Patent ID: 8149191

Claim:
A method comprising: (a) providing a plurality of current source circuits (CSCs) and a plurality of strings of light emitting diodes (LEDs), wherein each CSC is coupled to supply a current through a corresponding one of the strings of LEDs, wherein some of the CSCs are part of a first integrated circuit and others of the CSCs are part of a second integrated circuit; (b) serially calibrating the plurality of CSCs to a single reference signal, wherein the serially calibrating involves: (b1) during a first time period calibrating a first of the CSCs of the first integrated circuit, wherein the single reference signal is a reference current signal, and wherein during the first time period the reference current signal is supplied from an external source, through a conductor, onto the first integrated circuit; and (b2) during a second time period calibrating a second of the CSCs of the second integrated circuit, and wherein during the second time period the reference current signal is supplied from the external source, through the conductor, onto the second integrated circuit, wherein the conductor is coupled to both the first and second integrated circuits; (c) determining on the second integrated circuit whether a voltage on the conductor has a predetermined characteristic; and (d) if the voltage is determined in (c) to have the predetermined characteristic then initiating said calibrating of the second of the CSCs of the second integrated circuit.