The ATA5580 is an AES-128 based transponder device designed for automotive immobilizer applications and can be used as a companion device of the ATA5795 that combines both immobilizer and remote keyless entry functions in a car key fob. The ATA5580 consists of an ultra low power AVR MCU with 8K Flash and 2K EEPROM, an AES encryption unit, a 125kHz immobilizer front end block and an integrated LC tank. Battery supply is not required as it is powered via a magnetic field at 125kHz that is also used for the bidirectional data communication between the transponder and the base station located in a car. Thanks to its very low operating voltage of 1.9V (induced voltage), the ATA5580 operates reliably in metal environment where the coupling factor is often as low as 1%. Also, it has a built-in AES-128 cryptographic engine that, along with the optional open immobilizer protocol stack (CMMI certified), provides maximum security and fast authentication time. As an open-source solution, the AES-128 encryption-based protocol provides higher security than current proprietary protocols since peer reviewing increases  fault detection and enables interoperability between different semiconductor vendors. The ATA5580 is offered in an LGA-like plastic brick package.