A discrete power supply requires a number of external components to build: a PWM controller, switching power MOSFETs, input capacitors, output capacitors, and the power inductor. All of these components vary for each design. For example, if a system has 30 different power supply rails, the selection of these components must be done for each rail design, which makes the job of designing a power subsystem very challenging. The required man hours in development time, procurement, and PCB layout escalate as the number of power rails required increases.