A light emitting diode driving chip includes: a current regulating circuit arranged to selectively outputting four currents to four pins respectively; a current control circuit coupled to the current regulating circuit and a fifth pin, arranged to receive an adjusting signal at the fifth pin to control the four currents; a feedback voltage control circuit arranged to output a feedback voltage to a sixth pin according to a first specific voltage selected from four voltages corresponding to the four pins; and a protection circuit arranged to determine whether a voltage difference between a second specific voltage selected from the four voltages and the first specific voltage is larger than a threshold value. If the first specific voltage is larger than the threshold value, the protection circuit controls the current regulating circuit to stop conducting current to a specific pin corresponding to the first specific voltage.
