Patent ID: 8284925

Claim:
A jack detection circuit for detecting a jack or key state of an analog device or an analog signal outputted from the analog device so as to generate a digital signal, the jack detection circuit comprising: a switching circuit for forming an equivalent resistance in accordance with the jack or key state of the analog device or the analog signal outputted from the analog device; a transition circuit, coupled to the switching circuit, for generating a reference current in accordance with a first reference voltage and the equivalent resistance; and an AD converter, coupled to the transition circuit, for generating the digital signal in accordance with the reference current; wherein the reference current varies linearly corresponding to the variation of the equivalent resistance; wherein the transition circuit comprises a first reference voltage generator, coupled to the switching circuit, for generating the first reference voltage and correspondingly generating an initial reference current in accordance with the equivalent resistance, the first reference voltage, and a current mirror, coupled to the first reference voltage generator and the AD converter, for providing the reference current in accordance with the initial reference current.