Unicorn part that I can't find in any database.

[Corwin_S]

Hi there,

Is anyone familiar with a 8 port surface mount chip that has SM858 YD5REAL written on it? I can't find this in any online database.

I recently had a phone charger stop working after I dropped it off a balcony, so I've been probing around with the circuit to see what got disconnected.

There are two boards that comprise the unit. One takes the power from the wall, and the other seemingly distributes it via usb ports. There are two wires that connect the two boards, which appear to originate out of the transformer.

The first board is receiving power no problem, but the second isn't.

There is a small surface mount chip in the center of the first board that has the part number listed above. All eight pins are at ground potential when probed, so I think it might be part of the problem.

Thanks,
Corwin

 

[davenn]

hi there
welcome

can you take a clearer pic of the chip looking straight down on the board so we can see what it is connected to
well lit and sharp

 

[Corwin_S]

Certainly!

 

[davenn]

Certainly!

yeah, that sorta helped
looking possibly like a dual FET

 

[Corwin_S]

That sounds like a good guess. In that case, it's probably the MOSFET for the switching converter.

If all the pins are at the same potential on that chip, and the secondary side of the xfmr is dead, which do you think is more likely to have failed due to the sudden impact from a relatively long free fall, the MOSFET or the xfmr?

 

[dorke]

A sudden impact would most likely damage the transformer not the IC.

Take a crisper photo of the IC,it is too blured to read the writing.
I think it is a PWM controller with an integrated switching MOSFET.

 

[Corwin_S]

It's blurred because the file is being compressed when it uploads. These letters are 100s of microns at best.

This is about the best I can do. It appears that two characters have been scratched off on the top right.

 

[davenn]

A sudden impact would most likely damage the transformer not the IC

agree with that comment

This is about the best I can do. It appears that two characters have been scratched off on the top right.

I do see where you listed the wrong part # in your opening post ... its SD858 not SM858
there could be one or two 3's on the end of that SD8583 or 85833 ??

tried searching using both with no luck

but still agree with dorke .... dropping the unit wouldn't kill the chip


Dave

 

[Corwin_S]

I found the part, the number is SD8585S.

It's a primary side regulator with a built-in MOSFET:
http://www.silan.com.cn/english/pro...=20140702013249635399057724628288&c=AC-DC转换电路

The page lists a block diagram, but it doesn't appear there is an actual datasheet (although I do not know Chinese).

 

[dorke]

Nice find,
Here (page 18) is this app diagram.
Start with checking for VDD to GND voltage I would expect something like 20V

 

[Corwin_S]

Fantastic! This is exactly what I needed.

 

[davenn]

be VERY VERY careful playing with this if you have voltage on it

depending on your mains voltage 120 or 220-240VAC, there will be anything between 180 and 300V on that top rail between the bridge out and the top of the transformer to the right