Abstract: This application provides apparatus and methods for initiating tests in an interface circuit without using inputs of the interface circuit dedicated to initiating the tests. In an example, a test mode interface circuit can include a voltage comparator configured compare a first voltage to a second voltage, a ripple counter configured to count pulses from a processor when the voltage comparator indicates that the first voltage is greater than the second voltage, and wherein the test mode interface circuit is configured to provide a test mode enable signal and an indication of the a desired test mode an interface circuit that includes the test mode interface circuit.

Abstract: This document provides apparatus and methods for providing low-power operation of an interface circuit during an interval when a port of the interface circuit is in an uncoupled state.

Abstract: This document discusses, among other things, an audio jack detection circuit configured to be coupled to an audio jack receptacle of an external device. The audio jack detection circuit configured to receive to receive audio jack receptacle information, to disable an oscillator when the audio jack receptacle information indicates that the audio jack receptacle is empty, and to enable the oscillator when the audio jack receptacle information indicates that the audio jack receptacle includes an audio jack.