Abstract: A host electronic device may be coupled to an accessory electronic device. During normal operation, the host device may supply the accessory device with power over a power supply line. Back-powering events in which the accessory device delivers power to the host device may be prevented by interposing a protection transistor in the power supply line. A current mirror may be formed using the protection transistor and an additional transistor that produces a sense current proportional to the amount of current that is flowing through the power supply line. A current-to-voltage amplifier may produce a sense voltage that is proportional to the sense current. A bias circuit may be used to bias the sense current through the current mirror. A control circuit may compare the sense voltage to one or more reference voltages and turn off the protection transistor when appropriate to prevent back-powering of the host device.

Abstract: A host electronic device may be coupled to an accessory electronic device. During normal operation, the host device may supply the accessory device with power over a power supply line. Back-powering events in which the accessory device delivers power to the host device may be prevented by interposing a protection transistor in the power supply line. A current mirror may be formed using the protection transistor and an additional transistor that produces a sense current proportional to the amount of current that is flowing through the power supply line. A current-to-voltage amplifier may produce a sense voltage that is proportional to the sense current. A bias circuit may be used to bias the sense current through the current mirror. A control circuit may compare the sense voltage to one or more reference voltages and turn off the protection transistor when appropriate to prevent back-powering of the host device.

Abstract: A host electronic device may be coupled to an accessory electronic device. During normal operation, the host device may supply the accessory device with power over a power supply line. Back-powering events in which the accessory device delivers power to the host device may be prevented by interposing a protection transistor in the power supply line. A current mirror may be formed using the protection transistor and an additional transistor that produces a sense current proportional to the amount of current that is flowing through the power supply line. A current-to-voltage amplifier may produce a sense voltage that is proportional to the sense current. A bias circuit may be used to bias the sense current through the current mirror. A control circuit may compare the sense voltage to one or more reference voltages and turn off the protection transistor when appropriate to prevent back-powering of the host device.

Abstract: An electronic device may include protection circuitry coupled to a connector port. The connector port may be a reversible connector port that receives a mating reversible connector plug with either first or second orientations. The connector port may include contacts for receiving and/or transmitting signals during communications between the electronic device and the accessory device. The protection circuitry may monitor signals received at the contacts to determine whether transient or permanent connection faults exist. In response to determining that a connection fault exists at any of the contacts, the protection circuitry may electrically disconnect the faulty contacts from processing circuitry in the electronic device.

Abstract: Techniques for detecting mating and un-mating of a first connector with a second connector include providing a pulsed voltage signal at a contact of the second connector and measuring a rate of rise of voltage at the contact. If the measured voltage at the contact exceeds a threshold voltage during the time the pulsed voltage signal is applied, then it is concluded that the first connector is not present and not mated with the second connector. If the measured voltage is lower than or equal to the threshold voltage during the time of application of the voltage pulse, it is concluded that the first connector is present and mated with the second connector.

Abstract: Techniques for detecting mating and un-mating of a first connector with a second connector include providing a pulsed voltage signal at a contact of the second connector and measuring a rate of rise of voltage at the contact. If the measured voltage at the contact exceeds a threshold voltage during the time the pulsed voltage signal is applied, then it is concluded that the first connector is not present and not mated with the second connector. If the measured voltage is lower than or equal to the threshold voltage during the time of application of the voltage pulse, it is concluded that the first connector is present and mated with the second connector.

Abstract: An electronic device may include protection circuitry coupled to a connector port. The connector port may be a reversible connector port that receives a mating reversible connector plug with either first or second orientations. The connector port may include contacts for receiving and/or transmitting signals during communications between the electronic device and the accessory device. The protection circuitry may monitor signals received at the contacts to determine whether transient or permanent connection faults exist. In response to determining that a connection fault exists at any of the contacts, the protection circuitry may electrically disconnect the faulty contacts from processing circuitry in the electronic device.

Abstract: A host electronic device may be coupled to an accessory electronic device. During normal operation, the host device may supply the accessory device with power over a power supply line. Back-powering events in which the accessory device delivers power to the host device may be prevented by interposing a protection transistor in the power supply line. A current mirror may be formed using the protection transistor and an additional transistor that produces a sense current proportional to the amount of current that is flowing through the power supply line. A current-to-voltage amplifier may produce a sense voltage that is proportional to the sense current. A bias circuit may be used to bias the sense current through the current mirror. A control circuit may compare the sense voltage to one or more reference voltages and turn off the protection transistor when appropriate to prevent back-powering of the host device.

Abstract: A portable electronic device includes a radio frequency receiver; a radio frequency transmitter; and a processing system coupled with the receiver and transmitter. The processing system directs the receiver to scan a radio frequency spectrum for available radio channels over which the transmitter may transmit. The processing system may further direct the receiver to perform a second scan for radio channels which are actively transmitting information. The processing system then selects an available radio channel as the radio channel best suited for use by the transmitter to transmit information to the external audio system. The processing system may select a transmission frequency which is spectrally distant from the active radio channels and/or may take into account a transmission profile of the transmitter to select a frequency that does not interfere with the reception of incoming radio signals.

Abstract: A portable electronic device includes a radio frequency receiver; a radio frequency transmitter; and a processing system coupled with the receiver and transmitter. The processing system directs the receiver to scan a radio frequency spectrum for available radio channels over which the transmitter may transmit. The processing system may further direct the receiver to perform a second scan for radio channels which are actively transmitting information. The processing system then selects an available radio channel as the radio channel best suited for use by the transmitter to transmit information to the external audio system. The processing system may select a transmission frequency which is spectrally distant from the active radio channels and/or may take into account a transmission profile of the transmitter to select a frequency that does not interfere with the reception of incoming radio signals.