an MOSFET and a diode and, because these regulators are commonly used with low voltages, low voltage drop through the diode is important, so a Schottky diode is used.
  • RITESH KAKKARRITESH KAKKAR Posts: 254
    edited 2011-01-15 00:09
    Hi, i have 18V transformer, when i rectified it gives 21V (near by) and current is 3.5A.
    I want to calculate it's AC current, how??
  • RITESH KAKKARRITESH KAKKAR Posts: 254
    edited 2011-01-16 00:53
    reply, please.!!
  • LeonLeon Posts: 7,620
    edited 2011-01-16 02:46
    rms, peak or mean current?
  • RITESH KAKKARRITESH KAKKAR Posts: 254
    edited 2011-01-17 08:20
    Please tell in details, i want to learn your experience.!!
  • RITESH KAKKARRITESH KAKKAR Posts: 254
    edited 2011-01-19 04:54
    please reply.!!
  • LeonLeon Posts: 7,620
    edited 2011-01-19 05:12
    What do you want to know?
  • RITESH KAKKARRITESH KAKKAR Posts: 254
    edited 2011-01-19 06:45
    Leon wrote: »
    rms, peak or mean current?

    this.
  • kwinnkwinn Posts: 8,697
    edited 2011-01-19 07:34
    RITESH KAKKAR wrote: »
    No, it's OK i was not absorbing as i was thinking that, little STB will take few mA then what the use of // connection.

    but i don't understand what the use of putting Schottky diode and MOSFET in STB??


    The diode/mosfet combination is designed for use in DC switching applications. In those applications the transistor usually switches current on/off to an inductor and the diode blocks reverse current. This type of circuit has high peak currents even though the average current may be low. Having multiple leads results in lower resistance for the high peak currents as well as better heat removal for the chip.
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