A method is provided for operating a magnetic field detector circuit, whereby the magnetic field detector circuit is operated alternately in an active state or in a sleep state and the magnetic field detector circuit has a magnetic field measuring device and a wake-up timer, whereby the magnetic field measuring device comprises a magnetic field sensor. In the active state, the magnetic field measuring device is operated with a supply voltage and an output signal is generated by the magnetic field sensor. The magnetic field detector circuit comprises a wake-up timer, whereby the wake-up timer is operated with the supply voltage in the sleep state and a wake-up signal is generated by the wake-up timer after a predetermined sleep interval, and the magnetic field measuring device changes from the sleep state to the active state.
