Need help identifying TI 6855A component

[Franc Zabkar]

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
--
Please remove one 'i' from my address when replying by email.

 

[Franc Zabkar]

On Fri, 09 Nov 2012 19:33:13 +1100, Franc Zabkar
<fzabkar@iinternode.on.net> put finger to keyboard and composed:

6855A
TI 271
A1CJ

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
--
Please remove one 'i' from my address when replying by email.

 

[N_Cook]

Franc Zabkar <fzabkar@iinternode.on.net> wrote in message
news:qq90a8lbcntqccjo21fcoaeqk1gijr81na@4ax.com...

On Fri, 09 Nov 2012 19:33:13 +1100, Franc Zabkar
fzabkar@iinternode.on.net> put finger to keyboard and composed:

6855A
TI 271
A1CJ

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
--
Please remove one 'i' from my address when replying by email.

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

 

[Franc Zabkar]

On Mon, 12 Nov 2012 12:16:12 -0000, "N_Cook" <diverse@tcp.co.uk> put
finger to keyboard and composed:

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

I don't have access to the actual board. All I have are the photos in
that thread ...

http://www.users.on.net/~fzabkar/HDD/6855A.jpg

- Franc Zabkar
--
Please remove one 'i' from my address when replying by email.

 

[N_Cook]

Franc Zabkar <fzabkar@iinternode.on.net> wrote in message
news:itp2a890o48fg4lr5bic3c9retlel251nu@4ax.com...

On Mon, 12 Nov 2012 12:16:12 -0000, "N_Cook" <diverse@tcp.co.uk> put
finger to keyboard and composed:

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

I don't have access to the actual board. All I have are the photos in
that thread ...

http://www.users.on.net/~fzabkar/HDD/6855A.jpg

- Franc Zabkar
--
Please remove one 'i' from my address when replying by email.

presumably these grey market "Texas Instr", complete with erroneous col
headers. Difficult to be sure they are QFN-16 in your pic

http://www.szspl-ic.com/en/IcStock.aspx?page=84&pp=TI

 

[N_Cook]

Franc Zabkar <fzabkar@iinternode.on.net> wrote in message
news:itp2a890o48fg4lr5bic3c9retlel251nu@4ax.com...

On Mon, 12 Nov 2012 12:16:12 -0000, "N_Cook" <diverse@tcp.co.uk> put
finger to keyboard and composed:

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

I don't have access to the actual board. All I have are the photos in
that thread ...

http://www.users.on.net/~fzabkar/HDD/6855A.jpg

- Franc Zabkar
--
Please remove one 'i' from my address when replying by email.

presumably these grey market "Texas Instr", complete with erroneous col
headers. Difficult to be sure they are QFN-16 in your pic

http://www.szspl-ic.com/en/IcStock.aspx?page=84&pp=TI

 

[Franc Zabkar]

On Tue, 13 Nov 2012 08:54:04 -0000, "N_Cook" <diverse@tcp.co.uk> put
finger to keyboard and composed:

presumably these grey market "Texas Instr", complete with erroneous col
headers.

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
--
Please remove one 'i' from my address when replying by email.