Universal serial bus device and charging and enumeration method

摘要

A universal serial bus device includes: a core circuit having a first pin and a second pin, and having an input impedance looking into the core circuit from the first pin and the second pin; and a charging control circuit, coupled to the core circuit, arranged for providing a voltage source having a predetermined voltage to one of the first pin and the second pin and for providing a current source having a predetermined current to the other of the first pin and the second pin; wherein the input impedance of the core circuit is configured to make the predetermined voltage and the predetermined current substantially intact when an external charger charges a battery device of the universal serial bus device.

主权项

1. A universal serial bus (USB) device, comprising:
a core circuit, having a first pin and a second pin, the core circuit having an input impedance looking into the core circuit from the first pin and the second pin; and a charging control circuit, coupled to the core circuit, comprising:
a voltage source, arranged for selectively coupling to one of the first pin and the second pin according to a switch control signal;wherein the input impedance of the core circuit is configured to make the voltage source substantially intact when the voltage source is coupled to one of the first pin and the second pin, and the input impedance is configurable according to the switch control signal;wherein the USB device is further coupled to an external charger and a battery device; and when the USB device is under a dead battery condition, the external charger provides a first supply voltage to the battery device to charge the battery device to make the battery device generate a battery output voltage, and the core circuit is arranged to be powered up by a second supply voltage derived from the battery output voltage generated by the battery device, rather than derived from the first supply voltage; and the switch control signal is generated in response to the second supply voltage.