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Need help identifying TI 6855A component

Discussion in 'Electronic Repair' started by Franc Zabkar, Nov 9, 2012.

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  1. Franc Zabkar

    Franc Zabkar Guest

    I'm trying to help the OP at the following thread:
    http://forum.hddguru.com/fried-pcb-newest-seagate-drive-where-the-eeprom-chip-t24422.html

    I'm fairly certain that the problem is a shorted TVS diode, but I'm
    curious as to the identify of a 16-pin chip with the following
    markings:

    6855A
    TI 271
    A1CJ

    It is located just below the 4-pin jumper block, and at about 10
    o'clock to the MCU (the largest IC).

    I suspect that it was made by Texas Instruments, and that it may be a
    step-down PWM regulator with integrated MOSFET and diode.

    A datasheet search at TI's web site found no items containing "6855".

    The board appears to have 5 switchmode supplies (there are 5
    inductors), with one being a -5V supply and the others probably being
    positive step-down regulators. One would provide +1.8V for the SDRAM
    and flash memory, while the others would provide the Vcore and Vio
    supplies for the MCU.

    - Franc Zabkar
     
  2. Franc Zabkar

    Franc Zabkar Guest

    The "271" looks like a data code, maybe week 1 of the 7th month
    (July), 2012.

    The date codes on other ICs include 228, 229, 1228, 231 which would be
    consistent.

    Could it be a Japanese part?

    - Franc Zabkar
     
  3. N_Cook

    N_Cook Guest

    Is it FQN-16 footprint? if so probably .cn origin
     
  4. Franc Zabkar

    Franc Zabkar Guest

  5. N_Cook

    N_Cook Guest

  6. N_Cook

    N_Cook Guest

  7. Franc Zabkar

    Franc Zabkar Guest

    It's from a Seagate hard drive. I doubt that Seagate would source
    their components from dubious outlets.

    Could it be "T1" (tee one) rather than TI (tee eye)?

    - Franc Zabkar
     
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