I probably found who is behind the unknown chip 980 YFC LM4FS1BH.

If you search for LM4FS1 you probably find one of the following manufactures Burr-Brown (BB), Chipcon, GrayChip, NSC (National Semiconductor), Harris (RCA Electronics Pte), all owned by Texas Instruments and Micron, as I did on this web page.

So it looks like it's a special version of a Cost-Effective System Management Controller Chip.

Hope that does help others to get more detailed informations.

Alle the best for 2014.

For anyone who is trying to take a 4. Generation iPod Touch produced 2012 late/2012, will have serious problems , as Apple did change the production towards glue and tape. They did especially tape the logic board onto the shield underside and if you are not aware of this, you definitely brake the flat cable connection between the volume buttons and the logic board. Also the volume button base plate is taped and NOT fixed with screws anymore. There are also more copper shields added to the device. The best would be, if iFixit does take apart the iPod Touch 4. Generation produced in 2012 and late/2012 as there are a lot less parts hold in place with screws. I would change the rating from difficult to extremely difficult.