Patent ID: 8812757

Claim:
A calibration method for a universal serial bus system including a universal serial bus (USB) host end and a USB device end, the method comprising: processing a self-calibration of the USB host end and the USB device end separately to calibrate terminal resistors of the USB host end and the USB device end; upon processing the self-calibration, performing the steps of: providing a plurality of chirp JK pairs; detecting the plurality of chirp JK pairs, and loading a power on a terminal resistor of the USB device end which is coupled to a terminal resistor of the USB host end before a preset chirp JK pair is outputted, so as to change a voltage level of the chirp JK pairs; detecting a voltage level variation of the changed chirp JK pairs on a node; and processing an online calibration according to the voltage level variation, so as to maintain the voltage level of the changed chirp JK pairs within a preset range.