The ATR4256 is a synthesizer IC for FM receivers and an AM up-conversion system in BiCMOS technology. Together with the AM/FM IC ATR4258 or ATR4255, it comprises a complete AM/FM car radio front-end, which is also recommended for RDS (Radio Data System) applications. It is controlled by a 3-wire bus and also contains switches and Digital to Analog Converters (DACs) for software-controlled alignment of the AM/FM tuner. The ATR4256 is the pin-compatible successor IC of U4256BM-R. Figure 1-1.