Who Am I?
Troubleshooting and Repairing Electronics problem can be fun but when you come across this kind of Integrated Circuit (IC) that does not have any part number written or printed on it could make you frustrated. You just do not know what type of IC is it and the function of it unless you got the schematic diagram. The picture shown above have blank marking and not like others that have the part number removed and left out some blur marking on it (some use sand paper to purposely remove it). I have seen many UPS that the part number have been removed. The purpose of using ICs that do not have the marking, i believe is to prevent the design from being copied by another competitor and also not encouraging other technician to repair it. Your choice would be send the equipment back to the distributor or get a new set.
By the way we have to thanks to the manufacturers who did not remove the part number in most of the consumer electronic equipment otherwise as an electronic repairer we will have a hard time figuring it out the part number and its function. The photo above was taken from a remote control.