The MLX90109 is a single chip RFID transceiver for the 125kHz frequency range. It has been conceived for minimum system cost and minimum power consumption, offering all required flexibility for a state of the art AM transceiver base station. An external coil (L), and capacitor (C) are connected as a parallel resonant circuit, that determines the carrier frequency and the oscillator frequency of the reader. This eliminates zero modulation effects by perfect antenna tuning, and avoids the need for an external oscillator. The reader IC can easily be switched to power down by setting the antenna amplitude to zero. The MLX90109 can be configured to decode the transponder signal on-chip. In this case the decoded signal is available through a 2-wire interface with clock and data. For minimum interface wiring, the non-decoded transponder signal can also be made available on a single wire interface.