Abstract: A power system for a battery powered device can include a first stage power converter, a charge injector, and a bypass switch. The first stage power converter can be configured to have an input coupled to a battery and operable to convert a battery voltage to a level higher than a main voltage bus of the battery powered device. The charge injector can include an input coupled to the output of the power converter and an output configured to be coupled to the main voltage bus. The bypass can include one or more bypass switches operable to selectively couple an output of the power converter to the main voltage bus, bypassing the charge injector. The charge injector may be selectively operable as a current source configured to draw power from an output of the power converter and the battery to reduce voltage dips of the main voltage bus.

Abstract: Whether an audio output amplifier of an electronic device is connected through an accessory connector to a headphone or a self powered audio device is determined by sensing the signature of the input power signal in an input power line to a voltage regulator circuit that ultimately powers the amplifier. The signature is sensed flowing through a sense circuit that is in series in the input power line while the amplifier outputs a high power, inaudible signal to the connected device. The signature is output to a controller. The controller indirectly determines from the signature, whether the impedance of the connected device is that of (1) a headphone (speaker) for which a headphone amplifier is selected to provide more power for a lower impedance load, or (2) a self powered output device (“line in” input) for which a “line out” amplifier and isolation resistor are selected to drive a high capacitive load.

Abstract: Whether an audio output amplifier of an electronic device is connected through an accessory connector to a headphone or a self powered audio device is determined by sensing the signature of the input power signal in an input power line to a voltage regulator circuit that ultimately powers the amplifier. The signature is sensed flowing through a sense circuit that is in series in the input power line while the amplifier outputs a high power, inaudible signal to the connected device. The signature is output to a controller. The controller indirectly determines from the signature, whether the impedance of the connected device is that of (1) a headphone (speaker) for which a headphone amplifier is selected to provide more power for a lower impedance load, or (2) a self powered output device (“line in” input) for which a “line out” amplifier and isolation resistor are selected to drive a high capacitive load.

Abstract: Electronic devices may be provided with audio circuits and circuitry configured to support communications and test mode operations. During normal operation, a connector such as an audio connector may be inserted into a connector port in an electronic device. The audio connector may be associated with a headset or other accessory and may be used to carry audio signals. During test mode operations, a tester may be coupled to the connector port using an audio connector. The tester may generate voltages, resistances, time-varying signals, or other input that directs the device to configure switching circuitry to support testing. Monitoring circuitry in the device may be used to detect input from the tester. In response to detected input from the tester, the switching circuitry may be adjusted to couple a control circuit that supports test mode operations to the audio connector.

Abstract: Electronic devices may be provided with audio circuits and controller circuitry configured to support test mode operations. A connector such as a reversible connector may be inserted into a mating device connector in an electronic device. The reversible connector may be connected to the device connector in either a normal orientation or a reversed orientation in which the reversible connector is rotated 180° with respect to the normal orientation. During test mode operations, a tester may be coupled to the device connector using the reversible connector. The tester may generate voltages, resistances, time-varying signals, or other input that directs the device to configure switching circuitry to support testing. Monitoring circuitry in the device may be used to detect input from the tester. In response to detected input from the tester, the switching circuitry may be adjusted to couple the controller to the device connector.

Abstract: Electronic devices may be provided with audio circuits and circuitry configured to support communications and test mode operations. During normal operation, a standards-compliant connector such as an audio connector may be inserted into a connector port in an electronic device. The audio connector may be associated with a headset or other accessory and may be used to carry audio signals. During test mode operations, a nonstandard test connector may be inserted into the connector port. The electronic device may detect the presence of the nonstandard connector and may direct the electronic device to operate in a testing mode.