The RT8800/B are general purpose multi-phase synchronous buck controllers dedicating for high density power supply regulation. The parts implement 2, and 3 buck switching stages operating in interleaved phase set automatically. The output voltage is regulated and controlled following the input voltage of FB pin. With such a single analog control, the RT8800/B provide a simple, flexible, wide-range and extreme cost-effective highdensity voltage regulation solutions for various high-density power supply application. The RT8800/B multi-phase architecture provide high output current while maintaining low power dissipation on power devices and low stress on input and output capacitors. The high equivalent operating frequency also reduces the component dimension and the output voltage ripple in load transient. RT8800/B implement both voltage and current loops to achieve good regulation, response and power stage thermal balance. The RT8800/B apply the time sharing DCR current sensing technology newly as well; with such a topology, the RT8800/B extract the DCR of output inductor as sense component to deliver a more precise load line regulation and better thermal balance capability. Moreover, the parts monitor the output voltage for overcurrent and over-voltage protection; Soft-start and programmable under-voltage lockout are also provided to assure the safety of power system.