The L4974A is a step-down monolithic DC-DC Power Switching Regulator delivering 3.5A at a voltage variable from 5.1 to 40V. It is realized with BCD mixed technology, the device uses a DMOS output transistor to obtain very high efficiency and very fast switching times. It requires few external components. An efficient operation at switching frequencies up to 200KHz allows reduction in the size of external filter component.