As of the publication of revision D of this datasheet, Texas Instruments has moved manufacturing of the die for MC3303 and MC3403 to a modern fabrication site. The two different die are referred to in this document as “Legacy” (previous fabrication site) and “New” die. The die origin can be separated from the “Chip Source Origin” (CSO) parameter in the shipping information. The old die CSO is “SHE”, for the new die CSO is “RFB”. The old die information is maintained in this datasheet for comparison purposes, but all new manufacturing has moved to the new die.