The Entry Transponder (ET) IC combines the proven TI DST+ transponder with a sophisticated power management; it has an SPI interface to connect it to an external micro-controller, ideally suited for Remote Keyless Entry applications for automotive. The embedded DST+ transponder offers a high level of security through its encryption, mutual authentication and after-theft diagnosis features; it operates without battery. The power management features battery charge and battery check functions, which can be used for charging of the battery through the transponder LF field.