The PBL 3776/1 is a switch-mode (chopper), constant-current controller IC intended for controlling external transistors in a high current stepper motor application.The IC has two channels one for each winding of a two-phase stepper motor. The circuit is similar to Ericssons PBL 3775/1. PBL 3776/1 is equipped with a Disable input to simplify half-stepping operation. The PBL 3776/1 contains a clock oscillator, which is common for both driver channels, a set of comparators and flip-flops implementing the switching control, and two output sections each containing four outputs, two source and two sink, intended to drive an external H-bridge. Voltage supply requirements are +5 V for logic and +10 to +45 V for the outputs. The close match between the two driver channels guarantees consistent output current ratios and motor positioning accuracy.