The M66503A is a constant current LED driver IC, whose output current is variable. The IC's functions include 16-bit serial input/parallel output shift register with output latch. The product uses Bi-CMOS process for highly accurate constant current driving, permitting high-efficiency LED driving without using a resistor that limits LED current. Settings for the LED drive current are made by an external resister, thereby ensuring a maximum output current of 30 mA, enough for anode-common LED driving. Furthermore, the pin configuration of the IC permits easier wiring on a printed board.