Patent ID: 8447556

Claim:
A magnetic field sensor, comprising: a magnetic field sensing element supported by a substrate, the magnetic field sensing element for generating a composite magnetic field signal comprising a measured-magnetic-field-responsive signal portion and a self-test-responsive signal portion, wherein the measured-magnetic-field-responsive signal portion is responsive to a measured magnetic field and the self-test-responsive signal portion is responsive to a self-test magnetic field; a self-test circuit comprising a self-test current conductor proximate to the magnetic field sensing element, the self-test current conductor for carrying a self-test current to generate the self-test magnetic field, wherein the self-test circuit further comprises a diagnostic request processor configured to control the self test current to be on or off in response to a diagnostic input signal received by the diagnostic request processor or to be indicative of a self test during one or more time periods in response to a control signal generated by the diagnostic request processor; and a processing circuit coupled to receive a signal representative of the composite magnetic field signal, configured to generate a sensor signal representative of the measured-magnetic field-responsive signal portion, and configured to generate at least one of a diagnostic signal representative of the self-test-responsive signal portion or a composite signal representative of both the measured-magnetic-field-responsive signal portion and the self-test-responsive signal portion.